This is an accepted version of this page
108-396: Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security , or a poor understanding of nutritional requirements. Malnutrition and its consequences are large contributors to deaths, physical deformities, and disabilities worldwide. Good nutrition
216-411: A catalytic role in enzymes . Some trace mineral elements (RDA < 200 mg/day) are, in alphabetical order: Ultratrace minerals are an as yet unproven aspect of human nutrition, and may be required at amounts measured in very low ranges of μg/day. Many ultratrace elements have been suggested as essential, but such claims have usually not been confirmed. Definitive evidence for efficacy comes from
324-416: A glycerol backbone. Some fatty acids, but not all, are essential in the diet: they cannot be synthesized in the body. Protein molecules contain nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental components of protein are nitrogen-containing amino acids , some of which are essential in the sense that humans cannot make them internally. Some of the amino acids can be converted (with
432-468: A glycerol . They are typically found as triglycerides (three fatty acids attached to one glycerol backbone). Fats may be classified as saturated or unsaturated depending on the chemical structure of the fatty acids involved. Saturated fats have all of the carbon atoms in their fatty acid chains bonded to hydrogen atoms , whereas unsaturated fats have some of these carbon atoms double-bonded , so their molecules have relatively fewer hydrogen atoms than
540-416: A hemiacetal or hemiketal group, depending on whether the linear form was an aldose or a ketose. The reaction is easily reversed, yielding the original open-chain form. In these cyclic forms, the ring usually has five or six atoms. These forms are called furanoses and pyranoses , respectively—by analogy with furan and pyran , the simplest compounds with the same carbon-oxygen ring (although they lack
648-446: A sweet taste . Most monosaccharides have the formula (CH 2 O) x (though not all molecules with this formula are monosaccharides). Examples of monosaccharides include glucose (dextrose), fructose (levulose), and galactose . Monosaccharides are the building blocks of disaccharides (such as sucrose , lactose and maltose ) and polysaccharides (such as cellulose and starch ). The table sugar used in everyday vernacular
756-579: A building block for series 1 prostaglandins (e.g. anti-inflammatory PGE1), whereas arachidonic acid (AA) serves as a building block for series 2 prostaglandins (e.g. pro-inflammatory PGE 2). Both DGLA and AA can be made from the omega-6 linoleic acid (LA) in the human body, or can be taken in directly through food. An appropriately balanced intake of omega-3 and omega-6 partly determines the relative production of different prostaglandins . In industrialized societies, people typically consume large amounts of processed vegetable oils, which have reduced amounts of
864-433: A carbonyl −(C=O)− between two carbons; then it is formally a ketone, and is termed a ketose. Ketoses of biological interest usually have the carbonyl at position 2. The various classifications above can be combined, resulting in names such as "aldohexose" and "ketotriose". A more general nomenclature for open-chain monosaccharides combines a Greek prefix to indicate the number of carbons (tri-, tetr-, pent-, hex-, etc.) with
972-435: A class of eicosanoids known as prostaglandins , which have roles throughout the human body. The omega-3 eicosapentaenoic acid (EPA), which can be made in the human body from the omega-3 essential fatty acid alpha-linolenic acid (ALA), or taken in through marine food sources, serves as a building block for series 3 prostaglandins (e.g., weakly inflammatory PGE3). The omega-6 dihomo-gamma-linolenic acid (DGLA) serves as
1080-510: 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
1188-593: 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
SECTION 10
#17328008043611296-597: 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
1404-435: A framework for ensuring adequate nutrition. DRVs are categorized into three main types: Reference Nutrient Intake (RNI), which covers the nutritional needs of 95% of the population; Estimated Average Requirement (EAR), meeting the needs of 50%; and Lower Recommended Nutritional Intake (LRNI), which addresses the requirements of 5% of the population. These categories help to tailor dietary recommendations to different segments of
1512-660: A human does not need to eat carbohydrates. Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Monosaccharides include glucose , fructose and galactose . Disaccharides include sucrose , lactose , and maltose ; purified sucrose , for instance, is used as table sugar. Polysaccharides, which include starch and glycogen , are often referred to as 'complex' carbohydrates because they are typically long multiple-branched chains of sugar units. Traditionally, simple carbohydrates were believed to be absorbed quickly, and therefore raise blood-glucose levels more rapidly than complex carbohydrates. This
