Supplements

WHAT THE EVIDENCE SAYS

The starting point is a pharmacological difference that is rarely explained and that accounts for the whole dispute. Taken by mouth, plasma vitamin C is tightly controlled by absorption and renal excretion and does not exceed roughly 300 µM ^[1]. Intravenous administration bypasses that control and reaches concentrations of about 20 mM, tens of times higher (NCI PDQ) ^[1]. This means two things at once: studies of oral and intravenous vitamin C effectively concern two different interventions and conclusions must not be transferred between them; and reaching a high concentration is not itself evidence of clinical benefit — it is evidence that the drug arrived.

The clinical evidence is sparse and early. NCI lists phase I trials in pancreatic cancer (14 participants combined with gemcitabine and erlotinib; 9 participants with stage IV disease), a phase I/IIA trial in 27 patients with stage III/IV ovarian cancer, and more recent phase II trials in 47 patients with castration-resistant prostate cancer and 34 patients with stage IV pancreatic cancer ^[1]. These are small, mostly single-arm studies designed to assess safety and feasibility rather than efficacy ^[1]. A reported median overall survival of 12 months in pancreatic cancer means little without a comparison group — patients enrolled in early-phase trials are typically in better general condition than the average patient with that diagnosis ^[1].

The results are mixed and must be presented as such: some studies report fewer chemotherapy side effects and better quality of life, others show no anticancer effect at all ^[1][2]. Findings in cell cultures and animal models are considerably more promising than findings in humans — which in oncology is the rule rather than the exception and is not in itself an argument for use ^[1].

STRENGTH OF THE EVIDENCE

Low. There is not a single large randomised trial answering whether intravenous vitamin C prolongs life or delays progression ^[1]. Absence of evidence of benefit is not evidence of absence of benefit — but neither is it a basis for paying for a therapy presented as causal treatment. The regulatory position is unambiguous: the FDA has not approved IV vitamin C as a cancer treatment ^[1][2].

WHO THIS ENTRY IS FOR

For people who have been offered — usually privately, outside the public system — vitamin C infusions as part of cancer treatment, and for their families. It does not concern dietary vitamin C or the treatment of diagnosed deficiency (scurvy), which are separate matters entirely.

INTERACTIONS WITH CANCER TREATMENT

Plasma cell myeloma and bortezomib is the best-documented signal of harm. Vitamin C binds bortezomib and blunts its activity: in preclinical work, bortezomib combined with oral vitamin C produced greater tumour volume than bortezomib alone (NCI PDQ) ^[1]. Anyone treated with bortezomib should discuss any vitamin C supplementation with their physician.

A broader caution applies to all antioxidants taken during chemotherapy and radiotherapy, whose mechanism relies partly on oxidative damage to tumour cells. The best data come from an observational study nested in SWOG S0221 (JCO 2020; 1,134 breast cancer patients): antioxidant supplement use before and during chemotherapy was associated with numerically worse outcomes (recurrence adjHR 1.41; 95% CI 0.98–2.04), but the confidence interval includes 1.0, so this is NOT statistically significant and must not be presented as proof of harm ^[3]. What reached significance in that study were vitamin B12 and iron, not antioxidants ^[3].

CONTRAINDICATIONS — NO ROOM FOR UNDERSTATEMENT HERE

NCI lists them explicitly ^[1][2]. Glucose-6-phosphate dehydrogenase (G6PD) deficiency: high doses may cause haemolysis, and people with this inherited disorder should not be given them ^[1][2]. Kidney disease: kidney failure has been reported after treatment with IV vitamin C ^[2]. Predisposition to kidney stones: people likely to develop stones should not be treated with IV vitamin C ^[2]. Haemochromatosis and other iron-overload states: vitamin C increases iron absorption ^[2]. Outside these situations, infusions were generally well tolerated in clinical trials, with mild reported effects (increased urination, thirst, nausea, vomiting, chills) ^[1][2].

THE SCOPE OF WHAT WE WRITE HERE

We give no doses, infusion schedules or concentration targets — that would be advice for an individual, and cancer3.ai is an information portal, not a clinic. Nor do we rule on whether an infusion is acceptable alongside standard treatment in an individual case; that is for the treating team, which knows the diagnosis, renal function and the full medication list. We write about one thing: how strong the evidence is and where the known safety limits lie.

Sources

1. National Cancer Institute — Intravenous Vitamin C (PDQ®), Health Professional Version 2025: cancer.gov ↗
2. National Cancer Institute — Intravenous Vitamin C (PDQ®), Patient Version 2024: cancer.gov ↗
3. Ambrosone CB et al. — Dietary Supplement Use During Chemotherapy and Survival Outcomes of Patients With Breast Cancer Enrolled in a Cooperative Group Clinical Trial (SWOG S0221), Journal of Clinical Oncology 2020: europepmc.org ↗

WHAT THE EVIDENCE SAYS

The starting point is solid and uncontested: gut bacteria help shape the response to immune checkpoint blockade ^[1][3]. The controversy begins with the practical question — whether that relationship can be exploited by swallowing a capsule.

The key clinical paper appeared in Science in 2021 (Spencer et al., PMID 34941392) ^[1]. It assessed faecal microbiota profiles, dietary habits and use of commercially available probiotic supplements in melanoma patients receiving immunotherapy, alongside parallel preclinical work ^[1]. The authors report: "Higher dietary fiber was associated with significantly improved progression-free survival in 128 patients on ICB, with the most pronounced benefit observed in patients with sufficient dietary fiber intake and no probiotic use ^[1]." In mouse models the same picture was reproduced: a low-fibre diet or probiotic administration impaired the response to anti-PD-1-based therapy, with a lower frequency of interferon-gamma-positive cytotoxic T cells in the tumour microenvironment ^[1].

The picture is not uniform, however, and honesty requires the other side. A 2025 review (Frontiers in Immunology, PMID 41472726) collects data in which specific strains — Bifidobacterium, Lactobacillus, Clostridium butyricum, Akkermansia muciniphila — enhanced checkpoint inhibitor responses in animal models of melanoma, lung and colorectal cancer, while in early-phase clinical studies and retrospective cohorts, particularly in lung and renal cancer, probiotic use was associated with improved progression-free and overall survival ^[2]. The same authors state the limitation plainly: "most clinical data are observational, and the field lacks standardized probiotic formulations and dosing protocols ^[2]."

The second, far better established part of this topic is ANTIBIOTICS. The National Cancer Institute describes a European study as follows: "Patients who had taken antibiotics for an infection within 2 months before or 1 month after starting immunotherapy with checkpoint inhibitors did not live as long as patients who didn't take antibiotics ^[3]." A caveat must accompany that sentence: this is an observation, not an instruction to forgo antibiotics. Infection in a cancer patient can be life-threatening, and only the treating physician decides whether antibiotic therapy is warranted.

STRENGTH OF THE EVIDENCE

Low to moderate — and unevenly distributed. The association between microbiota composition and immunotherapy efficacy is well documented. The claim that taking a probiotic improves treatment outcomes is supported by NOT ONE conclusive randomised trial; the available clinical data are observational and therefore burdened by the fact that people who reach for supplements differ from those who do not in many ways at once ^[2]. Moreover, two good sources point in opposite directions — the Science paper signals possible harm, the 2025 review possible benefit ^[1][2]. In that situation the only honest answer is "we do not know", rather than picking whichever side sounds more agreeable.

WHO THIS ENTRY IS FOR

For patients treated with checkpoint inhibitors (most often in melanoma, lung cancer and renal cancer) and their families, who encounter reports that "the microbiome decides whether immunotherapy works" and wonder whether to buy a probiotic. It does not cover probiotics used for other indications under medical supervision, nor faecal microbiota transplantation, which remains an investigational procedure conducted only within clinical trials.

INTERACTIONS WITH CANCER TREATMENT

First — possible weakening of immunotherapy. The Science paper indicates that in melanoma patients taking probiotics the benefit of high fibre intake was less pronounced, and animal models showed an outright worse response to anti-PD-1 after probiotic administration ^[1]. This is a signal, not proof, but a signal pointing toward harm in a treatment that for many patients is the only effective option.

Second — infection risk. Probiotic strains are live microorganisms, and bloodstream infections caused by those very strains have been described in immunocompromised people ^[4][5]. A case series in Emerging Infectious Diseases (2024) on Clostridium butyricum bacteraemia after probiotic use noted that most patients had compromised immune systems ^[4]. In another series in the same journal (2026), among 5,034 children who received probiotics after cardiac surgery, 6 developed bacteraemia with a probiotic strain; all had central venous catheters ^[5]. The population differs from an oncological one, but the mechanism — translocation of live bacteria from the gut and catheter contamination — is the same, and patients on chemotherapy combine both risk factors: neutropenia and a vascular port. Saccharomyces fungaemia after administration of an S. boulardii preparation has also been described.

Third — antibiotics. As above: the association with shorter survival is documented, but the practical conclusion is "tell your treating team that you are starting immunotherapy", not "avoid antibiotics" ^[3].

WHAT THIS MEANS FOR DIET

The only element of this topic backed by clinical data suggesting benefit is DIETARY FIBRE from food, not a supplement from the pharmacy ^[1]. That is consistent with the catalogue entry on the Mediterranean diet, and the two entries are worth reading together.

THE SCOPE OF WHAT WE WRITE HERE

We give no strains, doses or regimens, because no standardised preparation of demonstrated efficacy exists, and naming a specific one would amount to advice for an individual ^[2]. We do not describe faecal microbiota transplantation beyond noting that it is investigational. cancer3.ai is an information portal — whether to take any supplement during cancer treatment is decided by the treating team.

