Misplaced Pages

Latest revision as of 03:29, 18 December 2024

A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted into smaller molecules in the process of releasing energy such as for carbohydrates, lipids, proteins and fermentation products (ethanol or vinegar) leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.

Different types of organisms have different essential nutrients. Ascorbic acid (vitamin C) is essential to humans and some animal species but most other animals and many plants are able to synthesize it. Nutrients may be organic or inorganic: organic compounds include most compounds containing carbon, while all other chemicals are inorganic. Inorganic nutrients include nutrients such as iron, selenium, and zinc, while organic nutrients include, protein, fats, sugars and vitamins.

A classification used primarily to describe nutrient needs of animals divides nutrients into macronutrients and micronutrients. Consumed in relatively large amounts (grams or ounces), macronutrients (carbohydrates, fats, proteins, water) are primarily used to generate energy or to incorporate into tissues for growth and repair. Micronutrients are needed in smaller amounts (milligrams or micrograms); they have subtle biochemical and physiological roles in cellular processes, like vascular functions or nerve conduction. Inadequate amounts of essential nutrients or diseases that interfere with absorption, result in a deficiency state that compromises growth, survival and reproduction. Consumer advisories for dietary nutrient intakes such as the United States Dietary Reference Intake, are based on the amount required to prevent deficiency and provide macronutrient and micronutrient guides for both lower and upper limits of intake. In many countries, regulations require that food product labels display information about the amount of any macronutrients and micronutrients present in the food in significant quantities. Nutrients in larger quantities than the body needs may have harmful effects. Edible plants also contain thousands of compounds generally called phytochemicals which have unknown effects on disease or health including a diverse class with non-nutrient status called polyphenols which remain poorly understood as of 2024.

Types

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Nutrient" – news · newspapers · books · scholar · JSTOR (December 2022) (Learn how and when to remove this message)

Macronutrients

Macronutrients are defined in several ways.

• The chemical elements humans consume in the largest quantities are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, summarized as CHNOPS.
• The chemical compounds that humans consume in the largest quantities and provide bulk energy are classified as carbohydrates, proteins, and fats. Water must be also consumed in large quantities but does not provide caloric value.
• Calcium, sodium, potassium, magnesium, and chloride ions, along with phosphorus and sulfur, are listed with macronutrients because they are required in large quantities compared to micronutrients, i.e., vitamins and other minerals, the latter often described as trace or ultratrace minerals.

Macronutrients provide energy:

• Carbohydrates are compounds made up of types of sugar. Carbohydrates are classified according to their number of sugar units: monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).
• Proteins are organic compounds that consist of amino acids joined by peptide bonds. Since the body cannot manufacture some of the amino acids (termed essential amino acids), the diet must supply them. Through digestion, proteins are broken down by proteases back into free amino acids.
• Fats consist of a glycerin molecule with three fatty acids attached. Fatty acid molecules contain a -COOH group attached to unbranched hydrocarbon chains connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed for construction and maintenance of cell membranes, to maintain a stable body temperature, and to sustain the health of skin and hair. Because the body does not manufacture certain fatty acids (termed essential fatty acids), they must be obtained through one's diet.
• Ethanol is not an essential nutrient, but it does provide calories.The United States Department of Agriculture uses a figure of 6.93 kilocalories (29.0 kJ) per gram of alcohol (5.47 kcal or 22.9 kJ per ml) for calculating food energy. For distilled spirits, a standard serving in the U.S. is 44 ml (1.5 US fl oz), which at 40% ethanol (80 proof) would be 14 grams and 98 calories.

Micronutrients

Micronutrients are essential dietary elements required in varying quantities throughout life to serve metabolic and physiological functions.

• Dietary minerals, such as potassium, sodium, and iron, are elements native to Earth, and cannot be synthesized. They are required in the diet in microgram or milligram amounts. As plants obtain minerals from the soil, dietary minerals derive directly from plants consumed or indirectly from edible animal sources.
• Vitamins are organic compounds required in microgram or milligram amounts. The importance of each dietary vitamin was first established when it was determined that a disease would develop if that vitamin was absent from the diet.