1620-401: A left and a right glove). Monosaccharides with four or more carbons may contain multiple chiral carbons, so they typically have more than two stereoisomers. The number of distinct stereoisomers with the same diagram is bounded by 2 , where c is the total number of chiral carbons. The Fischer projection is a systematic way of drawing the skeletal formula of an acyclic monosaccharide so that
1728-427: A linear and unbranched carbon skeleton with one carbonyl (C=O) functional group , and one hydroxyl (OH) group on each of the remaining carbon atoms . Therefore, the molecular structure of a simple monosaccharide can be written as H(CHOH) n (C=O)(CHOH) m H, where n + 1 + m = x ; so that its elemental formula is C x H 2 x O x . By convention, the carbon atoms are numbered from 1 to x along
1836-427: A monosaccharide with n asymmetrical carbons has 2 stereoisomers. The number of open chain stereoisomers for an aldose monosaccharide is larger by one than that of a ketose monosaccharide of the same length. Every ketose will have 2 stereoisomers where n > 2 is the number of carbons. Every aldose will have 2 stereoisomers where n > 2 is the number of carbons. These are also referred to as epimers which have
1944-624: 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
2052-402: A pivotal role in metabolism , where the chemical energy is extracted through glycolysis and the citric acid cycle to provide energy to living organisms. Maltose is the dehydration condensate of two glucose molecules. With few exceptions (e.g., deoxyribose ), monosaccharides have the chemical formula (CH 2 O) x , where conventionally x ≥ 3. Monosaccharides can be classified by
2160-830: A saturated fatty acid of the same length. Unsaturated fats may be further classified as monounsaturated (one double-bond) or polyunsaturated (many double-bonds). Furthermore, depending on the location of the double-bond in the fatty acid chain, unsaturated fatty acids are classified as omega-3 or omega-6 fatty acids. Trans fats are a type of unsaturated fat with trans -isomer bonds; these are rare in nature and in foods from natural sources; they are typically created in an industrial process called (partial) hydrogenation . There are nine kilocalories in each gram of fat. Fatty acids such as conjugated linoleic acid , catalpic acid , eleostearic acid and punicic acid , in addition to providing energy, represent potent immune modulatory molecules. Saturated fats (typically from animal sources) have been
2268-522: 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. Ethanol (C 2 H 5 OH) 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.)
SECTION 20
#17328008043612376-534: A specific monosaccharide name . For example, there are 16 distinct aldohexose stereoisomers, but the name "glucose" means a specific pair of mirror-image aldohexoses. In the Fischer projection, one of the two glucose isomers has the hydroxyl at left on C3, and at right on C4 and C5; while the other isomer has the reversed pattern. These specific monosaccharide names have conventional three-letter abbreviations, like "Glu" for glucose and "Thr" for threose . Generally,
2484-726: 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
2592-462: A staple in many world cultures for millennia. Unsaturated fats (e. g., vegetable oil) are considered healthier, while trans fats are to be avoided. Saturated and some trans fats are typically solid at room temperature (such as butter or lard ), while unsaturated fats are typically liquids (such as olive oil or flaxseed oil ). Trans fats are very rare in nature, and have been shown to be highly detrimental to human health, but have properties useful in
2700-445: Is a component of Vitamin B 12 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 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
2808-559: 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
2916-795: 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. An essential amino acid
3024-597: 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
3132-469: 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 . Essential fatty acids (EFAs) are fatty acids that humans and other animals must ingest because
3240-500: 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 ( 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
3348-717: Is contained in prepared foods." More recent comparisons of well-known recommendations on fluid intake have revealed large discrepancies in the volumes of water we need to consume for good health. Therefore, to help standardize guidelines, recommendations for water consumption are included in two recent European Food Safety Authority (EFSA) documents (2010): (i) Food-based dietary guidelines and (ii) Dietary reference values for water or adequate daily intakes (ADI). These specifications were provided by calculating adequate intakes from measured intakes in populations of individuals with "desirable osmolarity values of urine and desirable water volumes per energy unit consumed". For healthful hydration,
Human nutrition - Misplaced Pages Continue
3456-450: Is controlled by the enzyme delta-5-desaturase , which in turn is controlled by hormones such as insulin (up-regulation) and glucagon (down-regulation). Dietary fiber is a carbohydrate , specifically a polysaccharide , which is incompletely absorbed in humans and in some animals. Fiber slows down the absorption of sugar in the gut. The microbiome converts fiber into signals that stimulate gut hormones, which in turn control how quickly
