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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.


Different types of organism have different essential nutrients. Ascorbic acid (vitamin C) is essential, meaning it must be consumed in sufficient amounts, to humans and some other animal species, but not to all animals and not to plants, which 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, among many others, energy-providing compounds 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 used primarily 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 deficiency outcomes[ clarification needed ] and provide macronutrient and micronutrient guides for both lower and upper limits of intake. In many countries, macronutrients and micronutrients in significant content[ clarification needed ] are required by regulations to be displayed on food product labels. Nutrients in larger quantities than the body needs may have harmful effects. [1] 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 2017.



Macronutrients are defined in several ways. [2]

Macronutrients provide energy:

Fat has an energy content of 9  kcal/g (~37.7 kJ/g) and proteins and carbohydrates 4 kcal/g (~16.7 kJ/g).[ citation needed ]


Micronutrients support metabolism.



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. [3] [4] Apart from water, which is universally required for the maintenance of homeostasis in mammals, [5] essential nutrients are indispensable for various cellular metabolic processes and; for the maintenance and function of tissues and organs. [6] In the case of humans, there are nine amino acids, two fatty acids, thirteen vitamins and fifteen minerals that are considered essential nutrients. [6] In addition, there are several molecules that are considered conditionally essential nutrients since they are indispensable in certain developmental and pathological states. [6] [7] [8]

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. [9] [10]

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. [11] 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). [12]


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): [13] vitamins A, C, D, E, K, thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B6 (e.g., pyridoxine), 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 are the exogenous chemical elements indispensable for life. Although the four elements: carbon, hydrogen, oxygen, and nitrogen, 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 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, selenium and cobalt (the last as a component of vitamin B12). 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.

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. [7] Choline, inositol, taurine, arginine, glutamine and nucleotides are classified as conditionally essential and are particularly important in neonatal diet and metabolism. [7]


Non-essential nutrients are substances within foods that can have a significant impact on health. Insoluble dietary fiber is not absorbed in the human digestive tract, but is important in maintaining the bulk of a bowel movement to avoid constipation.[ medical citation needed ] Soluble fiber can be metabolized by bacteria residing in the large intestine. [14] [15] [16] Soluble fiber is marketed as serving a prebiotic function with claims for promoting "healthy" intestinal bacteria. [17] Bacterial metabolism of soluble fiber also produces short-chain fatty acids like butyric acid, which may be absorbed into intestinal cells as a source of calories. [14] [15] [16]


Ethanol (C2H5OH) is not an essential nutrient, but it does supply approximately 7 calories per gram. [18] [19] 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 amount of ethanol in 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. [19] 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. [20] Ignoring the non-alcohol contribution of those beverages, the average ethanol calorie contributions are 48 and 108 cal/day, respectively. Alcoholic beverages are considered empty calorie foods because, while providing calories, they contribute no essential nutrients. [18]

By definition, phytochemicals include all nutritional and non-nutritional components of edible plants. [21] Included as nutritional constituents are provitamin A carotenoids, [22] 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. [23] A number of phytochemical compounds are under preliminary research for their potential effects on human diseases and health. [21] [22] [23] 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, [24] a condition not established for most phytochemicals that are claimed to be antioxidant nutrients. [25]

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. [26]

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". [27]

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. [28] [29] [30] For example, for vitamin C, recommended intakes range from 40 mg/day in India [31] to 155 mg/day for the European Union. [32] 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 not sufficient information to establish EARs and RDAs. 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. [10]

