It can also result from a lack of any combination of these. Deficiencies of protein and calories, for example, usually occur together, and because protein is essential for growth, such protein-calorie malnutrition can have grave effects on children, including mental retardation. Vitamin and mineral deficiencies can result in a range of health problems. Calcium deficiency inhibits the formation of bones and teeth in children. Loss of taste and smell can result from zinc deficiency.
Iodine deficiency causes goiter, or enlargement of the thyroid gland.
Some nutrition research indicates that extreme vegetarianism, imposed by parents' dietary choices, can cause malnutrition in children. Iron and zinc deficiencies have been especially noted in diets heavily dependent on plant products. In general, normal growth and development of children is strengthened by appropriate intake of eggs, dairy products, meat, and fish. In developed nations, obesity is the most common form of malnutrition. It can lead to diabetes and hormonal disturbances and can also contribute to heart, kidney, and circulatory diseases.