Vitamin A: Too Little and Too Much
Vitamin A keeps your eyes, skin and immune system working. Deficiency is a leading cause of preventable blindness in children worldwide, but rare in Australia, where too much from supplements is the more common risk.
Too little: deficiency
- First sign: night blindness, trouble seeing in dim light
- Dry eyes, then damage to the cornea (xerophthalmia), which can cause permanent blindness
- Dry skin and more frequent or severe infections
- In Australia, mostly with absorption problems: cystic fibrosis, Crohn’s disease, coeliac disease, liver disease, after weight-loss surgery
- Worldwide, about 190 million preschool children are affected
Too much: toxicity
- Headache, blurred vision, nausea, dizziness, dry skin, bone and joint pain, and liver damage.
- Pregnancy: high doses of preformed vitamin A and retinoid medicines (such as isotretinoin for acne) can cause birth defects. Avoid supplements above 3,000 micrograms a day, and use pregnancy-specific multivitamins.
- Smokers: high-dose beta-carotene supplements increased lung cancer in two large trials of smokers. Beta-carotene from food is fine.
- Liver is very high in vitamin A. Pregnant women are advised to limit it.
Food sources
- Ready-made vitamin A: liver, eggs, dairy, oily fish.
- Beta-carotene (the body converts it): carrots, sweet potato, pumpkin, spinach, mango, rockmelon and red capsicum.
- Adults need about 700 (women) to 900 (men) micrograms a day.
See your GP if
- You have trouble seeing at night, especially with a gut or liver condition
- You’re pregnant or planning a pregnancy and take supplements or eat liver often
- You smoke and take beta-carotene or a high-dose antioxidant supplement
Weird history
- Eating polar bear or husky liver can cause acute vitamin A poisoning. Some have suggested this contributed to Xavier Mertz’s death on Douglas Mawson’s 1912 Antarctic expedition, although that theory has been challenged.
- Too much beta-carotene can turn your skin orange (carotenaemia). It’s harmless and fades.
Common questions
What is the first sign of vitamin A deficiency?
Night blindness: trouble seeing in dim light. Without treatment it can progress to dry eyes and damage to the cornea.
Is vitamin A safe in pregnancy?
Food sources are fine, but avoid high-dose supplements of preformed vitamin A (over 3,000 micrograms a day), liver in large amounts and retinoid medicines, which can cause birth defects.
Should smokers take beta-carotene?
No. High-dose beta-carotene supplements increased lung cancer in smokers in two large trials. Getting it from fruit and vegetables is safe.
Can eating too many carrots turn your skin orange?
Yes. It’s called carotenaemia, and it’s harmless. It fades when you eat less beta-carotene.
Helpful resources
- Healthdirect: Vitamins and mineralsPlain-English Australian Government guide. Free.
- Pregnancy, Birth and BabyAustralian Government pregnancy advice, including supplements. Free.
Evidence and more information
- NIH Office of Dietary Supplements: Vitamin A
- MJA 2005: Mawson and Mertz, a re-evaluation
- Nutrient Reference Values for Australia and New Zealand (Eat for Health)
maladywise.com/vitamin-a/