# Vitamin A supplements

Source: https://onco.cc/technologies/vitamin-a-supplements/  
OnCo record `vitamin-a-supplements` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

## Fields

- Kind: Technology
- Status: phase-2
- Last checked: 2026-11-04
- Also known as: Retinol supplements; Retinyl palmitate
- Tags: complementary; supportive-care; evidence:harm
- 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

## Sources

- MSK About Herbs: Vitamin A (page last updated 21 August 2023): https://www.mskcc.org/cancer-care/integrative-medicine/herbs/vitamin

## Connected records

- technologies: [Beta-carotene supplements](https://onco.cc/technologies/beta-carotene-supplements/), [Dietary supplements during cancer treatment: interactions and harms](https://onco.cc/technologies/dietary-supplements-treatment-interactions/), [Evidence-based integrative oncology](https://onco.cc/technologies/integrative-oncology/), [Vitamin E supplements](https://onco.cc/technologies/vitamin-e-supplements/)
- fronts: [Diet, Exercise & Lifestyle](https://onco.cc/fronts/nutrition-lifestyle/), [Prevention & Risk](https://onco.cc/fronts/prevention/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- terms: [Unproven diet claims (alkaline, juice, 'anti-cancer' diets)](https://onco.cc/terms/unproven-diet-claims/)
- bottlenecks: [Misinformation and unproven therapies](https://onco.cc/bottlenecks/b-misinformation/), [Toxicity and quality of life are undervalued](https://onco.cc/bottlenecks/b-toxicity-qol/)

---
JSON: https://onco.cc/api/v1/entities/vitamin-a-supplements.json