3564-1045: 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
3672-481: Is important as an energy source for colon cells, and may improve metabolic syndrome . In 2016, the U.S. FDA approved a qualified health claim stating that resistant starch might reduce the risk of type 2 diabetes , but with qualifying language for product labels that only limited scientific evidence exists to support this claim. The FDA requires specific labeling language, such as the guideline concerning resistant starch: "High-amylose maize resistant starch may reduce
3780-663: Is inaccurate. Some simple carbohydrates (e.g., fructose) follow different metabolic pathways (e.g., fructolysis ) that result in only a partial catabolism to glucose, while, in essence, many complex carbohydrates may be digested at the same rate as simple carbohydrates. The World Health Organization recommends that added sugars should represent no more than 10% of total energy intake. The most common plant carbohydrate nutrient – starch – varies in its absorption. Starches have been classified as rapidly digestible starch, slowly digestible starch and resistant starch . Starches in plants are resistant to digestion (resistant starch), but cooking
3888-473: Is itself a disaccharide sucrose comprising one molecule of each of the two monosaccharides D -glucose and D -fructose. Each carbon atom that supports a hydroxyl group is chiral , except those at the end of the chain. This gives rise to a number of isomeric forms, all with the same chemical formula. For instance, galactose and glucose are both aldohexoses , but have different physical structures and chemical properties. The monosaccharide glucose plays
3996-597: Is necessary for children to grow physically and mentally, and for normal human biological development. The Recommended Dietary Allowances (RDAs) are scientifically determined levels of essential nutrient intake, deemed sufficient by the Food and Nutrition Board to meet the nutritional needs of nearly all healthy individuals. The first RDAs were published in 1943, during World War II, with the aim of setting standards for optimal nutrition. The initial editions outlined daily nutrient recommendations for various age groups, reflecting
4104-643: 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 nutrients consist of more than
4212-420: Is one of the possible causes of hyponatremia , i.e., low serum sodium. Dietary minerals are inorganic chemical elements required by living organisms, other than the four elements carbon , hydrogen , nitrogen , and oxygen that are present in nearly all organic molecules . Some have roles as cofactors , while others are electrolytes . The term "mineral" is archaic, since the intent is to describe simply
4320-524: Is sufficient. ULs are set a safe fraction below amounts shown to cause health problems. ULs are part of Dietary Reference Intakes . The European Food Safety Authority also reviews the same safety questions and set its own ULs. When too much of one or more nutrients is present in the diet to the exclusion of the proper amount of other nutrients, the diet is said to be unbalanced. High calorie food ingredients such as vegetable oils, sugar and alcohol are referred to as "empty calories" because they displace from
4428-482: Is the minimum to maintain proper hydration . However, the notion that a person should consume eight glasses of water per day cannot be traced to a credible scientific source. The original water intake recommendation in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity
Human nutrition - Misplaced Pages Continue
4536-405: The D - and L - prefixes specifies the configuration at the carbon atom that is second from bottom: D - if the hydroxyl is on the right side, and L - if it is on the left side. Note that the D - and L - prefixes do not indicate the direction of rotation of polarized light, which is a combined effect of the arrangement at all chiral centers. However, the two enantiomers will always rotate
4644-579: The food processing industry, such as rancidity resistance. Most fatty acids are non-essential, meaning the body can produce them as needed, generally from other fatty acids and always by expending energy to do so. However, in humans, at least two fatty acids are essential and must be included in the diet. An appropriate balance of essential fatty acids— omega-3 and omega-6 fatty acids —seems also important for health, although definitive experimental demonstration has been elusive. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for
4752-501: 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
4860-539: The Food and Agriculture Organisation of the United Nations. The EFSA panel also determined intakes for different populations. Recommended intake volumes in the elderly are the same as for adults as despite lower energy consumption, the water requirement of this group is increased due to a reduction in renal concentrating capacity. Pregnant and breastfeeding women require additional fluids to stay hydrated. The EFSA panel proposes that pregnant women should consume