Essentiality

Essential nutrients

An essential nutrient is a nutrient required for normal physiological function that cannot be synthesized in the body – either at all or in sufficient quantities – and thus must be obtained from a dietary source. Apart from water, which is universally required for the maintenance of homeostasis in mammals, essential nutrients are indispensable for various cellular metabolic processes and for the maintenance and function of tissues and organs. The nutrients considered essential for humans comprise nine amino acids, two fatty acids, thirteen vitamins, fifteen minerals and choline. In addition, there are several molecules that are considered conditionally essential nutrients since they are indispensable in certain developmental and pathological states.

Amino acids

An essential amino acid is an amino acid that is required by an organism but cannot be synthesized de novo by it, and therefore must be supplied in its diet. Out of the twenty standard protein-producing amino acids, nine cannot be endogenously synthesized by humans: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.

Fatty acids

Essential fatty acids (EFAs) are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. Only two fatty acids are known to be essential for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid).

Vitamins and vitamers

Vitamins occur in a variety of related forms known as vitamers. The vitamers of a given vitamin perform the functions of that vitamin and prevent symptoms of deficiency of that vitamin. Vitamins are those essential organic molecules that are not classified as amino acids or fatty acids. They commonly function as enzymatic cofactors, metabolic regulators or antioxidants. Humans require thirteen vitamins in their diet, most of which are actually groups of related molecules (e.g. vitamin E includes tocopherols and tocotrienols): vitamins A, C, D, E, K, thiamine (B₁), riboflavin (B₂), niacin (B₃), pantothenic acid (B₅), pyridoxine (B₆), biotin (B₇), folate (B₉), and cobalamin (B₁₂). The requirement for vitamin D is conditional, as people who get sufficient exposure to ultraviolet light, either from the sun or an artificial source, synthesize vitamin D in the skin.

Minerals

Minerals are the exogenous chemical elements indispensable for life. Although the four elements: carbon, hydrogen, oxygen, and nitrogen (CHON) are essential for life, they are so plentiful in food and drink that these are not considered nutrients and there are no recommended intakes for these as minerals. The need for nitrogen is addressed by requirements set for protein, which is composed of nitrogen-containing amino acids. Sulfur is essential, but again does not have a recommended intake. Instead, recommended intakes are identified for the sulfur-containing amino acids methionine and cysteine.

The essential nutrient trace elements for humans, listed in order of Recommended Dietary Allowance (expressed as a mass), are potassium, chloride, sodium, calcium, phosphorus, magnesium, iron, zinc, manganese, copper, iodine, chromium, molybdenum, and selenium. Additionally, cobalt is a component of Vitamin B₁₂ which is essential. There are other minerals which are essential for some plants and animals, but may or may not be essential for humans, such as boron and silicon.

Choline

Choline is an essential nutrient. The cholines are a family of water-soluble quaternary ammonium compounds. Choline is the parent compound of the cholines class, consisting of ethanolamine having three methyl substituents attached to the amino function. Healthy humans fed artificially composed diets that are deficient in choline develop fatty liver, liver damage, and muscle damage. Choline was not initially classified as essential because the human body can produce choline in small amounts through phosphatidylcholine metabolism.

Conditionally essential

Conditionally essential nutrients are certain organic molecules that can normally be synthesized by an organism, but under certain conditions in insufficient quantities. In humans, such conditions include premature birth, limited nutrient intake, rapid growth, and certain disease states. Inositol, taurine, arginine, glutamine and nucleotides are classified as conditionally essential and are particularly important in neonatal diet and metabolism.

Non-essential

Non-essential nutrients are substances within foods that can have a significant impact on health. Dietary fiber is not absorbed in the human digestive tract. Soluble fiber is metabolized to butyrate and other short-chain fatty acids by bacteria residing in the large intestine. Soluble fiber is marketed as serving a prebiotic function with claims for promoting "healthy" intestinal bacteria.

