{"entity":{"id":"vitamin-a-supplements","kind":"technology","name":"Vitamin A supplements","aka":["Retinol supplements","Retinyl palmitate"],"tldr":"Vitamin A from food matters, but supplements have not prevented lung cancer or lengthened survival in melanoma, and some studies link them to a higher risk of prostate cancer. Because it is stored in the body, high doses taken for months can damage the liver, and it must be avoided in pregnancy.","summary":"Memorial Sloan Kettering's About Herbs entry on vitamin A summarises the cancer evidence plainly: supplementation does not protect against non-small cell lung cancer or prolong survival in melanoma, and may raise the risk of prostate cancer, so the advice is to obtain vitamin A from food. Vitamin A is fat-soluble and accumulates. MSK describes chronic toxicity usually with intakes above 30,000 IU a day, with significant liver injury reported at doses as low as 20,000 IU and in regular drinkers; symptoms include nausea, headache, blurred vision and raised liver enzymes. Supplements are contraindicated in pregnancy because of the risk to the baby. Interactions listed by MSK: large doses may increase the effect of warfarin, and taking vitamin A with prescribed retinoids such as tretinoin, acitretin or bexarotene adds to their side effects. Prescribed retinoids used in oncology (all-trans retinoic acid in acute promyelocytic leukaemia, bexarotene in skin lymphoma) are drugs given under supervision and are a different matter from over-the-counter vitamin A.","status":"phase-2","asOf":"2026-11-04","links":[{"label":"MSK About Herbs: Vitamin A (page last updated 21 August 2023)","url":"https://www.mskcc.org/cancer-care/integrative-medicine/herbs/vitamin"}],"tags":["complementary","supportive-care","evidence:harm"],"related":["beta-carotene-supplements","vitamin-e-supplements"],"cancers":[],"sections":["supportive-care","nutrition-lifestyle","prevention"],"technologies":["integrative-oncology","dietary-supplements-treatment-interactions"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["unproven-diet-claims"],"trials":[],"people":[],"bottlenecks":["b-misinformation","b-toxicity-qol"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"principle":"Retinoic acid, the active metabolite, acts through nuclear retinoic acid and retinoid X receptors to drive cell differentiation, which is why prescribed retinoids work in some cancers; excess retinol is stored in the liver, where it becomes toxic.","strengths":["Deficiency is real and worth correcting through diet","Clear guidance from MSK: food rather than supplements"],"limitations":["Supplements did not prevent lung cancer or extend melanoma survival","Liver toxicity with long-term high doses","Contraindicated in pregnancy; adds to the toxicity of prescribed retinoids"]},"route":"/technologies/vitamin-a-supplements/","neighbours":{"technology":[{"id":"beta-carotene-supplements","kind":"technology","name":"Beta-carotene supplements","route":"/technologies/beta-carotene-supplements/"},{"id":"dietary-supplements-treatment-interactions","kind":"technology","name":"Dietary supplements during cancer treatment: interactions and harms","route":"/technologies/dietary-supplements-treatment-interactions/"},{"id":"integrative-oncology","kind":"technology","name":"Evidence-based integrative oncology","route":"/technologies/integrative-oncology/"},{"id":"vitamin-e-supplements","kind":"technology","name":"Vitamin E supplements","route":"/technologies/vitamin-e-supplements/"}],"section":[{"id":"nutrition-lifestyle","kind":"section","name":"Diet, Exercise & Lifestyle","route":"/fronts/nutrition-lifestyle/"},{"id":"prevention","kind":"section","name":"Prevention & Risk","route":"/fronts/prevention/"},{"id":"supportive-care","kind":"section","name":"Supportive Care & Survivorship","route":"/fronts/supportive-care/"}],"term":[{"id":"unproven-diet-claims","kind":"term","name":"Unproven diet claims (alkaline, juice, 'anti-cancer' diets)","route":"/terms/unproven-diet-claims/"}],"bottleneck":[{"id":"b-misinformation","kind":"bottleneck","name":"Misinformation and unproven therapies","route":"/bottlenecks/b-misinformation/"},{"id":"b-toxicity-qol","kind":"bottleneck","name":"Toxicity and quality of life are undervalued","route":"/bottlenecks/b-toxicity-qol/"}]}}