4968-599: The Institute of Medicine has established Tolerable Upper Intake Levels (ULs) for seven vitamins. The term malnutrition addresses 3 broad groups of conditions: In developed countries, the diseases of malnutrition are most often associated with nutritional imbalances or excessive consumption; there are more people in the world who are malnourished due to excessive consumption. According to the United Nations World Health Organization ,
5076-936: The National Academy of Medicine (NAM), part of the National Academies in the United States. Established in 1997, the DRI was created to expand upon the previous standards known as the Recommended Dietary Allowances (RDAs). Unlike the RDAs, the DRI encompasses a broader range of nutritional recommendations. The DRI values are distinct from those found on food and dietary supplement labels in the U.S. and Canada, which use Reference Daily Intakes (RDIs) and Daily Values (%). These labeling standards were originally based on RDAs from 1968 but were updated in 2016. Dietary Reference Values (DRVs) represent
5184-970: 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,
5292-598: The U.S. Department of Agriculture, based on NHANES 2013–2014 surveys, women ages 20 and up consume on average 6.8 grams/day and men consume on average 15.5 grams/day. Ignoring the non-alcohol contribution of those beverages, the average ethanol calorie contributions are 48 and 108 cal/day. Alcoholic beverages are considered empty calorie foods because other than calories, these contribute no essential nutrients. Phytochemicals such as polyphenols are compounds produced naturally in plants (phyto means "plant" in Greek). In general,
5400-546: 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
5508-459: 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
SECTION 50
#17328008043615616-836: 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 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 nutrients are substances within foods that can have
5724-679: 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. Macronutrients are defined in several ways. Macronutrients provide energy: Micronutrients are essential dietary elements required in varying quantities throughout life to serve metabolic and physiological functions . An essential nutrient
5832-452: The backbone, starting from the end that is closest to the C=O group. Monosaccharides are the simplest units of carbohydrates and the simplest form of sugar. If the carbonyl is at position 1 (that is, n or m is zero), the molecule begins with a formyl group H(C=O)− and is technically an aldehyde . In that case, the compound is termed an aldose . Otherwise, the molecule has a ketone group,
5940-1006: 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 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 (B 1 ), riboflavin (B 2 ), niacin (B 3 ), pantothenic acid (B 5 ), pyridoxine (B 6 ), biotin (B 7 ), folate (B 9 ), and cobalamin (B 12 ). The requirement for vitamin D
6048-467: The body. The intestines contain a large population of gut flora . In humans, the four dominant phyla are Bacillota , Bacteroidota , Actinomycetota , and Pseudomonadota . They are essential to digestion and are also affected by food that is consumed. Bacteria are essential for metabolizing food substrates and thereby increasing energy output, and produce a great variety of metabolites, including vitamins and short-chain fatty acids that contribute to
6156-419: The body. Excess amino acids from protein can be converted into glucose and used for fuel through a process called gluconeogenesis . There is an ongoing debate about the differences in nutritional quality and adequacy of protein from vegan , vegetarian and animal sources, though many studies and institutions have found that a well-planned vegan or vegetarian diet contains enough high-quality protein to support
6264-419: The characterization of a biomolecule containing the element with an identifiable and testable function. These include: Except for vitamin D , vitamins are essential nutrients, necessary in the diet for good health. Vitamin D can be synthesized in the skin in the presence of UVB radiation . (Many animal species can synthesize vitamin C , but humans cannot.) Certain vitamin-like compounds that are recommended in
6372-406: The chiral carbon that is furthest removed from the C=O group. Its four bonds must connect to −H, −OH, −CH 2 (OH), and the rest of the molecule. If the molecule can be rotated in space so that the directions of those four groups match those of the analog groups in D -glyceraldehyde's C2, then the isomer receives the D - prefix. Otherwise, it receives the L - prefix. In the Fischer projection,
6480-539: The current EFSA guidelines recommend total water intakes of 2.0 L/day for adult females and 2.5 L/day for adult males. These reference values include water from drinking water, other beverages, and from food. About 80% of our daily water requirement comes from the beverages we drink, with the remaining 20% coming from food. Water content varies depending on the type of food consumed, with fruit and vegetables containing more than cereals, for example. These values are estimated using country-specific food balance sheets published by
