Cancer prevention through supplements
The idea that antioxidants (beta-carotene, vitamins E, C, selenium) in healthy people or risk groups reduce cancer incidence. The CARET (NEJM 1996) and ATBC (NEJM 1994) trials showed the opposite: in smokers beta-carotene INCREASED lung cancer incidence. The 2012 Cochrane review of antioxidants found no reduction in all-cause mortality and recorded increased mortality for beta-carotene.
10 drugs
Also known as: Antioxidant supplements for cancer, Vitamins for cancer prevention
Drugs used for this condition
Marketing claims without evidence base
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
- DBeta-1,3/1,6-D-glucan (yeast or oat)Not recommended · Polysaccharide immunomodulator. Oat beta-glucan is a dietary fibre with EFSA-approved cholesterol health claim. Yeast beta-glucan (Wellmune) is a supplement with immunity marketing without EFSA approvalBeta-1,3/1,6-D-glucan is a polysaccharide from yeast cell walls or from oats, sold as an immune supplement and marketed for cancer prevention. There is no solid evidence for this use: the available data do not show that taking this supplement lowers cancer risk. What actually reduces that risk are other measures – not smoking, limiting alcohol, keeping a healthy weight, HPV and hepatitis B vaccination, and age-appropriate screening. This supplement should not replace approaches with proven benefit, or you may miss the care or testing you actually need.
- DEpigallocatechin-3-gallate (EGCG, main green tea polyphenol)Not recommended · Catechin polyphenol from green tea (Camellia sinensis), supplement. EFSA 2018 limited safe dose from supplements to 800 mg/day due to hepatotoxicityEGCG is actively sold as a «natural oncoprotector» based on laboratory tumour cell proliferation inhibition data. Filippini 2020 Cochrane review included 142 studies on green tea and cancer prevention: data inconsistent; for breast, prostate, stomach and lung cancer – inconclusive evidence; no evidence base to recommend EGCG supplements for cancer incidence reduction. USPSTF 2022 recommends against routine vitamin-mineral supplement use for cancer prevention (D recommendation). EFSA 2018 warned about EGCG hepatotoxicity risk at >800 mg/day – such doses are common precisely in «concentrated» supplements marketed as oncoprotectors. If EGCG was recommended for «cancer prevention» or adjuvantly with an oncological diagnosis, consider seeking a second opinion from an oncologist.
- DFisetin (flavonol from strawberries, mangoes and onions)Not recommended · Plant flavonol, supplement. Natural polyphenol from strawberries, mangoes, onions, apples. The biohacking industry positions it as a «senolytic» – an agent that clears senescent cellsFisetin is sold as a «natural oncoprotector» via laboratory pro-apoptotic data on tumour cells. No RCTs with cancer incidence or mortality endpoints in humans. USPSTF 2022 recommends against routine vitamin-mineral supplement use for cancer prevention (D recommendation). ESMO 2020 lists smoking cessation, weight normalisation, physical activity, alcohol restriction, UV protection, HPV and HBV vaccination, age-appropriate screening as primary prevention. If fisetin was recommended as «cancer prevention», consider seeking a second opinion from an oncologist.
- DOlive leaf extract (Olea europaea, oleuropein)Not recommended · Plant antioxidant, supplement. In EU – traditional herbal medicinal product (EMA HMPC monograph 2014)Olive leaf extract (Olea europaea) with oleuropein is sold as a supplement for cancer prevention. There is no convincing evidence of benefit for this use – the data needed to show that such supplements lower cancer risk simply are not there. What does lower risk are approaches with proven benefit: quitting smoking, age- and risk-appropriate screening, and vaccination against HPV and hepatitis B. Do not use this extract in place of prevention or treatment with proven benefit, since that can mean missing the care you need.
- DPycnogenol (French maritime pine bark extract, Pinus pinaster)Not recommended · Plant polyphenol complex, supplement. Standardised maritime pine bark extract with 65–75% oligomeric proanthocyanidinsPycnogenol is sold for «cancer prevention» via antioxidant action. No evidence base for cancer incidence or mortality reduction in humans. USPSTF 2022 reviewed 84 studies on vitamin-mineral supplements and cancer prevention: recommendation against routine use for cancer prevention (D recommendation, no power). ESMO 2020 lists smoking cessation, weight normalisation, physical activity, alcohol restriction, UV protection, HPV and HBV vaccination, screening (colorectal, cervical, breast by age) as primary prevention. If pycnogenol was recommended as «cancer prevention» instead of proven measures, consider seeking a second opinion from an oncologist.