Non-nutrients

Ethanol (C₂H₅OH) is not an essential nutrient, but it does supply approximately 29 kilojoules (7 kilocalories) of food energy per gram. For spirits (vodka, gin, rum, etc.) a standard serving in the United States is 44 millilitres (1+1⁄2 US fluid ounces), which at 40% ethanol (80 proof) would be 14 grams and 410 kJ (98 kcal). At 50% alcohol, 17.5 g and 513 kJ (122.5 kcal). Wine and beer contain a similar amount of ethanol in servings of 150 and 350 mL (5 and 12 US fl oz), respectively, but these beverages also contribute to food energy intake from components other than ethanol. A 150 mL (5 US fl oz) serving of wine contains 420 to 540 kJ (100 to 130 kcal). A 350 mL (12 US fl oz) serving of beer contains 400 to 840 kJ (95 to 200 kcal).

According to the U.S. Department of Agriculture, based on NHANES 2013–2014 surveys, women ages 20 and up consume on average 6.8 grams of alcohol per day and men consume on average 15.5 grams per day. Ignoring the non-alcohol contribution of those beverages, the average ethanol contributions to daily food energy intake are 200 and 450 kJ (48 and 108 kcal), respectively. Alcoholic beverages are considered empty calorie foods because, while providing energy, they contribute no essential nutrients.

By definition, phytochemicals include all nutritional and non-nutritional components of edible plants. Included as nutritional constituents are provitamin A carotenoids, whereas those without nutrient status are diverse polyphenols, flavonoids, resveratrol, and lignans that are present in numerous plant foods. Some phytochemical compounds are under preliminary research for their potential effects on human diseases and health. However, the qualification for nutrient status of compounds with poorly defined properties in vivo is that they must first be defined with a Dietary Reference Intake level to enable accurate food labeling, a condition not established for most phytochemicals that are claimed to provide antioxidant benefits.

Deficiencies and toxicity

See Vitamin, Mineral (nutrient), Protein (nutrient)

An inadequate amount of a nutrient is a deficiency. Deficiencies can be due to several causes, including an inadequacy in nutrient intake, called a dietary deficiency, or any of several conditions that interfere with the utilization of a nutrient within an organism. Some of the conditions that can interfere with nutrient utilization include problems with nutrient absorption, substances that cause a greater-than-normal need for a nutrient, conditions that cause nutrient destruction, and conditions that cause greater nutrient excretion. Nutrient toxicity occurs when excess consumption of a nutrient does harm to an organism.

In the United States and Canada, recommended dietary intake levels of essential nutrients are based on the minimum level that "will maintain a defined level of nutriture in an individual", a definition somewhat different from that used by the World Health Organization and Food and Agriculture Organization of a "basal requirement to indicate the level of intake needed to prevent pathologically relevant and clinically detectable signs of a dietary inadequacy".

In setting human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or maximum amounts to avoid the risk of toxicity. For example, for vitamin C, recommended intakes range from 40 mg/day in India to 155 mg/day for the European Union. The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins and minerals, PRIs for the European Union (same concept as RDAs), followed by what three government organizations deem to be the safe upper intake. RDAs are set higher than EARs to cover people with higher-than-average needs. Adequate Intakes (AIs) are set when there is insufficient information to establish EARs and RDAs. Countries establish tolerable upper intake levels, also referred to as upper limits (ULs), based on amounts that cause adverse effects. Governments are slow to revise information of this nature. For the U.S. values, except calcium and vitamin D, all data date from 1997 to 2004.

* The daily recommended amounts of niacin and magnesium are higher than the tolerable upper limit because, for both nutrients, the ULs identify the amounts which will not increase risk of adverse effects when the nutrients are consumed as a serving of a dietary supplement. Magnesium supplementation above the UL may cause diarrhea. Supplementation with niacin above the UL may cause flushing of the face and a sensation of body warmth. Each country or regional regulatory agency decides on a safety margin below when symptoms may occur, so the ULs may differ based on source.

EAR U.S. Estimated Average Requirements.

RDA U.S. Recommended Dietary Allowances; higher for adults than for children, and may be even higher for women who are pregnant or lactating.