6588-461: The cyclic forms predominate, in the solid state and in solutions, and therefore the same name commonly is used for the open- and closed-chain isomers. Thus, for example, the term "glucose" may signify glucofuranose, glucopyranose, the open-chain form, or a mixture of the three. Cyclization creates a new stereogenic center at the carbonyl-bearing carbon. The −OH group that replaces the carbonyl's oxygen may end up in two distinct positions relative to
SECTION 60
#17328008043616696-553: The diet foods that also contain protein, vitamins, minerals and fiber. Pure ethanol provides 7 calories per gram. For distilled spirits , a standard serving in the United States is 1.5 fluid ounces, which at 40% ethanol (80 proof), would be 14 grams and 98 calories. Wine and beer contain a similar range of ethanol for servings of 5 ounces and 12 ounces, 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. According to
6804-612: The diet, such as carnitine , are thought useful for survival and health, but these are not "essential" dietary nutrients because the human body has some capacity to produce them from other compounds. Moreover, thousands of different phytochemicals have recently been discovered in food (particularly in fresh vegetables), which may have desirable properties including antioxidant activity (see below); experimental demonstration has been suggestive but inconclusive. Other essential nutrients not classed as vitamins include essential amino acids (see above ), essential fatty acids (see above ), and
6912-401: The different arrangement of −OH and −H groups at the asymmetric or chiral carbon atoms (this does not apply to those carbons having the carbonyl functional group). Like many chiral molecules, the two stereoisomers of glyceraldehyde will gradually rotate the polarization direction of linearly polarized light as it passes through it, even in solution. The two stereoisomers are identified with
7020-416: The distinctive smell of burning protein, such as the keratin in hair). The body requires amino acids to produce new proteins (protein retention) and to replace damaged proteins (maintenance). Amino acids are soluble in the digestive juices within the small intestine, where they are absorbed into the blood. Once absorbed, they cannot be stored in the body, so they are either metabolized as required or excreted in
7128-524: The double bonds of these two molecules). For example, the aldohexose glucose may form a hemiacetal linkage between the aldehyde group on carbon 1 and the hydroxyl on carbon 4, yielding a molecule with a 5-membered ring, called glucofuranose . The same reaction can take place between carbons 1 and 5 to form a molecule with a 6-membered ring, called glucopyranose . Cyclic forms with a seven-atom ring (the same of oxepane ), rarely encountered, are called heptoses . For many monosaccharides (including glucose),
7236-413: The environment". The U.S. Food and Nutrition Board sets Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins and minerals. EARs and RDAs are part of Dietary Reference Intakes . The DRI documents describe nutrient deficiency signs and symptoms. The U.S. Food and Nutrition Board sets Tolerable Upper Intake Levels (known as ULs) for vitamins and minerals when evidence
7344-431: The essential amino acids; an incomplete protein source lacks one or more of the essential amino acids. It is possible with protein combinations of two incomplete protein sources (e.g., rice and beans) to make a complete protein source, and characteristic combinations are the basis of distinct cultural cooking traditions. However, complementary sources of protein do not need to be eaten at the same meal to be used together by
7452-453: The essential fatty acids along with too much of omega-6 fatty acids relative to omega-3 fatty acids. The conversion rate of omega-6 DGLA to AA largely determines the production of the prostaglandins PGE1 and PGE2. Omega-3 EPA prevents AA from being released from membranes, thereby skewing prostaglandin balance away from pro-inflammatory PGE2 (made from AA) toward anti-inflammatory PGE1 (made from DGLA). The conversion (desaturation) of DGLA to AA
7560-434: The expenditure of energy) to glucose and can be used for energy production just as ordinary glucose, in a process known as gluconeogenesis . By breaking down existing protein, some glucose can be produced internally; the remaining amino acids are discarded, primarily as urea in urine. This occurs naturally when atrophy takes place, or during periods of starvation. The list of nutrients that people are known to require is, in
7668-400: The greatest challenge in developing nations today is not starvation, but insufficient nutrition – the lack of nutrients necessary for the growth and maintenance of vital functions. The causes of malnutrition are directly linked to inadequate macronutrient consumption and disease, and are indirectly linked to factors like "household food security, maternal and child care, health services, and
7776-408: The handedness of each chiral carbon is well specified. Each stereoisomer of a simple open-chain monosaccharide can be identified by the positions (right or left) in the Fischer diagram of the chiral hydroxyls (the hydroxyls attached to the chiral carbons). Most stereoisomers are themselves chiral (distinct from their mirror images). In the Fischer projection, two mirror-image isomers differ by having