NutrientU.S. EAR [28] Highest U.S.
RDA or AI [28]
Highest EU
PRI or AI [32]
Upper limitUnit
U.S. [28] EU [29] Japan [30]
Vitamin A 6259001300300030002700µg
Vitamin C 75901552000NDNDmg
Vitamin D 101515100100100µg
Vitamin K NE12070NDNDNDµg
α-tocopherol (Vit E)1215131000300650-900mg
Thiamin (Vit B1) mg/MJNDNDNDmg
Riboflavin (Vit B2)
Niacin* (Vit B3)12161.6 mg/MJ351060-85mg
Pantothenic acid (Vit B5)NE57NDNDNDmg
Vitamin B6
Biotin (Vit B7)NE3045NDNDNDµg
Folate (Vit B9)32040060010001000900-1000µg
Cobalamin (Vit B12)µg
Choline NE5505203500NDNDmg
Calcium 80010001000250025002500mg
Chloride NE2300NE3600NDNDmg
Chromium NE35NENDNDNDµg
Copper 700900160010000500010000µg
Fluoride NE43.4107____mg
Iodine 9515020011006003000µg
Iron 618 (females)
8 (males)
16 (females)
11 (males)
Manganese NE2.33.011ND11mg
Molybdenum 3445652000600450-550µg
Phosphorus 5807006404000ND3000mg
Potassium NE47004000NDND2700-3000mg
Selenium 455570400300330-460µg
Sodium NE1500NE2300ND3000-3600mg
Zinc 9.41116.3402535-45mg

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 MJ of calories consumed. MJ = megajoule = 239 food calories.

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 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. [33] [34]

Plants absorb carbon, hydrogen and oxygen from air and soil in the form of carbon dioxide and water. [35] Other nutrients are absorbed from soil (exceptions include some parasitic or carnivorous plants). Counting these, there are 17 important nutrients for plants: [36] 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. [37] 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

Related Research Articles

Carbohydrate Organic compound that consists only of carbon, hydrogen, and oxygen

A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may be different from n). This formula holds true for monosaccharides. Some exceptions exist; for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. The carbohydrates are technically hydrates of carbon; structurally it is more accurate to view them as aldoses and ketoses.

Nutrition is the science that interprets the nutrients and other substances in food in relation to maintenance, growth, reproduction, health and disease of an organism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion.

Vitamin Nutrients required by organisms in small amounts

A vitamin is an organic molecule (or related set of molecules) that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrients cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet. Vitamin C can be synthesized by some species but not by others; it is not a vitamin in the first instance but is in the second. The term vitamin does not include the three other groups of essential nutrients: minerals, essential fatty acids, and essential amino acids. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, vitamin E consists of four tocopherols and four tocotrienols. Though some sources list fourteen by including choline, major health organizations list thirteen: vitamin A (as all-trans-retinol, all-trans-retinyl-esters, as well as all-trans-beta-carotene and other provitamin A carotenoids), vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B7 (biotin), vitamin B9 (folic acid or folate), vitamin B12 (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones).

Pantothenic acid chemical compound

Pantothenic acid, also called vitamin B5 (a B vitamin), is a water-soluble vitamin. Pantothenic acid is an essential nutrient. Animals require pantothenic acid in order to synthesize coenzyme-A (CoA), as well as to synthesize and metabolize proteins, carbohydrates, and fats. The anion is called pantothenate.

Biotin chemical compound

Biotin also called vitamin H (the H represents Haar und Haut, German words for "hair and skin"), vitamin B7 or vitamin B8 (in many countries like France, where vitamin B7 is used for Inositol) is a water-soluble B vitamin. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids.

Isoleucine is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, an α-carboxylic acid group, and a hydrocarbon side chain with a branch. It is classified as a non-polar, uncharged, branched-chain, aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it, and must be ingested in our diet. Isoleucine is synthesized from pyruvate employing leucine biosynthesis enzymes in other organisms such as bacteria. It is encoded by the codons AUU, AUC, and AUA.

Human nutrition provision of essential nutrients necessary to support human life and health

Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and health. Poor nutrition is a chronic problem often linked to poverty, food security or a poor understanding of nutrition and dietary practices. Malnutrition and its consequences are large contributors to deaths and disabilities worldwide. Good nutrition is necessary for children to grow physically, and for normal human biological development.

An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized de novo by the organism at a rate commensurate with its demand, and thus must be supplied in its diet. Of the 21 amino acids common to all life forms, the nine amino acids humans cannot synthesize are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.