Sources

1. Spencer CN et al. — Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response, Science 2021: europepmc.org ↗
2. Jani CT et al. — Leveraging beneficial microbiome-immune interactions via probiotic use in cancer immunotherapy, Frontiers in Immunology 2025: europepmc.org ↗
3. National Cancer Institute — Gut Bacteria Influence Effectiveness of a Type of Immunotherapy, Cancer Currents Blog 2018: cancer.gov ↗
4. Sada RM et al. — Clostridium butyricum Bacteremia Associated with Probiotic Use, Japan, Emerging Infectious Diseases 2024: europepmc.org ↗
5. Wang X et al. — Case Series of Bacteremia Associated with Probiotic Use in Children after Cardiac Surgery, China, Emerging Infectious Diseases 2026: europepmc.org ↗

WHAT THEY ARE MEANT TO DO

Chemotherapy and pelvic radiotherapy damage the intestinal epithelium and change the composition of the gut flora, and diarrhoea is a common reason for dose reduction or treatment interruption. Probiotics, that is live bacteria (most often Lactobacillus and Bifidobacterium), are intended to restore that flora and strengthen the gut barrier ^[2].

WHAT THE POOLED ANALYSES SHOW

• a systematic review of 29 randomised trials: lower incidence of diarrhoea with probiotics (RR 0.67; 95% CI 0.47–0.95) and a stronger effect with synbiotics (RR 0.51; 95% CI 0.29–0.89) ^[1];
• a meta-analysis of 18 trials and 1,526 patients with colorectal cancer: RR 0.51 (95% CI 0.40–0.64) and shorter duration of diarrhoea ^[3];
• a meta-analysis of 14 trials during fluoropyrimidine- or irinotecan-based chemotherapy: RR 0.40 (95% CI 0.27–0.60), NNT 3–5, meaning in theory one case of diarrhoea avoided per 3–5 people treated ^[4];
• a meta-analysis of 8 trials and 753 patients with leukaemia: OR 0.39 (95% CI 0.26–0.57) ^[8].

WHY WE STILL DO NOT WRITE THAT PROBIOTICS WORK: The largest and best-designed trial in this field — a multicentre, double-blind, placebo-controlled phase 3 study in 233 patients with colorectal cancer receiving irinotecan — failed its primary endpoint ^[5]. Grade 3–4 diarrhoea occurred in 7.9% of those taking a mixture of Bifidobacterium BB-12 and Lactobacillus rhamnosus GG versus 11.8% on placebo (p=0.38); diarrhoea of any grade in 41.2% versus 46.2% (p=0.51). The authors stated plainly that the results indicate a LACK of benefit. This is the classic pattern in which an effect shrinks as trial quality rises: many small trials show benefit, one large trial does not confirm it. In that situation the more cautious reading is the correct one.

WHAT THE GUIDELINES SAY

The MASCC/ISOO panel "suggests" that probiotics containing Lactobacillus species be used to prevent diarrhoea in patients receiving chemotherapy and/or radiotherapy for a pelvic malignancy, at level of evidence III ^[6]. This is the weakest category of recommendation and a narrow population — it is not a recommendation for every person with cancer.

WHEN PROBIOTICS SHOULD NOT BE TAKEN WITHOUT TALKING TO A DOCTOR:

• profound neutropenia, haematopoietic stem-cell transplantation, immunosuppressive treatment;
• mucositis of the gastrointestinal tract, a damaged gut barrier, a central venous catheter;
• ongoing immune-checkpoint immunotherapy (a separate question — see the entry "Probiotics and immunotherapy").

SAFETY: In the phase 3 trial no infection caused by the strains used was observed ^[5]. The risk is nonetheless not zero: a case has been described of a patient with advanced lung cancer in whom a bacterium from a probiotic fermented-milk drink caused a bloodstream infection, and the strain cultured from blood was genetically identical to the strain in the product ^[7]. The precondition was a combination of two factors: reduced immunity and a breach in the gastrointestinal wall.

WHAT THESE RESULTS DO NOT SAY

The absence of a proven benefit from probiotics does not mean that treatment-related diarrhoea does not need treating — on the contrary, it is a complication that can force chemotherapy to be interrupted and requires management agreed with the treating team. Nor do these results say anything about probiotics as a way of treating the cancer itself; none of the studies discussed tested that.

Sources

1. [1] Rachmawati et al. — The Role of Probiotics, Prebiotics, and Synbiotics for Reducing Chemotherapy-Induced Gastrointestinal Toxicity, Rom J Intern Med 2026 (29 RCT): europepmc.org ↗
2. [2] Salehi et al. — Gut microbiome dysbiosis and cancer: a systematic review on the emerging role of probiotics in oncology, Crit Rev Oncol Hematol 2026: europepmc.org ↗
3. [3] Yang et al. — Efficacy and safety of probiotics in preventing chemotherapy-related diarrhea in colorectal cancer, Medicine 2025 (18 RCT, n=1526): europepmc.org ↗
4. [4] Siritientong et al. — Oral probiotic supplementation to alleviate diarrhea induced by fluoropyrimidines or irinotecan-based chemotherapy, Complement Ther Med 2025 (14 RCT w metaanalizie): europepmc.org ↗
5. [5] Mego et al. — Randomized double-blind placebo-controlled multicenter phase III study of prevention of irinotecan-induced diarrhea by a probiotic mixture (BB-12 + LGG), Front Oncol 2023 (n=233): pmc.ncbi.nlm.nih.gov ↗
6. [6] Lalla et al. — MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy, Cancer 2014 (sugestia, poziom dowodów III): acsjournals.onlinelibrary.wiley.com ↗
7. [7] Lacticaseibacillus paracasei bacteremia secondary to esophageal invasion by pleomorphic carcinoma — case report, BMC Infect Dis 2026: europepmc.org ↗
8. [8] Chen et al. — Can probiotics reduce chemotherapy-induced complications in leukemia patients?, Nutr Clin Pract 2026 (8 RCT, n=753): europepmc.org ↗

WHY THIS ENTRY EXISTS

Cannabis is among the most widely self-administered products used by people with cancer, and the information circulating outside medicine blends two entirely different claims: that it helps tolerate treatment, and that it treats the cancer. The first has partial support in evidence; the second has none ^[1][2]. That distinction is the substance of this entry.

SYMPTOMS: WHERE THE EVIDENCE IS STRONGEST. The 2024 American Society of Clinical Oncology (ASCO) guideline reviewed 13 systematic reviews and 5 additional primary studies ^[1]. The highest quality of evidence (moderate) was found for cannabinoids in refractory chemotherapy-induced nausea and vomiting, and specifically for licensed drugs rather than herbal cannabis ^[1].

• Dronabinol (synthetic THC) was approved for this indication in 1986 ^[2].
• Nabilone is a second available synthetic THC analogue ^[2].
• Nabiximols (Sativex, 1:1 THC:CBD) are approved in Canada for symptomatic relief of pain in advanced cancer ^[2].

For herbal cannabis itself, rigorous clinical trial data in these indications are lacking - what exists is largely patient surveys ^[2].

APPETITE AND WASTING

Here the picture is weaker than common belief suggests. Dronabinol's indication was extended in 1992 to anorexia associated with HIV infection, but clinical trials showed no statistically significant weight gain - patients did report improved appetite ^[2]. Improved hunger and weight gain are not the same thing, and in cancer cachexia it is the latter that counts (see the separate entry on nutrition in cachexia).

TREATING THE CANCER

NO DATA. The US National Cancer Institute PDQ summary states plainly that clinical trials of medicinal cannabis are limited and that the FDA has not approved cannabis as a treatment for any medical condition ^[2]. Evidence of antitumour activity comes exclusively from laboratory and animal work (apoptosis, inhibition of angiogenesis in glioma, breast and colorectal models) and has not been confirmed in humans ^[2]. On that basis the ASCO guideline strongly recommends against using cannabis or cannabinoids as cancer-directed treatment outside a clinical trial, citing very low quality evidence and poorer outcomes observed in patients using these products during immunotherapy ^[1].

INTERACTIONS WITH CANCER TREATMENT - THE ESTABLISHED PART

Cannabinoids interact with the hepatic cytochrome P450 enzyme system, through which a large share of anticancer drugs is metabolised ^[2]. The NCI warns that highly concentrated CBD oils could through this mechanism increase toxicity or decrease the effectiveness of treatment ^[2]. For a sense of scale: in a study of 24 patients receiving irinotecan or docetaxel, cannabis herbal tea did not significantly influence exposure to or clearance of these drugs ^[2] - so the risk concerns concentrated preparations above all, not every form of cannabis. The practical conclusion is single: cannabinoid use must be disclosed to the treating team, because without that information the interaction risk cannot be assessed.

INTERACTIONS WITH IMMUNOTHERAPY - THE CONTESTED PART

Here the data are outright contradictory and must be presented as such.

• The biological premise raises concern: THC produced immunosuppression and enhanced tumour growth in immunocompetent mice ^[2].
• The ASCO guideline cites poorer clinical outcomes in patients using cannabis during immunotherapy ^[1].
• Yet a pooled analysis of individual patient data from four Canadian Cancer Trials Group studies (684 patients on durvalumab plus tremelimumab, with or without chemotherapy; 65 patients, 9.5%, used cannabinoids and 32 did so at baseline) found no harm: immune progression-free survival was longer in cannabinoid users (10.91 versus 8.31 months; HR 0.60; 90% CI 0.36-1.00; p=0.05), overall survival did not differ significantly (14.23 versus 11.30 months; HR 0.81; 90% CI 0.51-1.27; p=0.35), and there were no differences in response rate or in immune-related adverse events ^[3]. The authors write that the finding supports the safe use of cannabinoids alongside combination immune checkpoint inhibitor therapy ^[3].

