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Revision as of 12:28, 8 February 2011

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.

Some categories of essential nutrients include vitamins, dietary minerals, essential fatty acids, and essential amino acids. Water and oxygen are also essential for human health and life, as oxygen cannot be synthesized by the body, and water, while a biochemical reaction product of metabolism, is not created in sufficient amounts. Both are necessary as biochemical reactants in some processes, and water is used in various ways such as a solvent, carrier, and coolant, but neither are considered to be nutrients.

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 be taken without harm." However, it should be noted that large quantities of some vitamins are life-threatening (e.g. excessive amounts of Vitamin D, a fat-soluble nutrient involved in maintaining adequate blood-calcium levels, can lead to nausea, vomiting, stupor, and death via cardiac arrhythmia and arrest).

Fatty acids

See also: Essential fatty acid

Amino acids

See also: Essential amino acid
  • Essential amino acids necessary for human children but not adults:

Vitamins

Dietary minerals

See also: dietary minerals

The required quantity varies widely between nutrients. At one extreme, 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

  1. "National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. Dietary Guidance: DRI Tables". US Department of Agriculture, National Agricultural Library and National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. 2009. {{cite web}}: Cite has empty unknown parameter: |1= (help); Unknown parameter |month= ignored (help)
  2. Pauling, L. (1986). How to Live Longer and Feel Better. New York NY 10019: Avon Books Inc. ISBN 0-380-70289-4.{{cite book}}: CS1 maint: location (link) Page 24.
  3. "National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Elements". US Department of Agriculture, National Agricultural Library and National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. 2009. {{cite web}}: Cite has empty unknown parameter: |1= (help); Unknown parameter |month= ignored (help)
  4. Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
  5. R. Bruce Martin “Metal Ion Toxicity” in Encyclopedia of Inorganic Chemistry, Robert H. Crabtree (Ed), John Wiley & Sons, 2006. DOI: 10.1002/0470862106.ia136
  6. Mertz, W. 1974. The newer essential trace elements, chromium, tin, vanadium, nickel and silicon. Proc. Nutr. Soc. 33 p. 307.

Further reading

  • Hausman, P, 1987, The Right Dose. Rodale Press, Emaus, Pennsylvania. ISBN 0-87857-678-9

See also

Categories: