Vitamin A supplements: forms, needs, risks and pregnancy

Vitamin A isn't a trivial ingredient to add "just in case." It's essential for vision, immunity, skin, and embryonic development. It's also fat-soluble: the body stores it, especially in its preformed state. This characteristic changes everything when talking about supplements.

Two families need to be distinguished. Retinol and retinyl esters correspond to preformed vitamin A, found in animal-based foods and certain supplements. Provitamin carotenoids, such as beta-carotene, mainly come from colorful plants; the body converts a portion of them into vitamin A. The two label lines don't carry the same risk. [1][3]

Preformed vitamin A is directly usable by the body. It can therefore accumulate more easily when it comes from several sources. Provitamin carotenoids go through a regulated conversion, which varies between people and with intake.

Authorities use units such as RAE or RE to compare vitamin activity. The NIH ODS lists benchmarks of 700 µg RAE/day for adult women, 900 µg for adult men, and 770 µg during pregnancy. These values help assess needs; they don't become an automatic supplement dose. [1][5]

Dairy products, eggs, certain fish, liver, and cod liver oil mainly provide preformed vitamin A. Carrots, sweet potatoes, squash, spinach, and other colorful vegetables mainly provide carotenoids.

Liver deserves a special mention. It's a food extremely concentrated in preformed vitamin A. In someone who already eats liver, a multivitamin with retinol or a targeted supplement can quickly make the cumulative total harder to track.

Pregnancy increases the physiological need, without making vitamin A supplementation routine. The point of caution mainly concerns high-dose preformed vitamin A. In 2024, EFSA set a tolerable upper intake level of 3,000 µg RE/day for preformed vitamin A in adults, including pregnant and breastfeeding women. An upper limit isn't a target to reach. [2]

Dietary beta-carotene isn't assessed the same way. EFSA's data show no indication of adverse effects linked to dietary beta-carotene; the opinion does, however, recommend avoiding beta-carotene supplements in smokers and heavy former smokers. [2]

This recommendation isn't theoretical: two large controlled trials (ATBC and CARET) tested high-dose synthetic beta-carotene supplements (20 to 30 mg per day) in heavy smokers. Both trials had to be stopped earlier than planned: the ATBC trial reported about an 18% increase in lung cancers and 8% in overall mortality in the supplemented group, and the CARET trial about a 28% increase in lung cancers and 17% in overall mortality. This is one of the best-documented examples where a supplement, meant to reproduce a benefit observed with diet, produced the opposite effect in a specific at-risk population.

Excess preformed vitamin A can cause headaches, nausea, skin disorders, bone pain, abnormal lab results, and liver damage. The risk depends on the dose, the duration, the form, and the cumulative total from food or other supplements.

Retinoids used in dermatology raise the level of caution further. They already belong to a family close to vitamin A and require strict monitoring, particularly around pregnancy.

A documented deficiency, malabsorption, certain medical situations, or specific needs can justify supplementation. In that case, the choice of form and dose isn't made at random. Copying the number on a box or adding up several "vision," "skin," and "immunity" products mainly risks losing track of the cumulative total.

Before buying, note the supplements already taken, identify the form of vitamin A, add in concentrated sources like liver or cod liver oil, then look at the context: pregnancy, smoking, liver disease, retinoid treatment.

Vitamin A perfectly illustrates the "more is better" trap. The needs are real, and so is the excess. A supplement is worth discussing mainly when the situation calls for it; the priority remains distinguishing retinol from beta-carotene, then keeping track of the cumulative total.