WHAT THESE DATA DO NOT SAY

The CCTG analysis is retrospective: dose, route and THC-to-CBD ratio were unknown, the number of users was small and most likely understated through under-reporting ^[3]. Most users had non-small cell lung cancer (41.5%) or pancreatic cancer (40.0%), so the result does not transfer automatically to other diagnoses ^[3]. A positive association between cannabinoid use and longer time to progression does NOT mean cannabinoids improve immunotherapy outcomes - they may simply not harm them, and the difference may reflect the characteristics of patients who reach for them. Nor did any of the cited studies examine whether cannabis affects survival under other treatment regimens.

WHAT THIS MEANS FOR THE READER

Cannabinoids in licensed drug form have a documented place in symptom control, above all in refractory nausea and vomiting ^[1][2]. They are not a cancer treatment and must not replace or delay cancer treatment ^[1][2]. Decisions on starting or continuing them, on the form of the preparation and on interaction risk belong to the physician managing the treatment, who knows the patient's full regimen.

Sources

1. Braun IM, Bohlke K, Abrams DI i wsp. — Cannabis and Cannabinoids in Adults With Cancer: ASCO Guideline, Journal of Clinical Oncology 2024;42(13):1575-1593: ascopubs.org ↗
2. National Cancer Institute — Cannabis and Cannabinoids (PDQ), Health Professional Version: cancer.gov ↗
3. Effects of cannabinoids on immune checkpoint inhibitor response: CCTG pooled analysis of individual patient data, Immunotherapy 2025 (PMID 40184324): pubmed.ncbi.nlm.nih.gov ↗

WHY PEOPLE REACH FOR IT

Green tea is a beverage, not a drug, and that is precisely why its extract feels like a risk-free choice. Preparations standardised for epigallocatechin gallate (EGCG) are sold over the counter as antioxidants and weight-loss support ^[1]. A patient drinking a few cups a day and a patient taking an extract capsule are in two different situations — and that distinction is the core of this entry.

WHAT THE ONCOLOGICAL EVIDENCE SHOWS — SIGNALS IN BOTH DIRECTIONS:

• prevention: data are mixed, with possible benefit suggested for oral premalignant lesions and in populations at high risk of liver and colorectal cancer ^[1];
• prostate cancer: a blend containing green tea showed protective effects after treatment, but high-dose combination supplementation was associated with an ELEVATED incidence of prostate cancer in high-risk men ^[1]; long-term EGCG did not prevent recurrence ^[1];
• breast cancer: reduced recurrence risk has been reported, but regular consumption may elevate risk in some postmenopausal women ^[1];
• ovarian cancer: EGCG did not prevent recurrence ^[1];
• treatment side effects: limited data indicate EGCG may reduce radiation-induced oesophagitis in lung cancer patients and radiation dermatitis ^[1].

WHAT FOLLOWS FROM THIS PICTURE

This is not the profile of a preparation with proven anticancer activity. It is the profile of a substance whose effect depends on dose, formulation and clinical setting, and which in part of the research turned out opposite to expectation.

INTERACTIONS WITH CANCER TREATMENT — THE MOST IMPORTANT PART:

• BORTEZOMIB and other boronic acid-based proteasome inhibitors: EGCG and other polyphenols can inhibit their therapeutic effect ^[1]. This concerns the backbone of multiple myeloma treatment, so the supplement may reduce the efficacy of therapy;
• IRINOTECAN: EGCG inhibits biliary elimination, prolongs half-life and increases the risk of toxicity ^[1];
• PALBOCICLIB: decreased bioavailability in animal models ^[1];
• TAMOXIFEN: increased oral bioavailability, although a clinical trial did not confirm the interaction ^[1];
• NINTEDANIB: 21% reduction in bioavailability ^[1];
• anticoagulants and antiplatelet drugs: vitamin K antagonism at high intake ^[1];
• CYP3A4 and UGT substrates, verapamil, nadolol, rosuvastatin and atorvastatin — documented changes in drug exposure ^[1].

SAFETY: Common effects are nausea, stomach pain, sleep disruption and headache ^[1]. The serious concern is liver injury: hepatotoxicity has been documented at doses from 800 mg EGCG daily, with case reports of jaundice and acute hepatitis after green tea extracts ^[1]. At high doses (800–1600 mg EGCG daily) elevated liver enzymes, rectal bleeding and indigestion have also been described ^[1]. MSKCC lists contraindications: pregnancy and breastfeeding, stomach ulcers, and use on an empty stomach; the preparation should be discontinued if liver symptoms develop ^[1].

WHAT THIS ENTRY DOES NOT SAY

We give no doses and no regimen — any decision about a supplement during cancer treatment belongs to the treating physician, who knows the regimen and the patient's liver status. Nor do we claim that green tea as a drink is harmful: the reported liver events and most interactions concern concentrated EXTRACTS, not an ordinary infusion.

WHAT TO TELL THE TREATING TEAM

That an extract is being taken, the EGCG dose stated on the packaging, and every other supplement — especially before starting bortezomib, irinotecan or the targeted agents listed above.

Sources

1. [1] Memorial Sloan Kettering Cancer Center — About Herbs: Green Tea (dowody kliniczne, hepatotoksycznosc od 800 mg EGCG na dobe, interakcje z bortezomibem, irynotekanem, palbocyklibem, tamoksyfenem i nintedanibem): mskcc.org ↗

WHERE THE QUESTION COMES FROM

The reasoning that leads a patient to the vitamin shelf is logical and not at all naive: cancer treatment also damages healthy cells, and antioxidants protect cells from oxidative damage, so they ought to reduce collateral harm. NCI describes this motivation directly: antioxidants are taken by many cancer patients because it is thought that the substances will protect and repair healthy cells damaged by cancer therapy ^[1].

WHERE THAT REASONING BREAKS DOWN

Numerous anticancer agents generate reactive oxygen species, which decrease antioxidant levels, damage DNA and cause cancer cell death ^[1]. This is not a side effect of treatment — it is its MECHANISM. A preparation that blunts that mechanism may therefore blunt the treatment itself. The very property meant to protect a healthy cell also protects a cancer cell, and the supplement does not tell one from the other.

WHAT THE TRIALS SHOWED — HEAD AND NECK CANCER: Two randomised controlled trials assessed alpha-tocopherol (vitamin E) at 400 IU daily during radiation therapy ^[1]. The results:

• higher risk of tumour relapse,
• increased all-cause mortality,
• a decrease in cancer-free survival ^[1].

These are randomised trials, the strongest form of evidence available on this question, and they point to HARM rather than to absence of benefit.

WHAT THE STUDIES SHOWED — BREAST CANCER:

• a 2019 study: postmenopausal breast cancer survivors using antioxidant supplements (selenium, multivitamins, zinc, vitamins A, C and E) during chemotherapy or radiation had an increased risk of total mortality and worsened recurrence-free survival ^[1];
• a 2020 study: use of antioxidants (vitamins A, C, E; carotenoids; coenzyme Q10) during treatment with cyclophosphamide, doxorubicin and paclitaxel was associated with an increase in the hazards of recurrence and death; the result was not statistically significant but trended in the same direction as the previous one ^[1].

Both are observational and therefore do not establish causation — their value lies in independently pointing the same way as the randomised trials.

HOW NCI SUMS IT UP

This evidence gives reason to use these supplements with caution and indicates that more research on this topic is needed ^[1]. For many specific antioxidant supplements there is insufficient information to determine whether they are safe and effective ^[1].

WHAT THIS ENTRY DOES NOT SAY

• it does not concern antioxidants present in FOOD. Vegetables and fruit supply the same compounds in incomparably smaller amounts and in a different form; the problem described here concerns concentrated preparations;
• it does not concern preparations taken to correct a documented DEFICIENCY, for example in anaemia or proven vitamin D deficiency — that is a separate clinical situation decided by a physician;
• it contains no recommendation for any individual and gives no doses. The decision to stop or continue a supplement during treatment belongs to the treating physician.

WHAT TO TELL THE TREATING TEAM

About every vitamin or mineral preparation being taken, with the dose stated on the packaging — including multivitamins, which are rarely reported because they are not thought of as medicines. A conversation before chemotherapy or radiotherapy begins is a cheaper solution than stopping a preparation halfway through treatment.

Sources

1. [1] National Cancer Institute — Cancer Therapy Interactions With Foods and Dietary Supplements (PDQ), Health Professional Version (mechanizm reaktywnych form tlenu; dwa badania z losowym doborem z alfa-tokoferolem 400 j.m. w nowotworach glowy i szyi; prace Jung 2019 i Ambrosone 2020 w raku piersi; stanowisko o ostroznosci): cancer.gov ↗

WHAT LAETRILE IS

Laetrile is a purified form of amygdalin, a cyanogenic glycoside found in the pits of many fruits and in raw nuts ^[1]. It is sometimes sold as vitamin B17, although no vitamin classification recognises that designation ^[1]. The cyanide released from the molecule is regarded by advocates of the preparation as its principal anticancer component ^[1].

