Essential nutrient

From WikiMD
Jump to navigation Jump to search

An essential nutrient is a nutrient required for normal human body function 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 converted 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, fish oil or algal oil (vegetarian source).

Linoleic acid is not used by the body in its original form either. It is converted 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

Carbohydrates

Carbohydrates are sugar molecules and chains of sugar molecules. No individual carbohydrate is an essential nutrient in humans.[4] Glucose can be synthesized from amino acids and glycerol, which is obtained from fat metabolism, by de novo synthesis (called gluconeogenesis), but in insufficient quantities to maintain normal brain metabolism.[citation needed] However, the body can adapt to this state by producing ketones (a state called ketosis) to fuel the brain, which can only use glucose and ketones for fuel, unless carbohydrate stores are repleted.[4]

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.[citation needed]


Other

For plants

Further reading

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

See also

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. December 2001.
  2. Page 24.
  3. J D Kopple and M E Swendseid (May 1975). "Evidence that histidine is an essential amino acid in normal and chronically uremic man". J Clin Invest. 55 (5): 881–891. doi:10.1172/JCI108016. PMC 301830. PMID 1123426.
  4. 4.0 4.1 Westman, EC (2002). "Is dietary carbohydrate essential for human nutrition?". The American journal of clinical nutrition. 75 (5): 951–3, author reply 953–4. PMID 11976176.
  5. "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. October 2009.
  6. R. Bruce Martin "Metal Ion Toxicity" in Encyclopedia of Inorganic Chemistry, Robert H. Crabtree (Ed), John Wiley & Sons, 2006. doi:10.1002/0470862106.ia136

Portions of content adapted from Wikipedias article on Essential nutrient licensed under GNU FDL.Portal:Food

Calories and Nutritional Information of Foods


Heart-greens-1000.jpg

Glossary of healthy eating | Nutritional value of foods: UK Foods | US Foods | Dietary Supplements | Nutrition values of foods | Nutrition lookup (USDA) Portions of content adapted from Wikipedias article on Essential nutrient licensed under GNU FDL.

W8MD weight loss logo

Ad. Tired of being overweight?. W8MD's insurance Weight loss program can HELP*

Quick links: Medicine Portal | Encyclopedia‏‎‏‎ | Gray's Anatomy‏‎ | Topics‏‎ |‏‎ Diseases‏‎ | Drugs | Wellness | Obesity‏‎ | Metabolic syndrome | Weight loss*
Disclaimer: The entire contents of WIKIMD.ORG are for informational purposes only and do not render medical advice or professional services. If you have a medical emergency, you should CALL 911 immediately! Given the nature of the wiki, the information provided may not be accurate, misleading and or incorrect. Use the information on this wiki at your own risk! See full Disclaimer.
Link to this page: <a href="http://www.wikimd.org/wiki/Essential_nutrient">Essential nutrient</a>

  • Individual results may vary for weight loss from our sponsors.