Inadequate nutrition is a self-evident cause of ill health, and a major contributor to the high death rate among infants and young children in developing countries. The lack of basic micronutrients affects brain development in the foetus and infants during the first two years of life. This is often irreversible, lowering IQ and affecting cognitive levels. Micronutrient deficiencies in humans have been recognized by the WHO as the world's most important primary health care problem.
At least two billion people in the world are deficient in one or several micronutrients. Over the past 30 years of the Green Revolution, which has improved dietary energy consumption of most of the world's population, the percentages of women and children who suffer from nutrient deficiencies in many developing countries has actually increased. These nutrient deficiencies are compounded by parasitic and infectious diseases, water and air pollution, land degradation, and in affluent areas of developing countries, by the increasing incidence of diabetes and heart disease.
Particularly in developing countries, people whose staple diet is cereals or cassava are dangerously low in micronutrients such as iron, zinc, iodine and Vitamin A. The most serious dietary deficiencies are: protein-calorie malnutrition (because of its high mortality rate, its wide prevalence and the irreversible physical and mental damage it may cause); xerophthalmia, vitamin A deficiency, (because of its contribution to mortality of malnourished children, its relatively wide prevalence and the dramatic irreversible damage it causes, namely blindness); nutritional anaemias, iron deficiency anaemia and megaloblastic anaemias (because of their wide distribution, their contribution to mortality from many other conditions and their effects on working capacity); endemic goitre, iodine deficiency, (because of its wide distribution). In some specific areas of the world, other nutritional problems such as beriberi, vitamin B1 deficiency; pellagra, nicotinic acid deficiency associated with protein deficiency; or rickets, vitamin D deficiency, may be of considerable importance.