WHAT THE CLINICAL TRIAL SHOWED

The decisive data come from an NCI-sponsored phase II trial that enrolled 179 patients with various cancers, predominantly of the breast, colon and lung ^[1]. Among the 178 treated patients:

• ONE patient met response criteria, with a partial response lasting 10 weeks ^[1];
• 54% had measurable disease progression by the end of the intravenous course ^[1];
• seven months after completing therapy, ALL patients had disease progression ^[1];
• 7% reported improved work capacity and 20% reported symptomatic relief, but that relief did not persist ^[1].

Laetrile has shown little anticancer activity in animal studies and none in human clinical trials ^[1].

WHY THE ROUTE OF ADMINISTRATION CHANGES THE RISK

Cyanide is released from the molecule only under the action of beta-glucosidase enzymes, present in intestinal bacteria and in some commonly eaten plants ^[1]. Blood cyanide levels were therefore not elevated after intravenous administration but were elevated after oral therapy, and poisoning occurs far more frequently with oral use ^[1]. In animal studies, germ-free rats showed no effects from oral laetrile, whereas animals with normal gut flora showed signs of cyanide poisoning including lethargy and convulsions ^[1].

INTERACTIONS THAT INCREASE THE DANGER

Toxicity rises with concurrent consumption of ^[1]:

• raw almonds and crushed fruit pits,
• foods containing beta-glucosidase: celery, peaches, bean sprouts, carrots,
• high-dose oral vitamin C.

A case of life-threatening cyanide toxicity following ingestion of amygdalin together with vitamin C has been reported ^[1]. This combination is particularly troubling because both substances tend to be taken by the same people, as two elements of a single self-treatment strategy — precisely where the risk is greatest.

WHAT POISONING LOOKS LIKE

Adverse effects mirror the picture of cyanide poisoning: nausea, vomiting, headache, dizziness, liver damage, low blood pressure, fever, ataxic neuropathies, drooping eyelids, mental confusion, coma and death ^[1].

LEGAL STATUS

Laetrile is not approved for use in the United States; in 1980 the Supreme Court upheld a federal ban on interstate shipment ^[1]. It continues to be manufactured and administered, mainly in Mexico and in some clinics in the United States ^[1].

WHAT THIS ENTRY DOES NOT SAY

It is not a recommendation for any individual, nor a judgement on decisions already taken. Anyone taking laetrile, or considering taking it, should tell their treating physician — not least because the symptoms of cyanide poisoning can be mistaken for side effects of cancer treatment, and telling them apart determines what is done next. Decisions about cancer treatment are made by the specialist physician.

Sources

1. National Cancer Institute — Laetrile/Amygdalin (PDQ) Health Professional Version: cancer.gov ↗

WHY PEOPLE TAKE IT

Silymarin, a mixture of flavonolignans from milk thistle seeds, has a firm reputation as a liver-protective agent. Patients most often start it on their own initiative when liver function tests rise during chemotherapy ^[1].

WHAT THE EVIDENCE SHOWS

Memorial Sloan Kettering summarises the data cautiously: these are SMALL studies rather than decisive clinical trials ^[1]. They suggest:

• reduced chemotherapy-induced liver injury in children with acute lymphoblastic leukaemia and in patients with non-metastatic breast cancer,
• reduced radiotherapy-induced mucositis in patients with head and neck cancer,
• reduced chemotherapy-induced peripheral neuropathy and hand-foot syndrome (oral and topical forms),
• benefit in radiodermatitis in patients with breast cancer (topical form).

What the evidence does NOT show: silymarin does not treat cancer, does not replace any part of oncological treatment, and there are no data that it improves survival.

INTERACTIONS WITH CANCER TREATMENT

This is the most important part of this entry:

• milk thistle INHIBITS cytochrome CYP3A4, the enzyme that metabolises a large share of anticancer drugs, and can therefore change their concentrations ^[1];
• it modulates UGT enzymes, which per MSK may increase side effects of drugs metabolised by that route ^[1];
• it may decrease the clearance of sirolimus ^[1];
• a case of INR rising from 2.64 to 4.12 was reported in a patient on warfarin ^[1];
• cases of pancreatitis were reported with concomitant haloperidol or risperidone ^[1].

CONTRAINDICATIONS AND ADVERSE EFFECTS

Do not use if allergic to plants of the daisy/ragweed family. At high doses, increases in bilirubin and liver enzymes have been described — the opposite of the expected effect. Cutaneous reactions have also been reported: pruritus, rash, urticaria ^[1].

WHAT THIS MEANS

A supplement that looks like a neutral herbal add-on sits directly on the metabolic pathway of cancer drugs. Whether to take it during treatment is decided by the treating physician, who knows the full medication list. This entry is not medical advice.

Sources

1. Memorial Sloan Kettering Cancer Center — About Herbs: Milk Thistle: mskcc.org ↗

WHY PEOPLE TAKE IT

Reishi (lingzhi) is the best known of the so-called medicinal mushrooms, sold as an “immune-boosting” product and as “support during cancer”. It comes as powder, capsules and spore extracts ^[1].

WHAT THE EVIDENCE SHOWS

Memorial Sloan Kettering summarises the data as SMALL clinical studies in which reishi increased plasma antioxidant capacity and affected immune and tumour responses ^[1]. That is not enough to claim efficacy: there is no evidence that reishi treats cancer, prolongs survival, or replaces any part of oncological treatment. MSK also notes findings in the opposite direction — a reishi extract showed toxic effects in leukocytes ^[1].

A SIGNAL THAT MUST NOT BE OVERLOOKED

Patients undergoing treatment for gastrointestinal cancer who took reishi spore supplements had HIGHER levels of the tumour marker CA72-4 ^[1]. In practice this means the supplement may distort the follow-up tests the physician uses to judge how treatment is going.

INTERACTIONS WITH CANCER TREATMENT

• anticoagulants and antiplatelet drugs — reishi can increase bleeding risk ^[1];
• immunosuppressants — reishi enhances the immune response, working against the purpose of such treatment ^[1];
• drugs metabolised by cytochrome P450 — in vitro, reishi polysaccharides inhibited CYP2E1, CYP1A2 and CYP3A ^[1].

SAFETY. Cases of liver injury after powdered reishi have been reported, including one DEATH from fulminant hepatitis ^[1]. Reported adverse effects include nausea, insomnia, dry mouth, constipation, pruritus and vertigo ^[1].

WHAT THIS MEANS

“Natural” and “immune-boosting” does not mean neutral for treatment. Any decision about taking a mushroom preparation during cancer treatment belongs to the treating physician, who knows the full medication list. This entry is not medical advice.

Sources

1. Memorial Sloan Kettering Cancer Center — About Herbs: Reishi Mushroom: mskcc.org ↗

WHY PEOPLE TAKE IT

Glutamine is an amino acid absorbed from food, also synthesised by the body and stored mainly in muscle and lungs ^[1]. In oncology it is bought chiefly for mucositis, chemotherapy-induced peripheral neuropathy, gastrointestinal side effects and muscle weakness ^[1].

WHAT THE EVIDENCE SHOWS

Memorial Sloan Kettering states that studies SUGGEST glutamine or its derivatives are useful against mucositis, and that it may help prevent numbness and tingling caused by oxaliplatin and vincristine; intravenous glutamine also reduced chemotherapy-induced nausea, vomiting and diarrhoea in patients with gastric or colorectal cancer ^[1]. Findings from cachexia trials are MIXED ^[1].

WHAT THE GUIDELINES SAY — AND WHY THAT OUTWEIGHS SINGLE TRIALS. The 2014 MASCC/ISOO guidelines carried a recommendation AGAINST intravenous glutamine for the prevention of oral mucositis in patients receiving high-dose chemotherapy for haematopoietic stem cell transplantation ^[2]. The 2019 update identified new evidence but judged it inadequate and conflicting, and for that reason issued NO guideline for glutamine at all ^[3]. That is the honest state of knowledge: not “it works”, not “it does not work”, but “the evidence is too weak to recommend anything”.

A SEPARATE CONCERN, INDEPENDENT OF EFFICACY. Glutamine transporters are upregulated in tumour cells and glutamine may promote their growth and survival, so supplementation during cancer requires careful consideration ^[1].

INTERACTIONS WITH CANCER AND OTHER TREATMENT

• lactulose — glutamine may reduce its ammonia-lowering effect ^[1];
• methotrexate — glutamine may increase tumour retention of methotrexate, potentially enhancing its effect ^[1].

SAFETY. Reported effects include peripheral oedema, gastrointestinal symptoms, headache, fever and infections ^[1]. One case report documented severe abdominal pain with liver damage requiring discontinuation ^[1].

WHAT THIS MEANS

Glutamine is often presented as a harmless “building block” because the body makes it naturally. The evidence does not support that framing, and in one specific setting (intravenous form, stem cell transplantation) scientific societies explicitly advised against it. Any decision about supplementation during cancer treatment belongs to the treating physician, who knows the full medication list. This entry is not medical advice.

Sources

1. Memorial Sloan Kettering Cancer Center — About Herbs: Glutamine: mskcc.org ↗
2. Lalla RV i wsp. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy. Cancer 2014: acsjournals.onlinelibrary.wiley.com ↗
3. Elad S i wsp. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy (aktualizacja 2019). Cancer 2020: acsjournals.onlinelibrary.wiley.com ↗

WHY PEOPLE TAKE IT

Coenzyme Q10 (ubiquinone) is involved in cellular respiration and energy production ^[1]. It is sold mainly for heart disease, high cholesterol, statin-induced muscle pain, migraine, Parkinson's disease and infertility ^[1]. In oncology it is often bought by patients receiving anthracyclines — out of concern for the heart — and by people looking for a remedy for fatigue.

