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Essential nutrients

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Essential nutrients

An essential nutrient is a nutrient required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health (e.g. niacin, choline), and thus must be obtained from a dietary source. Essential nutrients are also defined by the collective physiological evidence for their importance in the diet, as represented in e.g. US government approved tables for Dietary Reference Intake.[1]

Some categories of essential nutrients include vitamins, dietary minerals, essential fatty acids, and essential amino acids. Different species have very different essential nutrients. For example, most mammals synthesize their own ascorbic acid, and it is therefore not considered an essential nutrient for such species. It is, however, an essential nutrient for human beings, who require external sources of ascorbic acid (known as Vitamin C in the context of nutrition).

Many essential nutrients are toxic in large doses (see hypervitaminosis or the nutrient pages themselves below). Some can be taken in amounts larger than required in a typical diet, with no apparent ill effects. Linus Pauling said 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."[2]

For humans

Fatty acids

Essential fatty acids cannot be synthesized by humans, as humans lack the desaturase enzymes required for their production.

α-Linolenic acid is not used by the body in its original form. It is broken down by the body into the required long-chain polyunsaturated fatty acids eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6). EPA and DHA can also be consumed from a direct source by consuming fish or fish oil.

Linoleic acid is not used by the body in its original form either. It is broken down by the body into the required long-chain polyunsaturated fatty acids gamma-linolenic acid (GLA, 18:3), dihomo-gamma-linolenic acid (DGLA, 20:3) and arachidonic acid (AA, 20:4).

Omega-9 fatty acids are not essential in humans, because humans generally possess all the enzymes required for their synthesis.

Amino acids

  • Essential amino acids necessary for preterm children but not healthy individuals:

Carbohydrates

No carbohydrate is an essential nutrient in humans.[4] Carbohydrates can be synthesized from amino acids and fatty acids, by de novo synthesis.

Vitamins

Dietary minerals

The required quantity varies widely between nutrients. At extremes, a 70 kg human contains 1.0 kg of calcium, but only 3 mg of cobalt.

Elements with speculated role in human health

Many elements have been implicated at various times to have a role in human health. For none of these elements, however, has a specific protein, complex or dietary reference intake been established.

References

Further reading

See also

Food portal
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