Diseases of nutrient deficiencies

Abstract

Essential nutrients vary enormously in their body content and requirements. They are each crucial for normal metabolism, they interact with one another, and they act differently when metabolism is altered by either nutrient deficiencies or excesses or by disease. Their deficiencies can also affect the metabolism of invading microorganisms. In poverty, numerous nutrient deficiencies and numerous infections coexist and are synergistic, forming a vicious spiral that leads to malnutrition. The most common form of this, affecting about half the children living in poverty in the developing world, is chronic stunting. It is preventable. This chapter focuses on nutrient deficiencies and their effects. Specific micronutrients, important to health, are included: iron, zinc and vitamin A, which have deficiencies that together appear to be responsible for nearly 20% or 2 million deaths a year in young children; folic acid and vitamin B12, which also contribute to the ubiquitous problem of anemia; and selenium, thiamin, and vitamin D as examples for which we have learned much from history and geography. For each nutrient, advice is given on estimation of nutrient status. For several nutrients, however, the tests available are not yet sufficiently specific. Zinc is an example ; we still have no reliable measure of its status for either clinical use or population studies. Finally, the major problem of childhood malnutrition is outlined. Our knowledge and understanding of nutrient metabolism is sparse, but still progressing.