WHAT THE EVIDENCE SHOWS IN CANCER PATIENTS

The most important signal for patients is a warning, not an encouragement: antioxidant supplementation including CoQ10 before and during treatment was associated with an INCREASED hazard of recurrence in breast cancer patients ^[1]. In patients on tamoxifen, CoQ10 appeared to lower inflammatory cytokine levels ^[1], but that is a biological result, not proof of clinical benefit. Preliminary studies on cancer-related fatigue are MIXED ^[1]. Protection against doxorubicin toxicity was described in a murine model ^[1] — that is, not in humans.

WHY “ANTIOXIDANT” IS NOT AN ADVANTAGE HERE. Radiotherapy and some chemotherapy act partly through oxidative stress. For this reason MSK states plainly that CoQ10's antioxidant properties may REDUCE the effectiveness of chemotherapy and radiation therapy ^[1]. This is the same concern that applies to antioxidant supplements as a class.

INTERACTIONS WITH CANCER AND OTHER TREATMENT

• chemotherapy and radiotherapy — possible reduction in treatment effectiveness due to antioxidant activity ^[1];
• warfarin — CoQ10 may antagonise its anticoagulant effect ^[1];
• increased bleeding risk has also been reported ^[1].

SAFETY. Adverse effects are infrequent: nausea, diarrhoea and appetite suppression ^[1].

WHAT THIS MEANS

A product bought “to protect the heart” during chemotherapy may work against the treatment, and in breast cancer patients a higher hazard of recurrence was described with antioxidant supplementation. Any decision about supplementation during cancer treatment belongs to the treating physician, who knows the full medication list. This entry is not medical advice.

Sources

1. Memorial Sloan Kettering Cancer Center — About Herbs: Coenzyme Q10: mskcc.org ↗

WHERE THE DEFICIENCY COMES FROM

Niacin (vitamin B3) is obtained not only from food but also from tryptophan, an amino acid supplied with dietary protein. Neuroendocrine tumours causing carcinoid syndrome divert tryptophan elsewhere: they consume it to produce serotonin. When the tumour takes up a large share of the tryptophan pool, the substrate for niacin synthesis may run short - this is the mechanism of deficiency described in the European guidelines ^[1]. The extreme form of that deficiency is pellagra, classically described as a triad: skin lesions, diarrhoea and cognitive disturbance ^[1].

WHAT THE EVIDENCE SHOWS

A 2018 review of carcinoid syndrome brings together figures that are worth reading side by side, because they describe two different things. Full clinical pellagra is rare - "usually<1%, but up to 3% in one study" of patients ^[2]. When niacin was actually measured, however, deficiency proved far more common: in one study it affected 10 of 36 patients, that is 28% ^[2]. Among 42 supplemented patients, niacin levels normalised, and before supplementation urinary niacin metabolites were below normal in 45% of those tested ^[2].

Put differently: symptomatic pellagra is uncommon in this disease, but biochemical deficiency - invisible without testing - is frequent.

STRENGTH OF EVIDENCE

Limited. All the figures quoted come from small patient series and review articles, not from randomised controlled trials ^[2]. There is no study comparing supplementation with no supplementation in terms of survival, quality of life or complication rates. What is documented is that supplementation normalises niacin levels ^[2] - an effect on a laboratory measure, not on hard endpoints. The mechanism of tryptophan depletion, by contrast, is well described and consistently presented in society guidelines ^[1].

INTERACTIONS WITH CANCER TREATMENT

Two points matter in practice.

The first concerns somatostatin analogues, the mainstay of symptomatic treatment in carcinoid syndrome. The ENETS guidelines state that in patients previously treated with somatostatin analogues, deficiencies of fat-soluble vitamins should be looked for and adequately substituted ^[1]. Cancer treatment therefore changes nutritional status itself and can be a reason for monitoring, not merely a background factor.

The second concerns the form and dose of the vitamin. The literature describes nicotinamide at 250-500 mg per day orally for treating deficiency ^[3], whereas high doses of niacin (of the order of 3000 mg per day) may cause flushing, jaundice, impaired vision and abdominal discomfort, and sustained high doses may cause liver injury ^[3]. The tolerable upper intake level for adults is 35 mg per day ^[3]. In carcinoid syndrome this carries extra weight: flushing is the most prevalent symptom of the disease itself, reported in approximately 85% of patients ^[4]. A drug-induced symptom may therefore be mistaken for the disease or for its exacerbation - and vice versa. This is one reason why the choice of preparation and dose is not a neutral matter and belongs to the physician.

WHAT THIS ENTRY DOES NOT SAY

It does not say that every patient with a neuroendocrine tumour should take vitamin B3, nor what dose is appropriate in an individual case. The figures quoted describe groups of patients studied in the literature, not a recommendation for one person.

WHAT TO DISCUSS WITH THE TREATING TEAM

Whether, in a given situation, it is reasonable to check nutritional status and vitamin sufficiency - particularly during long-term somatostatin analogue treatment ^[1], chronic diarrhoea, or skin and cognitive symptoms that could correspond to the described triad ^[1]. Diagnosing a deficiency requires testing, and diagnostic and therapeutic decisions are made solely by a specialist physician.

WHY THIS ENTRY EXISTS

A low haemoglobin level is popularly equated with iron deficiency, and iron products are among the most commonly bought without prescription. In bone marrow disorders the mechanism differs: the marrow fails to produce normal cells even though the body is not short of iron.

WHAT THE SOURCE SAYS

In its summary on myelodysplastic syndromes NCI describes that anaemia is treated with red-cell transfusions to avoid symptoms, and that the oral iron-chelating agent deferasirox has come into widespread use. Chelation is the REMOVAL of iron from the body, used precisely because repeated transfusions accumulate it.

HOW STRONG IS THE EVIDENCE

NCI states explicitly that while some consensus panels advocate prophylactic iron chelation in patients with ongoing transfusion needs, the impact of chelation on survival and disease progression is unknown. The honest conclusion is therefore limited: iron accumulation itself is certain, the benefit of treating it is not.

WHAT THIS MEANS FOR THE READER

• A blood count is not enough to diagnose iron deficiency; iron studies, including ferritin, serve that purpose.
• Iron deficiency can coexist with cancer, for instance with gastrointestinal bleeding, and then iron treatment may be justified. This entry does not claim iron is always harmful; it says it must not be chosen on one's own.
• Multi-ingredient and "strengthening" preparations often contain iron, which is easy to overlook. It is worth showing the package to the physician.
• Supplementation, its dose and any chelation are decided by the haematologist in charge of treatment.

WHERE THE DEFICIT COMES FROM IN ONCOLOGY

Unlike most nutritional deficits, this one is usually not about what the patient eats. Mechanistic reviews describe it as drug-induced renal magnesium wasting, listing antineoplastic agents, diuretics, some antibiotics and proton pump inhibitors ^[3][4]. The practical consequence is that neither diet nor a tablet can close the tap through which magnesium escapes; losses can only be replaced for as long as their cause persists.

HOW OFTEN IT HAPPENS

In a multicentre study of 304 patients with RAS/RAF wild-type colorectal cancer treated with cetuximab, hypomagnesaemia was found in 29.9% and hypokalaemia in 20.7% ^[1]. A twenty-year pharmacovigilance analysis indicates that of the two anti-EGFR antibodies, panitumumab shows the stronger association with hypomagnesaemia ^[6]. With platinum agents the phenomenon has long been recognised; a case of profound hypomagnesaemia emerging a year after carboplatin has also been described, although this is a single case report, the weakest form of evidence ^[5].

WHAT HAS NOT BEEN CONFIRMED

A belief circulates online that low magnesium signals that the disease is progressing, or conversely that it heralds a good response to treatment. The study cited above tested this directly and found no significant association between hypomagnesaemia and either progression-free or overall survival ^[1]. The negative result is informative in its own right: the disturbance is treated because it has consequences of its own, not because it forecasts anything.

WHY THIS IS NOT A DECISION TO TAKE ALONE: In oncology magnesium is at times part of hospital treatment rather than a pharmacy purchase. In a prospective study of 207 patients with locally advanced head and neck cancer receiving high-dose cisplatin, intravenous magnesium was used as nephroprotection; acute kidney disease occurred in 5.3% of patients (11/207; 95% CI 2.7-9.3) ^[2]. Management reviews additionally list agents that reduce renal magnesium loss, such as amiloride and SGLT2 inhibitors ^[4]. Every one of these decisions — whether, when, in what form and under what laboratory monitoring — belongs to the physician directing the cancer treatment. This service does not interpret laboratory results and does not give doses.

INTERACTIONS AND CAUTIONS

• Proton pump inhibitors, very frequently taken during cancer treatment, lower magnesium in their own right and add to the effect of chemotherapy ^[3][4].
• The deficit may appear with delay, including after platinum treatment has ended, so previous chemotherapy is worth mentioning to any physician, including those outside oncology ^[5].
• Taking magnesium unsupervised may mask a problem whose origin lies in the kidneys and delay its recognition.

WHAT MAGNESIUM DOES NOT DO

None of the sources cited here shows that magnesium supplementation reduces the risk of developing cancer, slows its growth, or increases the effectiveness of anticancer treatment. The role described here concerns a complication of treatment, not the disease itself.

WHY THIS ENTRY EXISTS

Neuropathy after chemotherapy is one of those consequences of treatment for which medicine currently has least to offer — which is precisely why it is an area where patients most often reach for supplements on their own. Alpha-lipoic acid is among the most popular of them. This page describes what is known about it, not what anyone should do.

