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 to 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.
Essential versus non-essential definitions of nutrients depends on the organism. Ascorbic acid (vitamin C) is essential, meaning it must be consumed in sufficient amounts by humans and some other animal species, but not by all animals and not by plants, which are able to synthesize it. Inorganic or organic nutrients are classified according to the organism. Inorganic implies minerals, such as iron, selenium, and zinc, while organic describes energy-providing compounds plus vitamins and minerals not processed for energy, but essential for metabolic and genetic functions of DNA, RNA, enzymes, and other molecules.
A classification used primarily for describing nutrient needs by animals divides nutrients into macronutrients and micronutrients. Consumed in relatively large amounts (grams or ounces), macronutrients (carbohydrates, fats, proteins, water) are used primarily for generating energy or incorporation into tissues for growth and repair. Needed in smaller amounts (milligrams or micrograms), micronutrients 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 deficiency outcomes and provide macronutrient and micronutrient guides for both minimal and upper limits of intake. In many countries, macronutrients and micronutrients in significant content are required under regulation for display on food product labels. Nutrients in excess of need may have harmful effects.[1] In edible plants are thousands of compounds generally called phytochemicals with unknown effects on disease or health, including a diverse class with non-nutrient status called polyphenols which remain poorly understood as of 2017.
Plant nutrients consist of more than a dozen minerals absorbed through roots, plus carbon dioxide and oxygen absorbed or released through leaves. For all organisms and all nutrients, the source of nutrients is the surrounding environment.[2][3]
Types of nutrient
Macronutrients
Macronutrients are defined in several ways.[4]
- The chemical elements humans consume in the largest quantities are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, summarized as CHNOPS.
- The molecules that humans consume in the largest quantities via the diet and that provide bulk energy are classified as carbohydrates, proteins, and fats. Water must be consumed in large quantities.
- Calcium, salt (sodium and chloride), magnesium, and potassium (along with phosphorus and sulfur) are among the list of macronutrients because they are required in large quantities compared to micronutrients, such as vitamins and 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 acids are 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 supplies calories. For spirits (vodka, gin, rum, etc.) a standard serving in the United States is 1.5 US fluid ounces (44 ml), which at 40% ethanol (80 proof) would be 14 grams and 98 calories. At 50% alcohol, 17.5 grams and 122.5 calories. Wine and beer contain a similar range of ethanol for servings of 5 US fluid ounces (150 ml) and 12 US fluid ounces (350 ml), respectively, but these beverages also contain non-ethanol calories. A 5-ounce serving of wine contains 100 to 130 calories. A 12-ounce serving of beer contains 95 to 200 calories.[citation needed] 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.[5] Ignoring the non-alcohol contribution of those beverages, the average ethanol calorie contributions are 48 and 108 cal/day, respectively.[citation needed] Alcoholic beverages are considered empty calorie foods because, other than calories, they contribute no essential nutrients.
Fat has an energy content of 9 kcal/g (~37.7 kJ/g); proteins and carbohydrates 4 kcal/g (~16.7 kJ/g); ethanol 7 kcal/g (~29.3 kJ/g).[citation needed]
Micronutrients
Micronutrients support metabolism.
- Dietary minerals are generally trace elements, salts, or ions such as copper and iron. Some of these minerals are essential to human metabolism.
- Vitamins are organic compounds essential to the body. They usually act as coenzymes or cofactors for various proteins in the body.
- Water is an essential nutrient and is the solvent in which all the chemical reactions of life take place.
Plant nutrition
Plants absorb nutrients from the soil, the atmosphere, and from water for aquatic plants. An exception are the carnivorous plants, which externally digest nutrients from animals before absorbing them for nutrients.[6]
The chemical elements consumed in the greatest quantities by plants are carbon, hydrogen, and oxygen. These are present in the environment in the form of water and carbon dioxide; energy is provided by sunlight.[7] Nitrogen, phosphorus, and sulfur are also needed in relatively large quantities. Together, the "Big Six", often represented by the acronym CHNOPS[8], are the elemental macronutrients for all organisms.[9] Usually they are sourced from inorganic (for example, carbon dioxide, water, nitrate, phosphate, sulfate) or organic (carbohydrates, lipids, proteins) compounds, although elemental diatomic molecules of nitrogen and, especially, oxygen are often used.
Other chemical elements are also necessary to carry out various life processes and build structures; see fertilizer and micronutrient for more information.
