Vitamin A can be stored in the body, and thus a supplement to correct a dietary deficiency does not have to be given on a daily basis. This includes breast feeding women from families who cannot afford to buy a diet with many vitamin A rich foods, babies from poor families who are not breast fed and babies and children who have an unbalanced diet. A disadvantage of a supplementation programme is that coverage of those most at need is not guaranteed. Children may not be attending a health care centre until the deficiency is severe or those most at need may not attend a health care centre at all. It is also dependent on a good distribution network and on health workers remembering to give the supplement to those in need.
Many different definitions exist for fortification and enrichment.
Both involve the addition of micro-nutrients that either were or were not present before processing took place. The definition may also depend on whether or not the addition of the micro-nutrient is to prevent a public health problem. For some micro-nutrients where a deficiency is identified a dietary source may not be available. With some micro-nutrients a food source may be available, but not affordable, as is the case with iron. This nutrient is found in animal products, which are not always available to poor people, especially in urban areas.