Dietary supplement Product that provides additional source of nutrients

A dietary supplement is a manufactured product intended to supplement the diet when taken by mouth as a pill, capsule, tablet, or liquid. A supplement can provide nutrients either extracted from food sources or synthetic, individually or in combination, in order to increase the quantity of their consumption. The class of nutrient compounds includes vitamins, minerals, fiber, fatty acids and amino acids. Dietary supplements can also contain substances that have not been confirmed as being essential to life, but are marketed as having a beneficial biological effect, such as plant pigments or polyphenols. Animals can also be a source of supplement ingredients, as for example collagen from chickens or fish. These are also sold individually and in combination, and may be combined with nutrient ingredients. In the United States and Canada, dietary supplements are considered a subset of foods, and are regulated accordingly. The European Commission has also established harmonized rules to help insure that food supplements are safe and properly labeled.

In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight, are usually not included in lists of major nutrient minerals. These four elements compose about 96% of the weight of the human body, and major minerals (macrominerals) and minor minerals compose the remainder.

The Dietary Reference Intake (DRI) is a system of nutrition recommendations from the Institute of Medicine (IOM) of the National Academies. It was introduced in 1997 in order to broaden the existing guidelines known as Recommended Dietary Allowances. The DRI values differ from those used in nutrition labeling on food and dietary supplement products in the U.S. and Canada, which uses Reference Daily Intakes (RDIs) and Daily Values (%DV) which were based on outdated RDAs from 1968 but were updated as of 2016.

Cat food food for consumption by cats

Cat food is food for consumption by cats. Cats have specific requirements for their dietary nutrients. Certain nutrients, including many vitamins and amino acids, are degraded by the temperatures, pressures and chemical treatments used during manufacture, and hence must be added after manufacture to avoid nutritional deficiency.

Micronutrients are essential elements required by organisms in varying quantities throughout life to orchestrate a range of physiological functions to maintain health. Micronutrient requirements differ between organisms; for example, humans and other animals require numerous vitamins and dietary minerals, whereas plants require specific minerals. For human nutrition, micronutrient requirements are in amounts generally less than 100 milligrams per day, whereas macronutrients are required in gram quantities daily.

Empty calories foods lacking nutritional value

In human nutrition, the term empty calories applies to foods and beverages composed primarily or solely of sugar, fats or oils, or alcohol-containing beverages. These supply food energy but little to no other nutrition in the way of vitamins, minerals, protein, fibre, or essential fatty acids. Fat contributes nine calories per gram, ethanol seven calories, sugar four calories. The U.S. Department of Agriculture (USDA) advises, "A small amount of empty calories is okay, but most people eat far more than is healthy." The phrase is derived from low nutrient density, which is the proportion of nutrients in a food relative to its energy content.

Protein (nutrient) nutrient for the human body

Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue and can also serve as a fuel source. As a fuel, proteins provide as much energy density as carbohydrates: 4 kcal per gram; in contrast, lipids provide 9 kcal per gram. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition.

Low-fat diet

A low-fat diet is one that restricts fat, and often saturated fat and cholesterol as well. Low-fat diets are intended to reduce the occurrence of conditions such as heart disease and obesity. For weight loss, they perform similarly to a low-carbohydrate diet, since macronutrient composition does not determine weight loss success. Fat provides nine calories per gram while carbohydrates and protein each provide four calories per gram. The Institute of Medicine recommends limiting fat intake to 35% of total calories to control saturated fat intake.

Animal nutrition focuses on the dietary nutrients needs of animals, primarily those in agriculture and food production, but also in zoo's, aquariums, and wildlife management.

Vegan nutrition fiber content of foods

Vegan nutrition refers to the nutritional and human health aspects of vegan diets. A well-planned, balanced vegan diet is suitable to meet all recommendations for nutrients in every stage of human life. Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamin C, vitamin E, iron, and phytochemicals; and lower in dietary energy, saturated fat, cholesterol, long-chain omega-3 fatty acids, vitamin D, calcium, zinc, and vitamin B12. Preliminary evidence from epidemiological research indicates that a vegan diet may lower the risk of cancer.

Like the human practice of veganism, vegan dog foods are those formulated with the exclusion of ingredients that contain or were processed with any part of an animal, or any animal byproduct. Vegan dog food may incorporate the use of fruits, vegetables, cereals, legumes, nuts, vegetable oils, and soya, as well as any other non-animal based foods. The omnivorous domestic canine has evolved to metabolize carbohydrates and thrive on a diet lower in protein, and therefore, a vegan diet may be substantial if properly formulated and balanced.


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