Salt has long been known to be an excellent vehicle for providing nutrients to large populations because almost everyone consumes it, and it is relatively cheap to fortify

Venkatesh Mannar, University of Toronto

Iodine is already commonly added to salt, but the new technique developed by Venkatesh Mannar of the University of Toronto also allows the addition of iron supplements.

Nearly two billion people, mostly women and children under five years of age in poor countries, are estimated to suffer from IDA.

The condition reduces both physical and mental capacities of sufferers - even mild anaemia may affect the intellectual development of the very young.

Iodine deficiency is a major dietary problem which can lead to severe mental disability, miscarriages and stillbirths.

Scientists have been working for 30 years on a way of adding both iron and iodine to salt without reducing the effect of either nutrient.

Too much salt is, though, associated with poor health, including stroke.

Coating

The iron in the new salt is combined with iodine encapsulated with dextrin, using a process similar to the one used in coating cold tablets. The coating prevents the iodine and iron from interacting with one another or coming into contact with moisture in the salt.

"Salt has long been known to be an excellent vehicle for providing nutrients to large populations because almost everyone consumes it, and it is relatively cheap to fortify," said Mr Mannar, who is executive director of the Micronutrient Initiative - a partnership of developing agencies, UNICEF and the World Bank.

"We found that when you add iron and iodine to the same salt, there are problems with stability, they compete with one another and the iron tends to drive the iodine out," he added.

"So we felt we need to create a barrier between iron and iodine and the way we did it was to take the iron and iodine independently and encapsulate them - coat each grain of iron and iodine with a small coating of dextrin that protects it and keeps it separate from other nutrients."

Once this special salt is eaten, the nutrients are released and absorbed by the body. The flavour, colour and texture of the salt won't be changed by adding the specially coated nutrients, and it could be available in some areas by next year.

However, Mr Mannar believes the scheme will be successful only if governments, health agencies and private industry work together.

The Micronutrient Initiative is now working on adding vitamin A to salt.