7884-549: The human body, and about ten of these are essential. The synthesis of some amino acids can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress, and those are called conditionally essential. A diet that contains adequate amounts of amino acids (especially those that are essential) is particularly important in some situations: during early development and maturation, pregnancy, lactation, or injury (a burn, for instance). A complete protein source contains all
7992-560: The intestinal contents, and insoluble fiber facilitates peristalsis – the rhythmic muscular contractions of the intestines which move contents along the digestive tract. Some soluble and insoluble fibers produce a solution of high viscosity ; this is essentially a gel, which slows the movement of food through the intestines. Fermentable fibers are used as food by the microbiome , mildly increasing bulk, and producing short-chain fatty acids and other metabolites, including vitamins, hormones, and glucose. One of these metabolites, butyrate ,
8100-412: The ionic forms found in such sources. On the other hand, minerals are often artificially added to the diet as supplements; the most well-known is likely iodine in iodized salt which prevents goiter . Elements with recommended dietary allowance ( RDA ) greater than 150 mg/day are, in alphabetical order: Many elements are required in smaller amounts (microgram quantities), usually because they play
8208-591: The latest scientific insights at the time (NRC, 1943). The history and evolution of the RDAs have been extensively detailed by the chair of the first Committee on Recommended Dietary Allowances (Roberts, 1958). Over the years, the RDAs have been periodically updated, with the current version being the tenth edition. Originally intended to address nutrition issues related to national defense, the RDAs now serve multiple roles, including guiding food supply planning for population groups, interpreting dietary intake data, establishing standards for food assistance programs, assessing
8316-424: The less common elements in the diet. Some are heavier than the four just mentioned – including several metals , which often occur as ions in the body. Some dietitians recommend that these be supplied from foods in which they occur naturally, or at least as complex compounds, or sometimes even from natural inorganic sources (such as calcium carbonate from ground oyster shells). Some are absorbed much more readily in
8424-402: The light in opposite directions, by the same amount. See also D/L system . A monosaccharide often switches from the acyclic (open-chain) form to a cyclic form, through a nucleophilic addition reaction between the carbonyl group and one of the hydroxyl groups of the same molecule. The reaction creates a ring of carbon atoms closed by one bridging oxygen atom. The resulting molecule has
8532-576: The macronutrients depends on such factors as absorption and digestive effort, which vary substantially from instance to instance. Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons. A third class of dietary material, fiber (i.e., nondigestible material such as cellulose), seems also to be required, for both mechanical and biochemical reasons, though the exact reasons remain unclear. For all age groups, males on average need to consume higher amounts of macronutrients than females. In general, intakes increase with age until
8640-811: The metabolism in a wide variety of ways. These metabolites are responsible for stimulating cell growth, repressing the growth of harmful bacteria, priming the immune system to respond only to pathogens, helping to maintain a healthy gut barrier, control gene expression by epigenetic regulation and defending against some infectious diseases. Essential nutrient 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
8748-716: 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 ). Monosaccharides Monosaccharides (from Greek monos : single, sacchar : sugar), also called simple sugars , are
8856-433: The minerals discussed in the preceding section. Vitamin deficiencies may result in disease conditions: goiter , scurvy , osteoporosis , impaired immune system , disorders of cell metabolism , certain forms of cancer, symptoms of premature aging , and poor psychological health (including eating disorders ), among many others. Excess levels of some vitamins are also dangerous to health. The Food and Nutrition Board of
8964-549: The molecular graph is symmetrical, as in the 3-ketopentoses H(CHOH) 2 (CO)(CHOH) 2 H, and the two halves are mirror images of each other. In that case, mirroring is equivalent to a half-turn rotation. For this reason, there are only three distinct 3-ketopentose stereoisomers, even though the molecule has two chiral carbons. Distinct stereoisomers that are not mirror-images of each other usually have different chemical properties, even in non-chiral environments. Therefore, each mirror pair and each non-chiral stereoisomer may be given
9072-420: The molecule contains a stereogenic center , specifically a carbon atom that is chiral (connected to four distinct molecular sub-structures). Those four bonds can have any of two configurations in space distinguished by their handedness . In a simple open-chain monosaccharide, every carbon is chiral except the first and the last atoms of the chain, and (in ketoses) the carbon with the keto group. For example,