Some of these are considered micronutrients in certain organisms. The mnemonic C. HOPKN'S CaFe Mg (to be said as "C. Hopkins coffee mug") is used by some students to remember the list as: carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, and magnesium. Silicon, chloride, sodium, copper, zinc, and molybdenum are sometimes also included, but are in other cases considered micronutrients.[10]
Essentiality
Essential nutrients
An essential nutrients 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.[11][12] Apart from water, which is universally required the maintenance of homeostasis in mammals,[13] essential nutrients are indispensable for various cellular metabolic processes and maintaining tissue and organ function.[14] In the case of humans, there are nine amino acids, two fatty acids, thirteen vitamins and fifteen minerals that are considered essential nutrients.[14] In addition, there are several molecules that are considered conditionally essential nutrients since they are indispensable in certain developmental and pathological states.[14][15][16]
Amino acids
An essential amino acid is an amino acid that cannot be synthesized de novo by an organism, 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.[17][18]
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.[19] 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).[20]
Vitamins
Vitamins are organic molecules essential for an organism 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).[21]
Minerals
Minerals are the exogenous chemical elements indispensable for an organism which are not provided by the other essential nutrients. The elements provided by essential amino acids, fatty acids and vitamins are carbon, hydrogen, oxygen, nitrogen and sulfur. For humans, the "major minerals" are calcium, phosphorus, potassium, sodium, chlorine, and magnesium. "Minor minerals" include metals such as iron, zinc, manganese and copper.
Conditionally essential nutrients
Conditionally essential nutrients are certain organic molecules that can normally be synthesized by an organism, but under certain conditions such biosynthesis is not enough to prevent a deficiency syndrome. In humans, such conditions include prematurity, limited nutrient intake, rapid growth, and certain disease states.[15] Choline, inositol, taurine, arginine, glutamine and nucleotides are classified as conditionally essential and are particularly important in neonatal diet and metabolism.[15]
Non-essential nutrients
Non-essential nutrients are substances within foods that can have a significant impact on health; these substances can be beneficial or toxic. For example, dietary fiber is not absorbed in the human digestive tract, but is important in maintaining the bulk of a bowel movement to avoid constipation. A subset of dietary fiber, known as soluble fiber, can be metabolized by bacteria residing in the large intestine. Soluble fiber is marketed as serving a prebiotic function – promoting "healthy" intestinal bacteria. Bacterial metabolism of soluble fiber is also thought to product short-chain fatty acids, which may be absorbed into intestinal cells as a source of calories.[citation needed]
Non-nutrients
By definition, phytochemicals include all nutritional and non-nutritional components in edible plants.[22] Included as nutritional constituents are provitamin A carotenoids,[23] whereas those without nutrient status are diverse polyphenols, flavonoids, resveratrol, and lignans – often claimed to have antioxidant effects – that are present in numerous plant foods.[24] Many non-nutrient compounds are under preliminary research for their potential effects on human diseases and health, but there is no evidence as of 2017 that they have any effects in humans.[24] Further, 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,[25] a condition not established for most phytochemicals incorrectly asserted as antioxidant nutrients.[26]
Deficiencies and toxicity
See Vitamin, Mineral (nutrient), Protein (nutrient)
An inadequate amount of a nutrient is a deficiency. Deficiencies can be due to a number of 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.[1] 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.[1] Nutrient toxicity occurs when excess consumption of a nutrient does harm to an organism.[27]