AI U.S. Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs.

PRI Population Reference Intake is European Union equivalent of RDA; higher for adults than for children, and may be even higher for women who are pregnant or lactating. For Thiamin and Niacin, the PRIs are expressed as amounts per megajoule (239 kilocalories) of food energy consumed.

Upper Limit Tolerable upper intake levels.

ND ULs have not been determined.

NE EARs, PRIs or AIs have not yet been established or will not be (EU does not consider chromium an essential nutrient).

Plant

Plant nutrients consist of more than a dozen minerals absorbed through roots, plus carbon dioxide and oxygen absorbed or released through leaves. All organisms obtain all their nutrients from the surrounding environment.

Plants absorb carbon, hydrogen, and oxygen from air and soil as carbon dioxide and water. Other nutrients are absorbed from soil (exceptions include some parasitic or carnivorous plants). Counting these, there are 17 important nutrients for plants: these are macronutrients; nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), carbon (C), oxygen(O) and hydrogen (H), and the micronutrients; iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo) and nickel (Ni). In addition to carbon, hydrogen, and oxygen, nitrogen, phosphorus, and sulfur are also needed in relatively large quantities. Together, the "Big Six" are the elemental macronutrients for all organisms. They are sourced from inorganic matter (for example, carbon dioxide, water, nitrates, phosphates, sulfates, and diatomic molecules of nitrogen and, especially, oxygen) and organic matter (carbohydrates, lipids, proteins).

See also

• Food composition
• Nutrient cycle
• Nutrient density
• Nutrition
• Nutritionism
• List of macronutrients
• List of micronutrients
• List of nutrition guides
• List of phytochemicals in food
• River Continuum Concept
• Table of food nutrients

