Human nutrient requirements are the amounts of different types of nutrients needed to maintain optimal health. Nutrients include calories, fat, carbohydrates, protein, minerals, vitamins, and amino acids. Inadequate levels of certain nutrients can lead to various diseases. In developed countries, nutrient deficiencies serious enough to cause illness are rare.
The most basic of all nutrient requirements is sufficient calories. Calories provide energy for all bodily functions, and it is important to eat enough calories to provide the body with enough energy to meet daily requirements. Children in poor countries may develop a condition called marasmus, which leads to stunted growth. The body does not have sufficient energy to maintain blood sugar levels, so it attacks its own protein in an effort to maintain blood sugar levels.
There are nine essential amino acids that the body requires to synthesize protein. It is important to meet these nutrient requirements because the body cannot produce these amino acids itself. Essential amino acids are valine, threonine, phenylalanine, methionine, leucine, isoleucine, histidine, tryptophan, and lysine. Tryptophyn and lysine are particularly difficult to consume in proper amounts for people on a vegan diet.
Fat is perhaps the easiest of the nutrient requirements to meet. It is easy to consume too much fat, but it is the most concentrated form of energy available. Linoleic acid, arachidonic acid, and linolenic acid are essential fatty acids that the body cannot produce on its own, and must be consumed.
Minerals are an important part of human nutrient requirements. Some nutrients are required in large amounts, while others are required in such small amounts that it is nearly impossible to become deficient. Foods fortified with minerals prevent many deficiencies. One example of this is table salt fortified with iodine. The widespread use of iodine fortified table salt has nearly eliminated iodine deficiency, which can lead to a swelling of the thyroid gland known as a goiter, and mental retardation if an expactant mother is deficient in iodine during pregnancy.
Calcium is a mineral required for nearly all functions in the body, including muscle contractions and blood clotting. Iron is the most common mineral deficiency in developed countries, and leads to anemia. Women are more likely than men to be iron-deficient, because of blood loss from menstruation and increased iron requirements during pregnancy and breast feeding. It is important to be cautious when supplementing iron however, as iron supplements are the most common cause of accidental poisoning in children in the United States.
Not meeting the nutrient requirements for vitamins can lead to various health conditions, depending on the degree of deficiency, and the vitamin. A deficiency in vitamin C can lead to scurvy, a deficiency in vitamin D can lead to rickets in children, and softening of bones in adults. People who do not get enough vitamin K may experience slow blood clotting. Low levels of vitamin E can lead to anemia and damage to the eyes.