For human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or to not risk toxicity.[28][29][30] For example, for vitamin C, recommended intakes range from 40 mg/day in India[31] to 110 mg/day for the European Union.[32]
For the United States and Canada, recommended dietary intake levels of essential nutrients are based on the minimal level that "will maintain a defined level of nutriture in an individual", a definition somewhat different than used by the World Health Organization and Food and Agriculture Organization as a "basal requirement to indicate the level of intake needed to prevent pathologically relevant and clinically detectable signs of a dietary inadequacy".[33] The table below shows U.S. Estimated Average Requirements and Recommended Dietary Allowances for vitamins and minerals, followed by what three government organizations deem to be the safe upper intake. Governments are slow to revise information of this nature. For the U.S. values, with the exception of calcium and vitamin D, all of the data date to 1997-2004.[18]
Nutrient | U.S. EAR[28] | Highest U.S. RDA or AI[28] |
U.S. UL[28] | EU UL[29] | Japan UL[30] | Unit |
---|---|---|---|---|---|---|
Vitamin A | 625 | 900 | 3000 | 3000 | 2700 | µg |
Vitamin C | 75 | 90 | 2000 | ND | ND | mg |
Vitamin D | 10 | 15 | 100 | 100 | 100 | µg |
Vitamin K | NE | 120 | ND | ND | ND | µg |
α-tocopherol (Vit E) | 12 | 15 | 1000 | 300 | 650-900 | mg |
Thiamin (Vit B1) | 1.0 | 1.2 | ND | ND | ND | mg |
Riboflavin (Vit B2) | 1.1 | 1.3 | ND | ND | ND | mg |
Niacin (Vit B3) | 12 | 16 | 35 | 10 | 60-85 | mg |
Pantothenic acid (Vit B5) | NE | 5 | ND | ND | ND | mg |
Vitamin B6 | 1.1 | 1.3 | 100 | 25 | 40-60 | mg |
Biotin (Vit B7) | NE | 30 | ND | ND | ND | µg |
Folate (Vit B9) | 320 | 400 | 1000 | 1000 | 900-1000 | µg |
Cyanocobalamin (Vit B12) | 2.0 | 2.4 | ND | ND | ND | µg |
Choline | NE | 550 | 3500 | ____ | ____ | mg |
Calcium | 800 | 1000 | 2500 | 2500 | 2500 | mg |
Chloride | NE | 2300 | 3600 | ND | ND | mg |
Chromium | NE | 35 | ND | ND | ND | µg |
Copper | 700 | 900 | 10000 | 5000 | 10000 | µg |
Fluoride | NE | 4 | 10 | 7 | __ | mg |
Iodine | 95 | 150 | 1100 | 600 | 3000 | µg |
Iron | 6 | 18 (females) 8 (males) |
45 | ND | 40-45 | mg |
Magnesium | 350 | 420 | 350 | 250 | 350 | mg |
Manganese | NE | 2.3 | 11 | ND | 11 | mg |
Molybdenum | 34 | 45 | 2000 | 600 | 450-550 | µg |
Phosphorus | 580 | 700 | 4000 | ND | 3000 | mg |
Potassium | NE | 4700 | ND | ND | 2700-3000 | mg |
Selenium | 45 | 55 | 400 | 300 | 330-460 | µg |
Sodium | NE | 1500 | 2300 | ND | 3000-3600 | mg |
Zinc | 9.4 | 11 | 40 | 25 | 35-45 | mg |
- EAR U.S. Estimated Average Requirements
- RDA U.S. Recommended Dietary Allowances
- AI U.S. Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs
- UL Tolerable upper intake levels
- ND ULs have not been determined
- NE EARs have not yet been established or not yet evaluated
See also
References
- ^ a b c Audrey H. Ensminger (1994). Foods & nutrition encyclopedia. CRC Press. pp. 527–. ISBN 978-0-8493-8980-1. Retrieved 12 October 2010.
- ^ Whitney, Elanor and Sharon Rolfes. 2005. Understanding Nutrition, 10th edition, p. 6. Thomson-Wadsworth.
- ^ FRANCES SIZER; ELLIE WHITNEY (12 November 2007). NUTRITION: CONCEPTS AND CONTROVERSIES. Cengage Learning. pp. 26–. ISBN 978-0-495-39065-7. Retrieved 12 October 2010.
- ^ Mark Kern (12 May 2005). CRC desk reference on sports nutrition. CRC Press. pp. 117–. ISBN 978-0-8493-2273-0. Retrieved 12 October 2010.
- ^ "What We Eat in America, NHANES 2013-2014"
- ^ David Sadava; H. Craig Heller; David M. Hillis; May Berenbaum (2009). Life: The Science of Biology. Macmillan. pp. 767–. ISBN 978-1-4292-1962-4. Retrieved 12 October 2010.
- ^ J. Benton Jones (1998). Plant nutrition manual. CRC Press. pp. 34–. ISBN 978-1-884015-31-1. Retrieved 14 October 2010.
- ^ CHNOPS: The Six Most Abundant Elements of Life, Pearson BioCoach, 2010, accessed 2010-12-09. "Most biological molecules are made from covalent combinations of six important elements, whose chemical symbols are CHNOPS. ... Although more than 25 types of elements can be found in biomolecules, six elements are most common. These are called the CHNOPS elements; the letters stand for the chemical abbreviations of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur."
