A micronutrient is any substance that the human body requires from it's diet in very small daily quantities (generally, less than a gram a day) where the lack of obtaining the substance in sufficient quantities will lead to the development of a disease. They are distinguished from macronutrients - carbohydrates, fats and proteins, which provide the body with the energy it requires. In general, there are two types of micronutrients:
- Minerals - chemical elements that the body requires in small amounts as part of its metabolic processes, such as calcium, sodium and iron in fairly substantial quantities (several hundred milligrams a day), and others which it requires in much lower quantities, such as magnesium, zinc and iodine. Lack of a vital mineral can lead to diseases that can have other causes, such as anemia for iron deficiency.
- Vitamins - complex chemicals that also assist with metabolic processes. By definition, the lack of a vitamin causes a specific disease, such as scurvy for a lack of vitamin C.
In most cases, micronutrient supplements are unnecessary and are not otherwise beneficial to health. However, they may be required by persons who cannot obtain the necessary micronutrients from their diet. The vast majority of people with a balanced diet easily obtain their daily minimum requirements. In addition, the body is capable of storing some micronutrients. For example, vitamin B12 and other fat soluble vitamins are stored in the liver, and the body can meet its calcium needs by taking it from bones. However, others, such as Vitamin C and sodium, which are water soluble, generally have to be replenished on a daily basis.