Vitamin A

What it is

A fat-soluble vitamin (retinol and its esters from liver, dairy, eggs and fortified foods) that the body also makes from plant carotenoids. Prescription retinoids such as isotretinoin and acitretin are vitamin A derivatives and are reported to cause shedding in some people. A small 3-month study of isotretinoin 0.5 mg/kg/day found no significant change in measured hair parameters, so the effect depends on dose and person. Islamoglu 2019 Reviews of telogen effluvium list retinoids and excess vitamin A among common drug triggers. Hughes 2024

How it works

Retinoic acid signalling is part of the normal hair cycle, but excess appears to hold follicles in rest. In mice fed excess retinyl esters, more follicles were stuck in a refractory resting phase with stem cells inhibited. Two experiments with different diets and ages looked opposite, so dose and timing matter. This is animal evidence. Suo 2021

What the studies show

• A systematic review of 47 studies on toxic agents and alopecia found thallium, mercury, selenium and colchicine had the strongest links to hair loss, and listed vitamin A among agents with described incidents. Yu 2018
• A review of micronutrients in pattern hair loss (49 articles) discusses vitamin A as one where imbalance matters, with inconsistent evidence. Wang 2024
• We found no trial showing vitamin A supplements regrow hair in people who are not deficient.

Side effects and safety

The European Food Safety Authority's adult upper limit for preformed vitamin A (retinol and retinyl esters, not carotenoids) is 3,000 micrograms retinol equivalents a day, including in pregnancy and breastfeeding. It also advises smokers to avoid beta-carotene supplements. Chronic excess can harm the liver and bones, and high doses of retinoids cause birth defects, so avoid extra vitamin A in pregnancy. Check multivitamin and hair-gummy labels.

Bottom line

Do not supplement beyond need. Eat a normal diet and avoid stacking retinol-containing products. If shedding follows isotretinoin or acitretin, talk to your prescriber. Discuss with a doctor.

Fun facts

• Both too little and too much vitamin A have been linked to hair problems, a rare case where a vitamin is a hazard when over-supplemented. Yu 2018