- DSulforaphane (isothiocyanate from broccoli sprouts)Not recommended · Plant isothiocyanate, supplement. Formed from glucoraphanin (Brassica oleracea) by myrosinase. Activator of the Nrf2-Keap1 pathwaySulforaphane is actively sold as a «natural oncoprotector» via activation of Nrf2-dependent phase II detoxification enzymes. Epidemiology shows that regular intake of cruciferous vegetables (broccoli, cauliflower, kale) is associated with reduced lung, gastric and colon cancer risk. But – from vegetables, not from isolated supplements. No RCTs with cancer incidence or mortality endpoints in humans with isolated sulforaphane. Memorial Sloan Kettering 2024 monograph notes «promising preclinical data, no clinical efficacy data». USPSTF 2022 recommends against routine vitamin-mineral supplement use for cancer prevention. If sulforaphane was recommended for «cancer prevention» instead of proven measures (smoking cessation, weight normalisation, screening), consider seeking a second opinion from an oncologist.
- FBeta-caroteneNot recommended · Provitamin A (plant precursor of retinol)Beta-carotene was marketed for decades as a «natural antioxidant» for cancer prevention. The ATBC trial (Finland, 1994, NEJM) in 29 133 smokers: beta-carotene 20 mg/day raised lung cancer incidence by 18% vs placebo. The CARET trial (USA, 1996, NEJM) in 18 314 smokers and asbestos workers was stopped early due to 28% higher lung cancer incidence and 17% higher all-cause mortality. Cochrane 2012 on antioxidants confirmed: beta-carotene increases all-cause mortality in non-deficient people. ESC 2021 and SEA do not recommend antioxidant complexes for prevention. In smokers and former smokers beta-carotene >5 mg/day is contraindicated. If beta-carotene was recommended «for cancer prevention», consider seeking a second opinion.
- FChaga (Inonotus obliquus)Not recommended · Medicinal mushroom parasitising birch. In Russia OTC «Befungin» registered, in the West – supplement. AEMPS does not register as medicineChaga is the top-selling «anti-tumour» mushroom in Russia and the West, promising prevention and treatment of malignancies. In Russia Befungin is registered as OTC «for gastritis and peptic ulcer, as symptomatic therapy in cancer» without confirmed antitumour efficacy. No quality international RCTs with tumour response or overall survival endpoints. MSKCC monograph 2023 classifies the evidence base as insufficient. Main risk – oxalate nephropathy: acute renal failure cases with high-dose chaga reported. If chaga was recommended for cancer as substitute for standard therapy (surgery, chemotherapy, radiotherapy, immunotherapy), consider seeking a second opinion from an oncologist.
- FReishi (Ganoderma lucidum, lingzhi)Not recommended · Medicinal mushroom of traditional Chinese medicine, supplement. AEMPS does not register as medicineReishi is sold as a «natural anti-cancer product» promising prevention and treatment of malignancies. Cochrane 2016 (Jin) reviewed 5 RCTs in 373 cancer patients: reishi as monotherapy showed no clinically meaningful tumour response. As chemotherapy adjunct it may improve quality of life and immune response; authors recommend «not as first-line or substitute for standard treatment». MSKCC monograph 2023 notes lack of convincing RCTs in cancer. If reishi was recommended for cancer as a substitute for standard therapy (surgery, chemotherapy, radiotherapy, immunotherapy) or for «recurrence prevention», consider seeking a second opinion from an oncologist.
How to read tiers A–F
Evidence tiers belong to the drug-indication pair, not to the drug as a whole: the same substance can be A for one condition and F for another.
- AStrong evidence – first or second line in international guidelines
- BRecommended in selected cases
- CStudy data contradict each other
- DBenefit not proven, no documented harm
- FDocumented harm, or risk without benefit