References

1. ^ Ensminger AH (1994). Foods & nutrition encyclopedia. CRC Press. pp. 527–. ISBN 978-0-8493-8980-1. Retrieved 12 October 2010.
2. Kern M (12 May 2005). CRC desk reference on sports nutrition. CRC Press. pp. 117–. ISBN 978-0-8493-2273-0. Retrieved 12 October 2010.
3. "31.1C: Essential Nutrients for Plants". Biology LibreTexts. 2018-07-16. Retrieved 2020-08-16.
4. ^ "Composition of Foods Raw, Processed, Prepared USDA National Nutrient Database for Standard Reference, Release 26 Documentation and User Guide" (PDF). USDA. August 2013. p. 14.
5. "Chapter 3: Calculation Of The Energy Content Of Foods – Energy Conversion Factors". Food and Agriculture Organization of the United Nations. Retrieved 30 March 2017.
6. Gernand, A. D; Schulze, K. J; Stewart, C. P; West Jr, K. P; Christian, P (2016). "Micronutrient deficiencies in pregnancy worldwide: Health effects and prevention". Nature Reviews Endocrinology. 12 (5): 274–289. doi:10.1038/nrendo.2016.37. PMC 4927329. PMID 27032981.
7. Tucker, K. L (2016). "Nutrient intake, nutritional status, and cognitive function with aging". Annals of the New York Academy of Sciences. 1367 (1): 38–49. Bibcode:2016NYASA1367...38T. doi:10.1111/nyas.13062. PMID 27116240.
8. "Minerals". Corvallis, OR: Micronutrient Information Center, Linus Pauling Institute, Oregon State University. 2023. Retrieved 18 May 2023.
9. ^ "Vitamins". Corvallis, OR: Micronutrient Information Center, Linus Pauling Institute, Oregon State University. 2023. Retrieved 18 May 2023.
10. "What is an essential nutrient?". NetBiochem Nutrition, University of Utah.
11. Vaughan JG, Geissler C, Nicholson B, Dowle E, Rice E (2009). The new Oxford book of food plants. Oxford University Press US. pp. 212–. ISBN 978-0-19-954946-7. Retrieved 13 October 2010.
12. Jéquier E, Constant F (February 2010). "Water as an essential nutrient: the physiological basis of hydration" (PDF). European Journal of Clinical Nutrition. 64 (2): 115–23. doi:10.1038/ejcn.2009.111. PMID 19724292. S2CID 205129670.
13. ^ Chipponi JX, Bleier JC, Santi MT, Rudman D (May 1982). "Deficiencies of essential and conditionally essential nutrients". The American Journal of Clinical Nutrition. 35 (5 Suppl): 1112–6. doi:10.1093/ajcn/35.5.1112. PMID 6805293.
14. ^ Carver J (2006). "Conditionally essential nutrients: choline, inositol, taurine, arginine, glutamine and nucleotides". In Thureen PJ, Hay WW (eds.). Neonatal Nutrition and Metabolism. Cambridge, UK: Cambridge University Press. pp. 299–311. doi:10.1017/CBO9780511544712.020. ISBN 9780511544712.
15. Kendler BS (2006). "Supplemental conditionally essential nutrients in cardiovascular disease therapy". The Journal of Cardiovascular Nursing. 21 (1): 9–16. doi:10.1097/00005082-200601000-00004. PMID 16407731. S2CID 28748412.
16. Young VR (August 1994). "Adult amino acid requirements: the case for a major revision in current recommendations" (PDF). The Journal of Nutrition. 124 (8 Suppl): 1517S – 1523S. doi:10.1093/jn/124.suppl_8.1517S. PMID 8064412.
17. ^ "Dietary Reference Intakes: The Essential Guide to Nutrient Requirements". Institute of Medicine's Food and Nutrition Board. Archived from the original on 5 July 2014. Retrieved 14 July 2014.
18. Goodhart RS, Shils ME (1980). Modern Nutrition in Health and Disease (6th ed.). Philadelphia: Lea and Febinger. pp. 134–138. ISBN 978-0-8121-0645-9.
19. Ellie W, Rolfes SR (2008). Understanding Nutrition (11th ed.). California: Thomson Wadsworth. p. 154.
20. Brigelius-Flohé R, Traber MG (July 1999). "Vitamin E: function and metabolism". FASEB Journal. 13 (10): 1145–55. doi:10.1096/fasebj.13.10.1145. PMID 10385606. S2CID 7031925.
21. "Vitamin D". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis. 11 February 2021. Retrieved 14 March 2022.
22. "Dietary Intakes of Choline" (PDF). usda.gov. United States Department of Agriculture. Retrieved May 8, 2021.
23. "Choline". nih.gov. National Institutes of Health. Retrieved May 8, 2021.
24. Zeisel, Steven H; da Costa, Kerry-Ann (November 1, 2009). "Choline: an essential nutrient for public health". Nutrition Reviews. 67 (11): 615–623. doi:10.1111/j.1753-4887.2009.00246.x. PMC 2782876. PMID 19906248.
25. Choline. The Metabolomics Innovation Centre, University of Alberta, Edmonton, Canada. 17 August 2016. Retrieved 13 September 2016. {{cite encyclopedia}}: |website= ignored (help)
26. Britannica, The Editors of Encyclopaedia. "choline". Encyclopedia Britannica, 11 Dec. 2013, https://www.britannica.com/science/choline. Accessed 17 February 2022.