WHAT THE GUIDELINES SAY

• for the PREVENTION of chemotherapy-induced peripheral neuropathy, NO agent is recommended ^[1];
• the use of acetyl-L-carnitine for prevention of CIPN is explicitly discouraged ^[1];
• for TREATMENT of established painful neuropathy, duloxetine is the only agent with appropriate supporting evidence ^[1];
• alpha-lipoic acid is not among the recommended agents.

WHAT THE DATA ON ALA ITSELF SHOW

The MSKCC monograph records isolated reports suggesting ALA may be a useful adjunct in reducing paclitaxel-induced neuropathy, together with observations on doxorubicin cardiotoxicity and on salivary gland dysfunction and oral mucositis after radiotherapy ^[2]. These are results from small, single studies — not from registrational trials or reviews that would support a recommendation.

THE KEY WARNING — INTERACTION WITH CANCER TREATMENT: Alpha-lipoic acid may ANTAGONISE the effects of chemotherapy and radiotherapy because of its antioxidant properties ^[2]. This warning points in exactly the opposite direction from the hoped-for benefit, and it concerns the effectiveness of anticancer treatment rather than the patient's comfort. Deciding whether to use ALA during active treatment therefore requires assessment of the individual situation by the treating team and cannot be replaced by any general recommendation.

SEPARATELY — OTHER PRACTICALLY RELEVANT INTERACTIONS:

• ALA affects carbohydrate metabolism and may intensify the action of glucose-lowering drugs in people treated for diabetes;
• neuropathy in a cancer patient often has several causes at once (vitamin B12 deficiency, diabetes, alcohol, pressure from the tumour itself), so its assessment belongs to a physician — the symptom alone does not identify the cause.

WHAT THIS ENTRY DOES NOT SAY

We give no doses or dosing schedules, since that would be advice for an individual rather than a description of the state of knowledge. Nor do we claim that ALA does not work — we state that the evidence is limited and that alongside it stands a warning about possible weakening of treatment. Absence of high-quality evidence is not the same as evidence of absence, but during anticancer treatment the burden of that risk falls on the patient, not on the supplement.

THE DECISION BELONGS TO THE DOCTOR

Management of chemotherapy-induced neuropathy, and the taking of any supplements during cancer treatment, is decided by the treating specialist. All supplements being taken should be disclosed to the treating team — including those regarded as natural.

Sources

1. [1] Loprinzi CL i wsp. — Prevention and Management of Chemotherapy-Induced Peripheral Neuropathy in Survivors of Adult Cancers: ASCO Guideline Update. J Clin Oncol 2020 (PMID 32663120) — brak zalecanego środka w profilaktyce CIPN; acetylo-L-karnityna odradzana; duloksetyna jedynym lekiem z odpowiednimi dowodami w leczeniu bolesnej CIPN: europepmc.org ↗
2. [2] Memorial Sloan Kettering Cancer Center — About Herbs: Alpha-Lipoic Acid (pojedyncze doniesienia o zmniejszeniu neuropatii po paklitakselu; ostrzeżenie o możliwym antagonizowaniu chemioterapii i radioterapii): mskcc.org ↗

WHAT IT IS AND WHY IT IS DISCUSSED

L-carnitine is an amino-acid derivative whose role in the cell is to transport long-chain fatty acids across the inner mitochondrial membrane, enabling their beta-oxidation ^[1]. Because this is part of how the cell produces energy, carnitine is marketed for fatigue — including fatigue during cancer treatment — and also for heart disease, diabetic nerve pain, insulin resistance and male infertility ^[1]. The mechanism sounds persuasive; what follows is what human studies actually showed.

WHAT THE EVIDENCE SAYS

The evidence is inconsistent and its balance is negative.

• Current guidelines do NOT recommend L-carnitine for cancer-related fatigue ^[1].
• In a randomised, double-blind, placebo-controlled phase 3 ECOG trial, four weeks of L-carnitine at 2 g per day did not improve fatigue in patients with invasive malignancies and good performance status ^[2].
• A systematic review with meta-analysis concludes that carnitine supplementation is unlikely to give a clinically meaningful benefit for cancer-related fatigue in the chemotherapy-treated population ^[3].
• Individual small oncology studies described improved nutritional status in pancreatic cancer and reduced muscle spasms caused by vismodegib ^[1]. These are observations from small studies, on endpoints other than fatigue, and they do not offset the phase 3 result.

WARNING: THE DERIVATIVE ACETYL-L-CARNITINE AND NEUROPATHY. This is the most important practical item on this card, and it concerns not L-carnitine itself but its derivative. Acetyl-L-carnitine, studied to PREVENT chemotherapy-induced peripheral neuropathy, in fact INCREASED it, and guidelines do not recommend it for that purpose ^[1]. A supplement whose name sounds like nerve support can therefore worsen the very complication it was meant to prevent.

INTERACTIONS WITH TREATMENT, AND ADVERSE EFFECTS.

• Warfarin: L-carnitine may have additive anticoagulant effects with warfarin, increasing bleeding risk ^[1]. This matters often in oncology, because anticoagulation is standard care for cancer-associated thromboembolism.
• Neurotoxic chemotherapy (platinum agents, taxanes): acetyl-L-carnitine is not to be added for nerve protection — see the warning above ^[1].
• Adverse effects: dyspepsia and heartburn; also reported are flu-like syndrome, injection-site reaction, pain, pharyngitis, headache, diarrhoea and hypertension; high doses may cause an unpleasant body odour ^[1].

WHAT THIS CARD DOES NOT SAY

This is neither a recommendation nor a warning-off for any individual. Fatigue in cancer has many reversible causes — anaemia, hypothyroidism, pain, disturbed sleep, drug effects, malnutrition — and it is identifying those, not a supplement, that changes a patient's situation. Decisions about supplements taken during treatment belong to the treating physician, who knows the patient's full medication list.

Sources

1. [1] Memorial Sloan Kettering Cancer Center, About Herbs — Carnitine (mechanizm, deklarowane zastosowania, podsumowanie kliniczne, brak zalecenia w wytycznych, nasilenie neuropatii przez acetylo-L-karnitynę, interakcja z warfaryną, działania niepożądane): mskcc.org ↗
2. [2] Cruciani RA i wsp. L-carnitine supplementation for the management of fatigue in patients with cancer: an Eastern Cooperative Oncology Group phase III, randomized, double-blind, placebo-controlled trial. PMID 22987089: pubmed.ncbi.nlm.nih.gov ↗
3. [3] Efficacy and effectiveness of carnitine supplementation for cancer-related fatigue: a systematic literature review and meta-analysis (PMC5707696): pmc.ncbi.nlm.nih.gov ↗

WHAT IT IS AND WHY PATIENTS TAKE IT

Ashwagandha (Withania somnifera) is an Ayurvedic herb sold over the counter as a dietary supplement. Cancer patients most often take it on their own hoping to reduce anxiety, stress and fatigue, improve sleep and — less commonly — ease joint pain.

WHAT THE EVIDENCE SHOWS

Clinical data are limited and come from few, small studies. Memorial Sloan Kettering notes reports of reduced chemotherapy-induced fatigue in breast cancer patients, and of improved sleep quality and reduced anxiety. This is not a basis for a recommendation: there are no large randomised trials, no independent confirmation, and the endpoints are subjective.

WHAT ASHWAGANDHA DOES NOT DO

Laboratory studies have shown slowed growth of cancer cells, but — as MSKCC states explicitly — this effect has not been observed in humans. Ashwagandha is not anticancer treatment and does not replace any therapy.

SAFETY — THIS IS THE MAIN ISSUE. Commonly reported adverse effects are drowsiness, nausea, headache, stomach upset and diarrhoea. Serious events have also been reported:

• liver injury associated with use of ashwagandha supplements,
• thyrotoxicosis,
• kidney transplant rejection.

SPECIFIC WARNINGS

• Pregnancy: do not use — the herb may increase the risk of miscarriage.
• Hormone-sensitive prostate cancer: discuss with the treating physician, because ashwagandha may raise testosterone levels.
• Autoimmune disease: the herb may trigger or exacerbate it.
• Liver disease or abnormal liver tests: discuss with the treating physician before considering use.

INTERACTIONS WITH CANCER TREATMENT

• CYP3A4: ashwagandha is a moderate inducer of this enzyme. Many oncology drugs (including kinase inhibitors) are metabolised by it, and induction may lower their blood levels.
• CYP2B6: inhibition shown in vitro.
• Sedatives and antiepileptics (benzodiazepines, barbiturates): ashwagandha has sedative, GABAergic properties; additive effects are possible.
• Thyroid medication: thyroxine levels may rise.
• Digoxin: may cause falsely elevated immunoassay results.

MSKCC notes that the clinical relevance of several of these interactions is yet to be determined — which means they have not been measured, not that they are unimportant.

BOTTOM LINE

The quality of evidence for benefit is limited, while the list of documented hazards — including liver injury and CYP3A4 induction — is concrete. Any supplement use during cancer treatment is a decision for the treating physician, who knows the patient's full medication list.

WHAT IT IS AND WHY PATIENTS TAKE IT

Berberine is an alkaloid found in several medicinal plants (including barberry and goldenseal). It is sold as a dietary supplement. Patients most often take it for reasons unrelated to cancer: type 2 diabetes, raised cholesterol, digestive complaints, and under the banner of "cleansing".

