Most people will get enough of the nutrient through their normal diet. Vegetarians, however, may need to eat more dark-coloured fruits and vegetables, because new research shows that those foods actually yield half as much vitamin A as previously thought. The amounts do not have to be huge, however. Half a cup of cooked carrots is enough. Cooking doubles the body’s absorption of vitamin A, so people who prefer raw veggies need more.

But vitamin supplements — even a regular multivitamin that contains three times the RDA — can push people over safe levels, the report cautioned. Of most concern are megadoses sold in health food stores. The institute is part of the National Academy of Sciences, a non-profit organisation that advises the federal government and has set the nation’s RDAs for nutrients since 1941. –

In more severe cases, vitamin and mineral deficiencies can lead to anaemia and blindness. The report calls on the food industry to consider adding key vitamins to staple foods to tackle the problem. It also calls for supplements to be made available to millions of people in developing countries. In addition, it urges governments to do more to fight diseases like malaria, measles and diarrhoea which can prevent people from absorbing vitamins and minerals properly. “The overwhelming scope of the problem makes it clear that we must reach out to whole populations and protect them from the devastating consequences of vitamin and mineral deficiency,” said Carol Bellamy, executive director of Unicef.