9180-657: The number x of carbon atoms they contain: triose (3), tetrose (4), pentose (5), hexose (6), heptose (7), and so on. Glucose, used as an energy source and for the synthesis of starch, glycogen and cellulose, is a hexose . Ribose and deoxyribose (in RNA and DNA , respectively) are pentose sugars. Examples of heptoses include the ketoses mannoheptulose and sedoheptulose . Monosaccharides with eight or more carbons are rarely observed as they are quite unstable. In aqueous solutions monosaccharides exist as rings if they have more than four carbons. Simple monosaccharides have
9288-440: The nutritional adequacy of food supplies, designing nutrition education initiatives, aiding in the development of new food products, and setting guidelines for food labeling. However, the data underpinning these nutrient requirement estimates are often limited. The nutritional requirements system adopted by the United States and Canada refers to Dietary Reference Intake (DRI). The DRI is a set of nutritional guidelines developed by
9396-619: The nutritional standards set by the United Kingdom's Department of Health and the European Food Safety Authority ( EFSA ) for assessing and planning dietary intakes. The UK's Department of Health introduced these guidelines in 1991 with the publication of Dietary Reference Values for Food Energy and Nutrients for the United Kingdom . This document provides recommended nutrient intakes for the UK population, offering
9504-697: The population, ensuring a more personalized approach to nutrition. The seven major classes of nutrients are carbohydrates, fats , fiber , minerals , proteins , vitamins , and water. Nutrients can be grouped as either macronutrients or micronutrients (needed in small quantities). Carbohydrates, fats, and proteins are macronutrients, and provide energy. Water and fiber are macronutrients, but do not provide energy. The micronutrients are minerals and vitamins. The macronutrients (excluding fiber and water) provide structural material (amino acids from which proteins are built, and lipids from which cell membranes and some signaling molecules are built), and energy . Some of
9612-433: The positions of all chiral hydroxyls reversed right-to-left. Mirror-image isomers are chemically identical in non-chiral environments, but usually have very different biochemical properties and occurrences in nature. While most stereoisomers can be arranged in pairs of mirror-image forms, there are some non-chiral stereoisomers that are identical to their mirror images, in spite of having chiral centers. This happens whenever
9720-410: The prefixes D - and L -, according to the sense of rotation: D -glyceraldehyde is dextrorotatory (rotates the polarization axis clockwise), while L -glyceraldehyde is levorotatory (rotates it counterclockwise). The D - and L - prefixes are also used with other monosaccharides, to distinguish two particular stereoisomers that are mirror-images of each other. For this purpose, one considers
9828-701: 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 )
9936-440: The protein requirements of both sedentary and active people at all stages of life. Water is excreted from the body in multiple forms; including urine and feces , sweating , and by water vapour in the exhaled breath. Therefore, it is necessary to adequately rehydrate to replace lost fluids. Early recommendations for the quantity of water required for maintenance of good health suggested that six to eight glasses of water daily
10044-405: 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. See Vitamin , Mineral (nutrient) , Protein (nutrient) An inadequate amount of a nutrient
10152-487: The resistant starch content of a traditional African diet was 38 grams/day. The resistant starch consumption from countries with high starch intakes has been estimated to be 30-40 grams/day. In contrast, the average consumption of resistant starch in the United States was estimated to be 4.9 grams/day (range 2.8-7.9 grams of resistant starch/day). A molecule of dietary fat typically consists of several fatty acids (containing long chains of carbon and hydrogen atoms), bonded to
10260-431: The ring's midplane. Thus each open-chain monosaccharide yields two cyclic isomers ( anomers ), denoted by the prefixes α- and β-. The molecule can change between these two forms by a process called mutarotation , that consists in a reversal of the ring-forming reaction followed by another ring formation. The stereochemical structure of a cyclic monosaccharide can be represented in a Haworth projection . In this diagram,
10368-402: The risk of type 2 diabetes. FDA has concluded that there is limited scientific evidence for this claim." Proteins are the basis of many animal body structures (e.g. muscles, skin, and hair) and form the enzymes that control chemical reactions throughout the body. Each protein molecule is composed of amino acids which contain nitrogen and sometimes sulphur (these components are responsible for
10476-434: The same volume of water as non-pregnant women, plus an increase in proportion to the higher energy requirement, equal to 300 mL/day. To compensate for additional fluid output, breastfeeding women require an additional 700 mL/day above the recommended intake values for non-lactating women. Dehydration and over-hydration – too little and too much water, respectively – can have harmful consequences. Drinking too much water
