Zambia is launching a scheme to tackle disease resulting from vitamin deficiency - by fortifying sugar.

Small amounts of vitamin A are being added to sugar to try to counter the effects of a deficiency of the vitamin which is linked to malnutrition.

They include reduced ability to fight off infection, impaired night vision and, in extreme cases, death.

The BBC Science correspondent says food fortification programmes have been a success elsewhere in the world, but that Zambia is the first country in sub-Saharan Africa to use food supplements to combat vitamin A deficiency.