Vitamin A: Food Sources, Safe Intake and Why Excess Can Be Harmful

Vitamin A sits in an unusual position among vitamins: deficiency is rare in the UK, requirements are readily met by an ordinary diet, and the more important public health message is about not taking too much. It is fat-soluble, it accumulates, and excess has well-documented consequences — including in pregnancy.

Key points

• UK reference nutrient intakes are 700 µg a day for men and 600 µg a day for women.
• Vitamin A contributes to normal iron metabolism, maintenance of normal mucous membranes and normal skin, maintenance of normal vision, normal functioning of the immune system, and it has a role in cell specialisation.
• Preformed vitamin A (retinol) comes from animal foods; beta-carotene from plants is converted as needed and does not carry the same toxicity risk.
• NHS advice: avoid more than 1.5 mg (1,500 µg) a day from food and supplements combined, because higher long-term intakes may weaken bones in later life.
• Pregnant women, or those who might become pregnant, should avoid liver, liver products, cod liver oil and any supplement containing retinol unless a doctor advises otherwise.

What vitamin A is

"Vitamin A" covers two distinct groups:

Preformed vitamin A (retinoids) — retinol, retinal, retinyl esters — found in animal foods and in some supplements. Absorbed efficiently and stored in the liver. This is the form associated with toxicity.

Provitamin A carotenoids — mainly beta-carotene, also alpha-carotene and beta-cryptoxanthin — found in coloured fruits and vegetables. The body converts these to retinol at a rate governed by need, which is why high dietary beta-carotene does not cause vitamin A toxicity. Very high intakes may turn skin harmlessly orange-yellow (carotenaemia).

Labels express vitamin A in micrograms of retinol equivalents (µg RE) or, on older products, international units.

What it does in the body

Retinal is a component of rhodopsin, the pigment that enables vision in low light — which is why night blindness is an early sign of deficiency. Retinoic acid regulates gene expression involved in cell differentiation, contributing to the maintenance of epithelial tissue, including skin and mucous membranes, and to normal immune function. Vitamin A also has an authorised role in normal iron metabolism.

Globally, vitamin A deficiency is a major cause of preventable childhood blindness. In the UK it is uncommon, occurring mainly with fat malabsorption conditions such as cystic fibrosis, coeliac disease, pancreatic insufficiency or liver disease.

Food sources and UK examples

Retinol (animal sources):

• Liver and liver products such as pâté — extremely concentrated
• Cheese
• Eggs
• Oily fish
• Milk and yoghurt
• Fortified spreads

Beta-carotene (plant sources):

• Carrots
• Sweet potato
• Butternut squash
• Spinach, kale and other dark green leafy vegetables
• Red peppers
• Mango, apricots and cantaloupe melon

Carotenoids are fat-soluble, so absorption improves when eaten with some fat — a drizzle of oil on roasted vegetables is genuinely useful.

Who may be at risk

Low intake or deficiency is uncommon in the UK, but risk is higher in:

• People with fat malabsorption (cystic fibrosis, coeliac disease, pancreatic or liver disease)
• People with very restricted diets or eating disorders
• People after certain bariatric surgery procedures

Excess intake is the more realistic UK concern, particularly in:

• Regular liver eaters — a single portion of liver can supply many times the daily requirement
• People taking cod liver oil alongside a multivitamin
• People stacking several supplements containing retinol
• Older adults, where long-term high intakes are linked with reduced bone mineral density and fracture risk

What research says about supplements

• Correcting deficiency is effective and, in deficient populations, vitamin A supplementation in children is a well-established public health intervention. This does not translate into benefit for well-nourished UK adults.
• Beta-carotene supplements and lung cancer. Two large trials in smokers and people exposed to asbestos found increased lung cancer incidence with high-dose beta-carotene supplements. Guidance is that smokers and former smokers should avoid high-dose beta-carotene supplements. Dietary beta-carotene from food does not carry this signal.
• Skin and acne. Prescription oral retinoids are potent medicines with strict monitoring and pregnancy prevention requirements. They are not comparable to vitamin A supplements, and taking vitamin A supplements for acne is not supported and risks toxicity.
• Eye health. Vitamin A contributes to maintenance of normal vision. Specific formulations studied for age-related macular degeneration are a separate clinical topic; those containing beta-carotene were reformulated because of the smoker risk above.

Safety, upper limits and interactions

• NHS guidance: do not take more than 1.5 mg (1,500 µg) of vitamin A a day from food and supplements combined. If you eat liver weekly, avoid vitamin A supplements altogether.
• Acute toxicity from a very large dose causes nausea, headache, blurred vision and dizziness.
• Chronic excess can cause dry skin, hair loss, bone and joint pain, liver damage, headache from raised intracranial pressure, and reduced bone density.
• Pregnancy: high retinol intake is teratogenic. Avoid liver, liver products (including pâté), cod liver oil and retinol-containing supplements. Beta-carotene from food is not a concern.
• Interactions: caution with oral retinoid medicines such as isotretinoin or acitretin (additive toxicity), and with anticoagulants at very high intakes. People with liver disease or high alcohol intake are more susceptible to hepatotoxicity.
• Smokers and former smokers should avoid high-dose beta-carotene supplements.

Choosing a supplement responsibly

• Most UK adults do not need one. Diet covers the requirement.
• Add up total retinol across multivitamins, cod liver oil and any single-nutrient product.
• Prefer beta-carotene in a supplement if you want a margin of safety — with the exception noted for smokers.
• Check pregnancy suitability; pregnancy multivitamins are formulated without retinol for this reason.
• If you eat liver regularly, treat that as your vitamin A source and skip supplements.

Frequently asked questions

How much vitamin A do I need?

The UK reference nutrient intake is 700 µg a day for men and 600 µg a day for women, normally met from food.

Can you take too much vitamin A?

Yes. The NHS advises keeping total intake from food and supplements below 1.5 mg (1,500 µg) a day, as long-term higher intakes may weaken bones. Acute high doses cause nausea, headache and blurred vision.

Why should pregnant women avoid liver and cod liver oil?

Both are very high in preformed vitamin A (retinol), which can harm a developing baby at high intakes. Pregnancy supplements are formulated without retinol.

Is beta-carotene safer than retinol?

For toxicity, yes — the body regulates its conversion. However, smokers and former smokers should avoid high-dose beta-carotene supplements because of increased lung cancer risk seen in trials.

Will carrots improve my eyesight?

Vitamin A contributes to the maintenance of normal vision, and deficiency causes night blindness. In someone with adequate intake, eating more carrots will not improve vision beyond normal.

Can I take vitamin A for acne?

No. Prescription retinoid medicines are different from vitamin A supplements and require medical supervision. Taking vitamin A supplements for acne risks toxicity. Speak to a GP or pharmacist about acne treatment.

Conclusion

Vitamin A is essential, and in the UK the practical question is usually restraint rather than intake. A varied diet with coloured vegetables and normal dairy or eggs meets the requirement without effort. If you take supplements, add up your total retinol; if you are pregnant or planning pregnancy, avoid retinol supplements, liver and cod liver oil; and if you smoke, avoid high-dose beta-carotene.