WHAT THE EVIDENCE SHOWS

Memorial Sloan Kettering summarises that several studies and meta-analyses suggest benefit from berberine, but better-designed studies are needed and the effect may be small. Diabetes studies are described as of limited quality. In hyperlipidaemia, improvement in the lipid profile has been reported in people who cannot or will not take statins.

THE ONE ONCOLOGY FINDING

A reduced rate of recurrence of colorectal adenomas has been reported in people after adenoma removal. This is prevention of recurrence of BENIGN lesions with malignant potential, not treatment of colorectal cancer — and it should be read that way. There are no data showing that berberine treats any malignancy.

ADVERSE EFFECTS

Reported as mild: appetite loss, upset stomach, diarrhoea, constipation, rash.

SPECIFIC WARNINGS

• Pregnancy and breastfeeding: do not use — berberine may worsen neonatal jaundice.
• Bosutinib: do not use together (see interactions).
• Immunosuppressants (tacrolimus, ciclosporin): avoid.

INTERACTIONS WITH CANCER AND SUPPORTIVE TREATMENT

• CYP2D6, CYP2C9, CYP3A4: berberine reduces the activity of these enzymes, which can alter levels of many drugs cleared by them — in oncology this includes kinase inhibitors.
• Bosutinib: simulations predict a 1.3-fold increase in drug exposure; MSKCC advises against combining them.
• Tacrolimus and ciclosporin: berberine raises their blood levels — relevant after transplantation and in graft-versus-host disease.
• Sulfonylureas: additive blood-glucose-lowering effect is possible.

BOTTOM LINE

Berberine is not anticancer therapy and there is no basis for treating it as an adjunct to cancer treatment. It does, however, have a concrete documented interaction profile that can change the levels of drugs a patient is already taking. Any supplement use during cancer treatment is a decision for the treating physician, who knows the patient's full medication list.

WHY PATIENTS REACH FOR IT

Echinacea is among the most widely bought herbal products, marketed for colds, flu, wound healing and "immune support" ^[1]. In oncology it is taken mainly by people whose white cell counts have been lowered by chemotherapy — precisely the situation in which the promise of "boosting the immune system" sounds most convincing. That intuition, rather than the herb itself, is the problem here.

WHAT THE EFFICACY TRIALS SHOWED

The evidence is mixed and limited. Memorial Sloan Kettering Cancer Center reports that echinacea was INEFFECTIVE in preventing the common cold caused by rhinoviruses ^[1]. On the other hand, one influenza trial found it as effective as oseltamivir, with fewer adverse events ^[1]. Neither line of evidence concerns cancer patients, and neither shows that the supplement repairs immunity damaged by chemotherapy — no such evidence exists.

WHY THIS IS NOT A NEUTRAL SUPPLEMENT IN ONCOLOGY.

• Some studies suggest echinacea could decrease plasma drug levels, affect therapeutic efficacy, or cause adverse effects with some anticancer drugs ^[1].
• Profound thrombocytopenia was reported in a lung cancer patient receiving cisplatin and etoposide, attributed to echinacea use ^[1].
• In laboratory studies echinacea inhibits CYP3A4 and CYP2C8 ^[1]. The thrombocytopenia seen with etoposide was thought likely to be due to CYP3A4 inhibition ^[1].
• The same mechanism works in the opposite direction: in vitro there is a risk of subtherapeutic systemic exposure of prodrugs such as tamoxifen, which must be metabolised to become active ^[1].
• Echinacea may antagonise the effects of immunosuppressants ^[1].

ADVERSE EFFECTS

Reported effects include headache, dizziness, nausea, constipation, gastrointestinal upset and rash ^[1]. More rarely: thrombotic thrombocytopenic purpura, acute hepatitis, acute liver failure, leukopenia and exacerbation of pemphigus vulgaris ^[1].

CONTRAINDICATIONS. Memorial Sloan Kettering lists: chemotherapy, autoimmune and allergic conditions, immunosuppression, and pregnancy or breastfeeding ^[1]. Note the apparent contradiction that is in fact consistent: a product said to stimulate the immune response is unsuitable both when the immune system attacks the body's own tissues and when it is being deliberately suppressed by drugs.

STRENGTH OF EVIDENCE

Limited. The efficacy trials concern respiratory infections in generally healthy people, give conflicting results, and do not transfer to a patient undergoing cancer treatment. The harm evidence rests on case reports and laboratory work on drug metabolism ^[1] — it does not allow the frequency of complications to be estimated, but it does establish that they are possible and involve drugs used in everyday oncology practice.

WHAT THIS ENTRY DOES NOT SAY

It neither recommends nor advises against anything for any individual, and gives no doses. It states what the trials showed and which interactions are documented. The decision to take or stop any supplement during chemotherapy belongs to the treating physician, who knows the full list of medicines taken.

SOURCES.

• ^[1] Memorial Sloan Kettering Cancer Center, About Herbs: Echinacea

Sources

1. [1] Memorial Sloan Kettering Cancer Center — About Herbs: Echinacea: mskcc.org ↗

WHY PATIENTS REACH FOR ALOE

Aloe gel is among the most common home remedies applied to the skin during radiotherapy — it is cheap, available without prescription and associated with soothing burns. Radiation dermatitis affects a large proportion of irradiated patients, and the expectation that a "burn" preparation will help here too is intuitive. Clinical evidence does not clearly bear that intuition out.

WHAT THE BREAST CANCER TRIAL SHOWED

A three-arm randomised phase III trial enrolled 248 patients with breast cancer assigned to powder, aloe cream or placebo cream; acute skin toxicity was scored weekly on a modified 10-point Catterall scale and patients rated their own symptom severity ^[1]. The aloe formulation did NOT reduce acute skin toxicity or symptom severity ^[1]. The authors found no evidence supporting prophylactic use of aloe and stated that their results support a dry powder skin care regimen ^[1]. They also noted that both study creams were associated with a greater skin reaction than the dry powder regimen ^[1].

WHAT THE HEAD AND NECK TRIAL SHOWED

A multicentre, randomised, double-blind, placebo-controlled trial enrolled 120 patients with head and neck cancer receiving concurrent chemoradiation; skin reaction was assessed with the RISRAS scale ^[2]. In the main comparison, median RISRAS values from week 1 to week 8 did NOT differ significantly between groups ^[2]. Differences appeared in individual weeks: moderate to severe erythema occurred in week 5 in 13.6% of patients using aloe versus 27.8% on placebo (p=0.05), and in week 6 in 24.1% versus 42.6% (p=0.038) ^[2].

HOW TO READ THE TWO TOGETHER

The two randomised trials give an inconsistent picture, and in both the main comparison showed no significant difference. A favourable result in individual weeks of follow-up is weaker ground than a result in the planned comparison across the treatment period. The honest conclusion is therefore: there is no high-quality evidence that aloe gel prevents radiation dermatitis or reduces its severity. This is not evidence that the gel is harmful on the skin — it is an absence of confirmed benefit.

ORAL MUCOSITIS

Preliminary findings suggest a benefit of aloe in preventing chemotherapy-induced oral mucositis in adults, and studies in children report a similar benefit ^[3]. These are preliminary data, not established practice.

THE KEY WARNING — GEL IS NOT JUICE: Aloe gel must not be confused with aloe juice or aloe latex; both contain anthraquinone, a cathartic laxative ^[3]. Internal use of aloe should be discouraged because of possible adverse effects ^[3]. Reported effects include stomach pain, nausea, vomiting, seizures, low potassium and liver dysfunction ^[3]. Low potassium matters particularly in cancer patients, who often receive drugs affecting electrolyte balance.

INTERACTIONS WITH CANCER TREATMENT

• liver enzymes: aloe juice inhibited CYP3A4 and CYP2D6, which may affect intracellular concentrations of drugs metabolised by these enzymes ^[3] — this concerns many anticancer drugs;
• surgery: excessive intraoperative bleeding was reported in a patient taking oral aloe vera tablets, under sevoflurane anaesthesia ^[3];
• practical conclusion: information about taking aloe orally should reach the treating team before a planned procedure and when systemic treatment is being decided. The decision rests with the treating physician.

Sources

1. [1] Hoopfer D i wsp., Three-Arm Randomized Phase III Trial: Quality Aloe and Placebo Cream Versus Powder as Skin Treatment During Breast Cancer Radiation Therapy, Clin Breast Cancer 2015: pubmed.ncbi.nlm.nih.gov ↗
2. [2] Reduction in severity of radiation-induced dermatitis in head and neck cancer patients treated with topical aloe vera gel: a randomized multicenter double-blind placebo-controlled trial, Eur J Oncol Nurs 2022: pubmed.ncbi.nlm.nih.gov ↗
3. [3] Memorial Sloan Kettering Cancer Center, About Herbs: Aloe Vera (zapalenie blony sluzowej, ostrzezenia, interakcje): mskcc.org ↗

WHAT IT IS

EGCG (epigallocatechin gallate) is the principal polyphenol of green tea. Two things that are often conflated must be kept apart: an infusion of green tea leaves, and a supplement containing an extract in which the EGCG dose is many times higher. The safety concerns described below apply to extracts, not to tea drunk in ordinary amounts ^[4].

THE MOST IMPORTANT WARNING — BORTEZOMIB (MULTIPLE MYELOMA). Bortezomib carries a boronic acid group. EGCG forms a stable chemical adduct with it, so the drug no longer binds the proteasome — that is, it stops doing what it is given for. In myeloma and glioma cell lines the antitumour effect of bortezomib was blocked, and in a mouse model it was abolished completely ^[2]. The NCI PDQ database describes this mechanism explicitly and notes that human studies have not been performed ^[3]. Memorial Sloan Kettering lists the interaction among its patient warnings ^[4].

