What is vitamin A for: functions, sources, and dose

Vitamin A is a fat-soluble vitamin. Unlike vitamin C, which you need to replenish daily because you excrete the surplus, your body stores vitamin A in the liver. So you do not have to take in an exact amount every single day — enough on average across a week is sufficient. Vitamin A comes in two forms: as retinol from animal products, and as beta-carotene from plant-based food, which your body converts into vitamin A when it needs it.

The European Food Safety Authority (EFSA) has approved six health claims for vitamin A. Those six are everything a manufacturer is officially allowed to put on a label; anything beyond them is marketing or research in progress. Below we walk through all six, with the numbers and sources. And at the end, we point out when additional vitamin A is actually a bad idea — because vitamin A is one of the few vitamins where an excess can genuinely be harmful, and you rarely hear that from a seller.

What does vitamin A actually do in your body?

Vitamin A has six EFSA-recognised functions. Some are widely known (eyes, skin), others are rarely mentioned (iron metabolism, cell division).

The six functions, in the official wording from EFSA regulation 432/2012:

Vitamin A contributes to the maintenance of normal vision. Vitamin A contributes to the maintenance of normal skin. Vitamin A contributes to the maintenance of normal mucous membranes. Vitamin A contributes to the normal function of the immune system. Vitamin A contributes to normal iron metabolism. Vitamin A has a role in the process of cell specialisation.

Below, what each function means in practice — and what it does not mean.

Vitamin A and your vision

The best-known function. Vitamin A is a building block of rhodopsin, the pigment in your retina that converts light into a signal to your brain. You notice this mainly in the dark: with too little vitamin A, your eye recovers more slowly after a bright flash of light, and over time night blindness develops — difficulty seeing in twilight.

Worldwide, vitamin A deficiency is the leading preventable cause of blindness in children (World Health Organization). In the Netherlands this is virtually a non-issue; here almost everyone gets more than enough through food. What vitamin A does not do: improve your visual acuity if you already get enough. It keeps a normal process normal, not above normal.

A persistent story: that eating lots of carrots improves your night vision. That comes from British propaganda in the Second World War, intended to hide the fact that pilots were using radar. Enough vitamin A prevents night blindness caused by deficiency; extra does not give you super-sight.

Vitamin A for your skin and mucous membranes

Vitamin A directs the production and renewal of skin cells. It contributes to the maintenance of normal skin and of normal mucous membranes — the moist tissue in your airways, gut, mouth and eyes that acts as a barrier against pathogens. With a deficiency, the skin becomes dry and rough and damaged tissue heals more slowly.

The strongest form of vitamin A for the skin is in cosmetics (retinol) and in retinoids prescribed by a doctor — which is something other than the vitamin A you get from food. Food keeps your skin normal from the inside; it makes no claim to an effect beyond that.

Here too: more is not better. Enough vitamin A keeps cell renewal going. A surplus from supplements does not improve your skin and can, as set out below, actually be harmful.

Vitamin A and your immune system

Vitamin A contributes to the normal function of the immune system. It works in two ways: it keeps intact the mucous membranes that form the first physical barrier against intruders, and it plays a role in the production and function of immune cells. There is a reason vitamin A used to be called the 'anti-infection vitamin'.

As with vitamin C: a deficiency lowers your resistance, but extra on top of a normal intake does not lift your immunity to a higher level. Anyone who gets enough yet still takes a supplement 'for immunity' is paying for an effect that is not there.

Retinol and beta-carotene: two forms, one vitamin

Vitamin A enters your body in two forms. Retinol is the ready-made animal form: liver, oily fish, egg yolk, butter and full-fat dairy. Beta-carotene is the plant-based precursor, found in orange and green vegetables — carrot, sweet potato, pumpkin, spinach, kale — and in fruit such as mango and apricot. Your body converts beta-carotene into vitamin A.

That conversion is exactly why beta-carotene from food is safe: your body only produces what it needs and leaves the rest alone. As a result you cannot overdose on vitamin A through vegetables and fruit. You can on retinol from liver or supplements — more on that below.

Practically: beta-carotene is fat-soluble, so a little fat helps absorption. Olive oil over your braised carrots, a knob of butter through the spinach, a handful of nuts with your salad. Raw and without fat, your body absorbs considerably less.

How much vitamin A do you need per day?

The Dutch Health Council sets 800 micrograms per day for adult men and 680 micrograms for adult women (expressed in retinol equivalents). Pregnant women 750 micrograms, breastfeeding women 1,100 micrograms, and children aged 1 to 3 years 285 micrograms.

How far do you get with food? According to the Netherlands Nutrition Centre, 55 grams of cooked carrot provides about 470 micrograms, 70 grams of cooked spinach around 228 micrograms, and a 250-millilitre glass of semi-skimmed milk around 38 micrograms. Beef liver is an outlier: 100 grams already contains over 27,000 micrograms — more than ten times a daily requirement, and precisely why liver should be eaten in moderation.

In the Netherlands a real vitamin A deficiency is rare. With a varied pattern that regularly includes orange and green vegetables, you almost always meet your daily requirement. A supplement is unnecessary for most people.

Too much vitamin A: when you are better off not taking a supplement

Because vitamin A is fat-soluble and stored in your liver, an excess accumulates — unlike vitamin C, which you simply excrete. The acceptable upper limit for adults is 3,000 micrograms per day (Netherlands Nutrition Centre, in line with the European norm). Prolonged excess retinol can strain the liver, accelerate bone loss and cause headaches. These are three situations in which extra vitamin A is not a good idea.

During pregnancy or if you want to become pregnant. Too much retinol increases the risk of birth defects. Avoid liver and liver products, and do not take a supplement containing retinol (vitamin A) unless your doctor prescribes it. Beta-carotene from vegetables and fruit is safe.

If you smoke. High doses of beta-carotene as a supplement (from 15 milligrams per day) have been linked in two large studies (the ATBC and CARET trials) to an increased risk of lung cancer in smokers. Beta-carotene from ordinary food is not a problem; this concerns specifically high-dose supplements.

If you already eat varied meals. Do you have vegetables and fruit every day, with something orange or green regularly? Then you get enough vitamin A and a supplement adds nothing. Your money is better spent on good vegetables than on a pill.

Vitamin A is one of the few vitamins where more is genuinely not better. The margin between enough and too much is smaller than for water-soluble vitamins. When in doubt: choose food over supplements, and consult your GP before taking a vitamin A supplement — certainly around a pregnancy.