- ^ New Link in Chain of Life, Wall Street Journal, 2010-12-03, accessed 2010-12-05. "Until now, however, they were all thought to share the same biochemistry, based on the Big Six, to build proteins, fats and DNA."
- ^ Perry, David A (1994). Forest ecosystems. Baltimore: Johns Hopkins University Press. ISBN 978-0-8018-4987-9.
- ^ "What is an essential nutrient?". NetBiochem Nutrition, University of Utah.
- ^ John Griffith Vaughan; Catherine Geissler; Barbara Nicholson; Elisabeth Dowle; Elizabeth Rice (2009). The new Oxford book of food plants. Oxford University Press US. pp. 212–. ISBN 978-0-19-954946-7. Retrieved 13 October 2010.
- ^ Jéquier, E; Constant, F (2 September 2009). "Water as an essential nutrient: the physiological basis of hydration". European Journal of Clinical Nutrition. 64 (2): 115–123. doi:10.1038/ejcn.2009.111.
- ^ a b c Chipponi, JX; Bleier, JC; Santi, MT; Rudman, D (May 1982). "Deficiencies of essential and conditionally essential nutrients". American Journal of Clinical Nutrition. 35 (5 Suppl): 1112–1116. PMID 6805293.
- ^ a b c Carver, Jane (2006). "Conditionally essential nutrients: choline, inositol, taurine, arginine, glutamine and nucleotides". Neonatal Nutrition and Metabolism. Cambridge, UK: Cambridge University Press. pp. 299–311.
- ^ Kendler, BS (2006). "Supplemental conditionally essential nutrients in cardiovascular disease therapy". Journal of Cardiovascular Nursing. 21 (1): 9–16. PMID 16407731.
- ^ Young VR (1994). "Adult amino acid requirements: the case for a major revision in current recommendations" (PDF). J. Nutr. 124 (8 Suppl): 1517S–1523S. PMID 8064412.
- ^ a b Dietary Reference Intakes: The Essential Guide to Nutrient Requirements, published by the Institute of Medicine's Food and Nutrition Board, currently available online at "Archived copy". Archived from the original on 2014-07-05. Retrieved 2014-07-14.
{{cite web}}
: Unknown parameter|deadurl=
ignored (|url-status=
suggested) (help)CS1 maint: archived copy as title (link) - ^ Robert S. Goodhart; Maurice E. Shils (1980). Modern Nutrition in Health and Disease (6th ed.). Philadelphia: Lea and Febinger. pp. 134–138. ISBN 0-8121-0645-8.
- ^ Whitney Ellie; Rolfes SR (2008). Understanding Nutrition (11th ed.). California: Thomson Wadsworth. p. 154.
- ^ Brigelius-Flohé R, Traber MG; Traber (1999). "Vitamin E: function and metabolism". FASEB J. 13 (10): 1145–1155. PMID 10385606.
- ^ "Phytochemicals". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. February 2016. Retrieved 31 December 2017.
- ^ "Carotenoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. August 2016. Retrieved 31 December 2017.
- ^ a b "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. February 2016. Retrieved 31 December 2017.
- ^ "Nutrient content claims--general principles; 21CFR101.13". US Food and Drug Administration. 1 April 2017. Retrieved 31 December 2017.
- ^ Gross, Paul (March 1, 2009). "New Roles for Polyphenols. A 3-Part Report on Current Regulations and the State of Science". Nutraceuticals World.
- ^ "Nutrient Toxicity". Nutrition Reviews. 39 (6): 249–256. 2009. doi:10.1111/j.1753-4887.1981.tb07453.x.
- ^ a b c d Dietary Reference Intakes (DRIs) Food and Nutrition Board, Institute of Medicine, National Academies
- ^ a b Tolerable Upper Intake Levels For Vitamins And Minerals (PDF), European Food Safety Authority, 2006
- ^ a b Dietary Reference Intakes for Japanese (2010) National Institute of Health and Nutrition, Japan
- ^ "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 June 15, 2016.
{{cite web}}
: Unknown parameter|deadurl=
ignored (|url-status=
suggested) (help) - ^ "Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies" (PDF). 2017. Archived from the original (PDF) on August 28, 2017.
{{cite web}}
: Unknown parameter|deadurl=
ignored (|url-status=
suggested) (help) - ^ "Introduction to Dietary Reference Intakes. What are dietary reference intakes? (Chapter 1, page 21-22)". Institute of Medicine, US National Academies of Science. 2017. Retrieved 31 December 2017.