Essential nutrient

An essential nutrient is a nutrient required for normal body functioning that cannot be synthesized by the body. Categories of essential nutrient include vitamins, dietary minerals, essential fatty acids and essential amino acids.

Different species have very different essential nutrients. Most essential nutrients are substances that are metabolically necessary but cannot be synthesized by the organism. Dietary minerals, for example, cannot be synthesized in biological systems, so (for example) a human must obtain the iron they need to build hemoglobin from their diet (of course, this iron is recycled as long as possible, but some is inevitably lost, for example during menstruation).

Most essential nutrients are needed only in small quantities, and are stored and reused by the body. As a result, unlike absence of air or water for humans, absence of essential nutrients usually leads only gradually to the development of a deficiency disease.

Nutritional wisdom is that it is difficult, if not impossible, to isolate all of the substances in our food which are important to good nutrition. Therefore nutritionists advise us to eat as wide a range of foods which are as little processed as possible. This gives us the best chance of regularly obtaining small amounts, at least, of a wide range of essential nutrients, and reduces the chance of poor nutrition and ill health that may result. Further advice on essential nutrition will be based on the circumstances of the person, e.g. their age, occupation, even their location.

Some essential nutrients may be toxic in large doses (see hypervitaminosis or the nutrient pages themselves below); for example, an iron overdose can lead to the production of free radicals beyond what the body's antioxidant system can handle. Others can sometimes be taken in amounts several orders of magnitude larger than in a typical diet, with no apparent ill effects. Linus Pauling says of vitamin B3, (either niacin or niacinamide), "What astonished me was the very low toxicity of a substance that has such very great physiological power. A little pinch, 5 mg, every day, is enough to keep a person from dying of pellagra, but it is so lacking in toxicity that ten thousand times as much can [sometimes] be taken without harm." A similar statement can be made about vitamin C and some other vitamins.

List of essential nutrients

 * Essential fatty acids:
 * Linolenic acid (the shortest chain omega-3 fatty acid)
 * Linoleic acid (the shortest chain omega-6 fatty acid)
 * Essential amino acids necessary for all humans:
 * Tryptophan
 * Lysine
 * Methionine
 * Phenylalanine
 * Threonine
 * Valine
 * Leucine
 * Isoleucine
 * Essential amino acids necessary for human children and not adults:
 * Histidine
 * Arginine
 * Vitamins:
 * Biotin
 * Choline
 * Folate
 * Niacin
 * Pantothenic acid
 * Riboflavin (vitamin B2, vitamin G)
 * Thiamin (vitamin B1)
 * Vitamin A (retinol)
 * Vitamin B6 (pyridoxine, pyridoxamine, or pyridoxal)
 * Vitamin B12 (cobalamin)
 * Vitamin C (ascorbic acid)
 * Vitamin D (calciferol)
 * Vitamin E (tocopherol)
 * Vitamin K (naphthoquinoids)
 * Dietary minerals:
 * Chromium (Cr)
 * Bromine (Br)
 * Cobalt (Co)
 * Copper (Cu)
 * Germanium (Ge)
 * Iodine (I)
 * Iron (Fe)
 * Magnesium (Mg)
 * Manganese (Mn)
 * Molybdenum (Mo)
 * Potassium (K)
 * Selenium (Se)
 * Zinc (Zn)
 * Calcium (Ca)
 * Phosphorus (P)
 * Sodium (Na)
 * Sulfur (S)
 * Vanadium (V)
 * Secondary dietary minerals:
 * Bismuth (Bi) (suspect)
 * Boron (B)
 * Fluorine (F) (necessity unknown in humans)
 * Nickel (Ni)
 * Rubidium (Rb) (suspect)
 * Silicon (Si)
 * Strontium (Sr) (suspect)
 * Tellurium (Te) (suspect)
 * Tin (Sn) (may depend on definition of essential -- see reference)
 * Titanium (Ti) (suspect)
 * Tungsten (W) (some organisms use tungsten rather than molybdenum)