• Level of evidence: laboratory and animal studies plus a defined chemical mechanism — there are no clinical data.
• Why it is nevertheless taken seriously: the mechanism is direct and requires no assumption beyond the chemistry of the two molecules.

OTHER DOCUMENTED INTERACTIONS

• Irinotecan — in models, higher plasma drug levels and reduced biliary excretion of the active metabolite SN-38, meaning a risk of increased toxicity ^[4].
• Kinase inhibitors (erlotinib, lapatinib, sunitinib, palbociclib) — reduced oral bioavailability in animal models; a single human case has been reported with sunitinib ^[4].
• Statins — increased exposure to atorvastatin and a marked decrease in exposure to rosuvastatin ^[4].
• Nadolol — the extract inhibits the OATP1A2 transporter and reduces drug absorption ^[4].

WHAT HUMAN STUDIES HAVE NOT SHOWN

• Prostate cancer: a double-blind randomised trial in 97 men with precancerous lesions (HGPIN/ASAP), 400 mg EGCG daily for one year. Cancer was diagnosed in 5 of 49 men on the preparation and 9 of 48 on placebo; p=0.25. The primary endpoint was not met ^[1].
• Oral precancerous lesions: a randomised phase 2 trial showed a clinical response in 50% (n=28) versus 18.2% on placebo (n=11), p=0.09 — not statistically significant ^[6].
• Chronic lymphocytic leukaemia: a single-arm phase 2 study (n=42) reported a response in 69% of patients, but measured by a surrogate marker (fall in lymphocyte count, reduction of nodal masses), not by survival or time to treatment ^[7].
• Neither the NCI nor Memorial Sloan Kettering recommends green tea or EGCG for cancer prevention or treatment; the FDA has approved no such indication ^[8].

SAFETY OF EXTRACTS

The European Food Safety Authority concluded that catechins from a traditional infusion are generally safe, whereas doses from supplements of 800 mg EGCG per day and above produced a statistically significant rise in transaminase activity; the panel was unable to identify a safe dose for extracts ^[5]. The NIH LiverTox registry assigns green tea extracts its highest likelihood category for liver injury, describing more than a hundred cases including acute liver failure requiring transplantation; the injury is idiosyncratic and typically appears after one to six months of use ^[9].

WHAT TO DISCUSS WITH THE TREATING PHYSICIAN

Every supplement being taken — and particularly so during treatment with bortezomib, irinotecan or a kinase inhibitor. The decision to stop or continue a preparation rests with the specialist who knows the patient's full medication list; this page describes the state of knowledge, not a recommendation for any individual.

Sources

1. [1] Kumar NB i wsp. Randomized, placebo-controlled trial of green tea catechins for prostate cancer prevention. Cancer Prev Res 2015: pmc.ncbi.nlm.nih.gov ↗
2. [2] Golden EB i wsp. Green tea polyphenols block the anticancer effects of bortezomib. Blood 2009;113(23):5927-37: pubmed.ncbi.nlm.nih.gov ↗
3. [3] NCI PDQ — Cancer Therapy Interactions With Foods and Dietary Supplements (Health Professional Version): cancer.gov ↗
4. [4] Memorial Sloan Kettering Cancer Center — About Herbs: Green Tea: mskcc.org ↗
5. [5] EFSA — Scientific opinion on the safety of green tea catechins (2018): efsa.europa.eu ↗
6. [6] Tsao AS i wsp. Phase II randomized trial of green tea extract in oral premalignant lesions. Cancer Prev Res 2009: pubmed.ncbi.nlm.nih.gov ↗
7. [7] Shanafelt TD i wsp. Phase 2 trial of daily oral Polyphenon E in patients with CLL. Cancer 2013: pubmed.ncbi.nlm.nih.gov ↗
8. [8] NCI PDQ — Prostate Cancer, Nutrition, and Dietary Supplements (Patient Version): cancer.gov ↗
9. [9] NIH LiverTox — Green Tea (Camellia sinensis): ncbi.nlm.nih.gov ↗

WHAT IS BEING STUDIED

Zinc is a trace element required for epithelial healing and normal taste perception. In cancer patients it has been tested in two settings, both linked to radiation of the head and neck region:

• oral mucositis during radiotherapy and chemoradiotherapy,
• radiation-induced taste disturbance (dysgeusia).

WHAT THE EVIDENCE SAYS

The NCI PDQ guidance on oral complications lists “oral zinc supplements in oral cancer patients receiving radiation therapy or chemoradiation”, but assigns it Level of Evidence IV — the lowest rating in that scale, based on expert opinion and observation rather than high-quality trials ^[1].

MSKCC summarises the literature more cautiously and points to a discrepancy that matters in practice: reduced mucositis was reported in some patients receiving radiation or chemotherapy, but NOT in head and neck cancer patients — the very group in which the problem is most common. For taste, results are mixed; a meta-analysis suggests zinc may reduce the INCIDENCE of radiation-induced dysgeusia while having minimal effect on symptoms already present ^[2].

WHO IT APPLIES TO

There is no basis for treating zinc as cancer therapy — none of the referential sources attributes an antitumour effect to it. It is considered only as supportive care for mucosal and taste complications, and the decision to supplement, at what dose and for how long, belongs to the treating physician who knows the patient's other treatment.

ADVERSE EFFECTS AND CAUTIONS

Zinc lozenges cause taste disturbances, nausea, vomiting, upset stomach and diarrhoea. Doses of 100–300 mg per day lead to copper deficiency, depressed immune function, headache, chills, fever and fatigue ^[2] — so the very symptom the supplement is meant to prevent can result from taking too much of it.

INTERACTIONS WITH CANCER TREATMENT

This is the most important part of this entry:

• zinc reduces the availability of fluoroquinolone and tetracycline ANTIBIOTICS; if a physician recommends supplementation, it should be taken 2 hours before or 4 hours after the antibiotic ^[2]. In neutropenic patients, for whom antibiotics can be life-saving, this matters directly;
• the immune suppression seen with chronic zinc excess is particularly unwelcome during myelosuppressive chemotherapy;
• zinc-induced copper deficiency may compound treatment-related anaemia and obscure its cause.

WHAT WE DO NOT KNOW

There is no agreement on dose, timing or duration of supplementation, and it is unclear whether any benefit exists in head and neck cancer at all. “No high-quality evidence” is an honest summary of the current state of knowledge.

Sources

1. NCI PDQ — Oral Complications of Chemotherapy and Head/Neck Radiation (Health Professional Version): cancer.gov ↗
2. Memorial Sloan Kettering Cancer Center — About Herbs: Zinc: mskcc.org ↗

WHAT THE EVIDENCE SAYS The broadest appraisal is a 2025 systematic review (European Journal of Clinical Pharmacology) covering 34 randomised trials and 2,580 patients undergoing cancer treatment ^[1]. Patients most often had head and neck cancers, followed by breast, prostate and colorectal cancer; curcumin was given topically or systemically ^[1]. Results for oral and skin symptoms, pain, body weight, body composition, survival and disease progression were heterogeneous ^[1]. The authors recorded significant findings only for oral mucositis and weight loss ^[1].

STRENGTH OF EVIDENCE — WEAK The authors state plainly that all included studies had a moderate to high risk of bias, and that because of heterogeneous results and methodological limitations no clear statement about the effectiveness of curcumin in cancer patients can be made ^[1]. Higher-quality research is needed ^[1]. A harm was also recorded: in one trial vomiting was significantly more frequent in the curcumin group ^[1].

INTERACTIONS WITH CANCER TREATMENT This is the most important part of this entry. In a 2019 study (Cancers), in breast cancer patients taking tamoxifen, adding curcumin (1,200 mg three times daily) reduced the area under the curve for endoxifen by 7.7% (95% CI: −15.4 to 0.7%; p=0.07), and curcumin with piperine by 12.4% (95% CI: −21.9 to −1.9%; p=0.02) ^[2]. Endoxifen is the active metabolite of tamoxifen — the form of the drug that does the work ^[2]. The authors conclude that co-treatment with curcumin could lower endoxifen concentrations below the threshold for efficacy, in their estimate potentially in 20–40% of patients, especially in extensive CYP2D6 metabolisers ^[2]. Note that piperine, added to supplements precisely to improve curcumin absorption, made the unfavourable effect LARGER in this study ^[2].

The National Cancer Institute states the general rule: “Tell your doctor if you're taking any dietary supplements, even vitamins, no matter how safe you think they are”, noting that some such products can change how cancer treatment works ^[3].

THE SCOPE OF WHAT WE WRITE HERE We give no figures for interactions between curcumin and cytotoxic drugs or kinase inhibitors, because we could not confirm them in accessible reference-class sources — the only clinically confirmed interaction in patients is the tamoxifen interaction described above. We also found no clinical data on perioperative bleeding risk in cancer patients taking curcumin. A missing number here is information, not an oversight: an unverified number would be worse than none.

This page describes the state of knowledge. It is not advice for any individual and not a recommendation to take or stop any preparation.

Sources

1. Gutsche et al. — Curcumin as a complementary treatment in oncological therapy: a systematic review, European Journal of Clinical Pharmacology 2025: europepmc.org ↗
2. Hussaarts et al. — Impact of Curcumin (with or without Piperine) on the Pharmacokinetics of Tamoxifen, Cancers 2019: europepmc.org ↗
3. National Cancer Institute — Complementary and Alternative Medicine (CAM): cancer.gov ↗