10584-665: The second or third decade of life. Some nutrients can be stored – the fat-soluble vitamins – while others are required more or less continuously. Poor health can be caused by a lack of required nutrients, or for some vitamins and minerals, too much of a required nutrient. Essential nutrients cannot be synthesized by the body, and must be obtained from food. Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple monosaccharides (glucose, fructose, galactose) to complex polysaccharides (starch, glycogen). Fats are triglycerides , made of assorted fatty acid monomers bound to
10692-468: The simplest forms of sugar and the most basic units ( monomers ) from which all carbohydrates are built. Chemically, monosaccharides are polyhydroxy aldehydes with the formula H-[CHOH] n -CHO or polyhydroxy ketones with the formula H-[CHOH] m -CO-[CHOH] n -H with three or more carbon atoms. They are usually colorless , water - soluble , and crystalline organic solids. Contrary to their name (sugars), only some monosaccharides have
10800-440: The starch in the presence of water can break down the starch granule and releases the glucose chains, making them more easily digestible by human digestive enzymes. Historically, food was less processed and starches were contained within the food matrix, making them less digestible. Modern food processing has shifted carbohydrate consumption from less digestible and resistant starch to much more rapidly digestible starch. For instance,
10908-658: The stomach empties, regulate blood sugar levels, and influence feelings of hunger. Like all carbohydrates, when fiber is digested, it can produce four calories (kilocalories) of energy per gram, but in most circumstances, it accounts for less than that because of its limited absorption and digestibility. The two subcategories are insoluble and soluble fiber. Whole grains, beans, and other legumes , fruits (especially plums , prunes , and figs ), and vegetables are good sources of dietary fiber. Fiber has three primary mechanisms, which in general determine their health impact: bulking, viscosity and fermentation. Fiber provides bulk to
11016-423: The structural material can also be used to generate energy internally, and in either case it is measured in joules or kilocalories (often called "Calories" and written with a capital 'C' to distinguish them from little 'c' calories). Carbohydrates and proteins provide 17 kJ approximately (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) per gram. However, the net energy derived from
11124-518: The suffixes "-ose" for aldoses and "-ulose" for ketoses. In the latter case, if the carbonyl is not at position 2, its position is then indicated by a numeric infix. So, for example, H(C=O)(CHOH) 4 H is pentose, H(CHOH)(C=O)(CHOH) 3 H is pentulose, and H(CHOH) 2 (C=O)(CHOH) 2 H is pent-3-ulose. Two monosaccharides with equivalent molecular graphs (same chain length and same carbonyl position) may still be distinct stereoisomers , whose molecules differ in spatial orientation. This happens only if
11232-448: The term identifies compounds that are prevalent in plant foods, but are not proven to be essential for human nutrition, as of 2018. There is no conclusive evidence in humans that polyphenols or other non-nutrient compounds from plants confer health benefits, mainly because these compounds have poor bioavailability , i.e., following ingestion, they are digested into smaller metabolites with unknown functions, then are rapidly eliminated from
11340-413: The triketose H(CHOH)(C=O)(CHOH)H (glycerone, dihydroxyacetone ) has no stereogenic center, and therefore exists as a single stereoisomer. The other triose, the aldose H(C=O)(CHOH) 2 H ( glyceraldehyde ), has one chiral carbon—the central one, number 2—which is bonded to groups −H, −OH, −C(OH)H 2 , and −(C=O)H. Therefore, it exists as two stereoisomers whose molecules are mirror images of each other (like
11448-454: The urine. Proteins consist of amino acids in different proportions. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition. For all animals, some amino acids are essential (an animal cannot produce them internally so they must be eaten) and some are non-essential (the animal can produce them from other nitrogen-containing compounds). About twenty amino acids are found in
11556-474: The words of Marion Nestle , "almost certainly incomplete". Carbohydrates may be classified as monosaccharides , disaccharides or polysaccharides depending on the number of monomer (sugar) units they contain. They are a diverse group of substances, with a range of chemical, physical and physiological properties. They make up a large part of foods such as rice , noodles , bread , and other grain -based products, but they are not an essential nutrient, meaning
11664-399: The α-isomer for the pyranose form of a D -aldohexose has the −OH of the anomeric carbon below the plane of the carbon atoms, while the β-isomer has the −OH of the anomeric carbon above the plane. Pyranoses typically adopt a chair conformation, similar to that of cyclohexane . In this conformation, the α-isomer has the −OH of the anomeric carbon in an axial position, whereas the β-isomer has
#360639