27. National Center for Biotechnology Information (2022). PubChem Compound Summary for CID 305, Choline. Retrieved February 17, 2022 from https://pubchem.ncbi.nlm.nih.gov/compound/Choline.
28. "Choline". Micronutrient Information Center. Oregon State University. 28 April 2014. Retrieved May 8, 2021.
29. "High-Fiber Diet - Colon & Rectal Surgery Associates". www.colonrectal.org. Archived from the original on 2020-09-26. Retrieved 2020-08-16.
30. Vital M, Howe AC, Tiedje JM (April 2014). "Revealing the bacterial butyrate synthesis pathways by analyzing (meta)genomic data". mBio. 5 (2): e00889. doi:10.1128/mBio.00889-14. PMC 3994512. PMID 24757212.
31. Lupton JR (February 2004). "Microbial degradation products influence colon cancer risk: the butyrate controversy". The Journal of Nutrition. 134 (2): 479–82. doi:10.1093/jn/134.2.479. PMID 14747692.
32. Cummings JH, Macfarlane GT, Englyst HN (February 2001). "Prebiotic digestion and fermentation". The American Journal of Clinical Nutrition. 73 (2 Suppl): 415S – 420S. doi:10.1093/ajcn/73.2.415s. PMID 11157351.
33. Brownawell AM, Caers W, Gibson GR, Kendall CW, Lewis KD, Ringel Y, Slavin JL (May 2012). "Prebiotics and the health benefits of fiber: current regulatory status, future research, and goals". The Journal of Nutrition. 142 (5): 962–74. doi:10.3945/jn.112.158147. PMID 22457389.
34. ^ Lieber CS (29 September 2004). "Relationships between nutrition, alcohol use, and liver disease". Alcohol Research & Health. 27 (3): 220–31. PMC 6668875. PMID 15535450. Retrieved 2 January 2020.
35. ""What We Eat in America, NHANES 2013-2014"" (PDF).
36. ^ "Phytochemicals". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. February 2016. Retrieved 31 December 2017.
37. ^ "Carotenoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. August 2016. Retrieved 31 December 2017.
38. ^ "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. February 2016. Retrieved 31 December 2017.
39. "Nutrient content claims--general principles; 21CFR101.13". US Food and Drug Administration. 1 April 2017. Retrieved 31 December 2017.
40. Gross P (1 March 2009). "New Roles for Polyphenols. A 3-Part Report on Current Regulations and the State of Science". Nutraceuticals World.
41. Campbell TC, Allison RG, Fisher KD (June 1981). "Nutrient toxicity". Nutrition Reviews. 39 (6): 249–56. doi:10.1111/j.1753-4887.1981.tb07453.x. PMID 7312225.
42. Panel on Dietary Antioxidants and Related Compounds (2017). "Introduction to Dietary Reference Intakes. What are dietary reference intakes?". Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Institute of Medicine, US National Academies of Science. pp. 21–22. doi:10.17226/9810. ISBN 978-0-309-06935-9. PMID 25077263. Retrieved 31 December 2017.
43. ^ "Dietary Reference Intakes (DRIs)" (PDF). Food and Nutrition Board, Institute of Medicine, National Academies. Archived from the original (PDF) on 11 September 2018.
44. ^ Tolerable Upper Intake Levels For Vitamins And Minerals (PDF), European Food Safety Authority, 2006
45. ^ Dietary Reference Intakes for Japanese (2010) National Institute of Health and Nutrition, Japan
46. "Nutrient Requirements and Recommended Dietary Allowances for Indians: A Report of the Expert Group of the Indian Council of Medical Research. pp.283-295 (2009)" (PDF). Archived from the original (PDF) on 15 June 2016. Retrieved 31 December 2017.
47. ^ "Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies" (PDF). 2017. Archived (PDF) from the original on 28 August 2017.
48. Whitney, Elanor and Sharon Rolfes. 2005. Understanding Nutrition, 10th edition, p. 6. Thomson-Wadsworth.
49. Sizer F, Whitney E (12 November 2007). Nutrition: Concepts and Controversies. Cengage Learning. pp. 26–. ISBN 978-0-495-39065-7. Retrieved 12 October 2010.
50. Jones JB (1998). Plant nutrition manual. CRC Press. pp. 34–. ISBN 978-1-884015-31-1. Retrieved 14 October 2010.
51. Barker AV, Pilbeam DJ (2007). Handbook of plant nutrition. CRC Press. ISBN 978-0-8247-5904-9. Retrieved 17 August 2010.
52. New Link in Chain of Life, Wall Street Journal, 2010-12-03, accessed 5 December 2010. "Until now, however, they were all thought to share the same biochemistry, based on the Big Six, to build proteins, fats, and DNA."

External links

• USDA. Dietary Reference Intakes

• Chemical oceanography
• Ecology
• Nutrients
• Edaphology
• Biology and pharmacology of chemical elements
• Nutrition
• Essential nutrients