Vitamin A

Retinol from animal foods, and carotenoids from plants that your body converts. Essential for vision in dim light, immune function and skin, and one of the few vitamins where excess is genuinely dangerous.

Needed to see in dim light — it forms rhodopsin, the pigment in the retina. Also maintains the surface tissues of the eye, gut and airways, and is required for immune function and normal growth.

• Liver
• Egg yolk
• Butter and cheese
• Oily fish
• Carrots and sweet potato (as beta-carotene)
• Dark leafy greens
• Red peppers

Fat-soluble — needs some fat in the meal.

900 µg RAE (men) · 700 µg RAE (women) for most adults. The upper limit, past which harm becomes likely, is 3,000 µg preformed retinol.

Reference intakes are population figures. Pregnancy, illness, age and medication all move an individual’s needs, which is one of several reasons this page is information rather than advice.

A sustained shortage has a name here: Xerophthalmia. That is worth pausing on — nutrients whose deficiency earned a name are the ones where the consequences were severe enough, historically, to be described as a disease.

Most at risk: Rare where food is plentiful. Fat malabsorption — cystic fibrosis, coeliac disease, pancreatic insufficiency — is the usual cause in wealthy countries.

Uncommon where food is plentiful. Occurs with fat malabsorption — coeliac disease, cystic fibrosis, pancreatic insufficiency, liver disease — and with very restricted diets.

Night blindness first, then drying of the cornea. Still the leading cause of preventable childhood blindness worldwide. Also raises susceptibility to infection.

Every sign here has other, often likelier, explanations. A list of symptoms is a reason to look into something, never a diagnosis.

Serum retinol is held steady until liver stores are substantially depleted, so it detects deficiency late. Night vision difficulty is often the earlier signal.

Liver is extremely rich — to the point of caution. Orange and dark green vegetables supply carotenoids, and because it is fat-soluble, eating them with some fat improves absorption considerably.

Preformed vitamin A accumulates and is toxic in excess, affecting liver and bone. High doses cause birth defects, so it matters in pregnancy. Beta-carotene from food does not carry the same risk, since conversion is regulated.

Preformed vitamin A accumulates. Too much causes headache, bone pain, liver damage and hair loss, and — importantly — causes birth defects. Pregnant women should avoid liver and high-dose supplements. Beta-carotene from food does not do this; the body converts only what it needs, though very high intakes turn the skin orange harmlessly.

Interactions: Isotretinoin and other retinoid medicines add to the total; do not supplement alongside them.