Vitamin/ja: Difference between revisions

| [[proprioception/ja|プロプリオセプション]]障害、神経損傷（100 mg/日を超える用量)

Five people have been awarded [[Nobel Prize]]s for direct and indirect studies of vitamin B₁₂: [[George Whipple]], [[George Minot]] and [[William P. Murphy]] (1934), [[Alexander R. Todd]] (1957), and [[Dorothy Hodgkin]] (1964).

In 1967, [[George Wald]], [[Ragnar Granit]] and [[Haldan Keffer Hartline]] were awarded the Nobel Prize in Physiology and Medicine  "...for their discoveries concerning the primary physiological and chemical visual processes in the eye." Wald's contribution was discovering the role vitamin A had in the process.

===History of promotional marketing===

Once discovered, vitamins were actively promoted in articles and advertisements in ''[[McCall's]]'', ''[[Good Housekeeping]]'', and other media outlets. Marketers enthusiastically promoted [[cod-liver oil]], a source of vitamin D, as "bottled sunshine", and bananas as a "natural vitality food". They promoted foods such as [[yeast]] cakes, a source of B vitamins, on the basis of scientifically determined nutritional value, rather than taste or appearance. In 1942, when flour [[food fortification|enrichment]] with nicotinic acid began, a headline in the popular press said "Tobacco in Your Bread." In response, the Council on Foods and Nutrition of the [[American Medical Association]] approved of the [[Food and Nutrition Board]]'s new names ''niacin'' and ''niacin amide'' for use primarily by non-scientists. It was thought appropriate to choose a name to dissociate nicotinic acid from [[nicotine]], to avoid the perception that vitamins or niacin-rich food contains nicotine, or that cigarettes contain vitamins. The resulting name ''niacin'' was derived from ''{{strong|ni}}cotinic {{strong|ac}}id'' + ''vitam{{strong|in}}''. Researchers also focused on the need to ensure adequate nutrition, especially to compensate for what was lost in the manufacture of [[processed foods]].

Robert W. Yoder is credited with first using the term ''vitamania'', in 1942, to describe the appeal of relying on nutritional supplements rather than on obtaining vitamins from a varied diet of foods. The continuing preoccupation with a healthy lifestyle led to an obsessive consumption of vitamins and multi-vitamins, the beneficial effects of which are questionable. As one example, in the 1950s, the [[Wonder Bread]] company sponsored the [[Howdy Doody]] television show, with host [[Buffalo Bob Smith]] telling the audience, "Wonder Bread builds strong bodies 8 ways", referring to the number of [[Food additive|added nutrients]].

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==Etymology==

The term "vitamin" was derived from "vitamine", a [[compound (linguistics)|compound word]] coined in 1912 by the [[biochemist]] Casimir Funk while working at the [[Lister Institute of Preventive Medicine]]. Funk created the name from ''vital'' and ''amine'', because it appeared that these organic micronutrient food factors that prevent beriberi and perhaps other similar dietary-deficiency diseases were required for life, hence "vital", and were chemical amines, hence "amine". This was true of [[thiamine]], but after it was found that vitamin C and other such micronutrients were not amines, the word was shortened to "vitamin" in English.

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==Classification==

Vitamins are classified as either [[Hydrophilicity|water-soluble]] or [[lipophilicity|fat-soluble]]. In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption. Because they are not as readily stored, more consistent intake is important. Fat-soluble vitamins are absorbed through the [[gastrointestinal tract]] with the help of [[lipid]]s (fats). Vitamins A and D can accumulate in the body, which can result in dangerous [[hypervitaminosis]]. Fat-soluble vitamin deficiency due to malabsorption is of particular significance in [[cystic fibrosis]].

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==Anti-vitamins==

{{Main|Antinutrient}}

Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, [[avidin]] is a protein in raw egg whites that inhibits the absorption of [[biotin]]; it is deactivated by cooking. Pyrithiamine, a synthetic compound, has a molecular structure similar to thiamine, [[vitamin B1|vitamin B₁]], and inhibits the [[enzyme]]s that use thiamine.

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==Biochemical functions==

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===On fetal growth and childhood development===

{{main|Nutrition and pregnancy}}

Vitamins are essential for the normal growth and development of a multicellular organism. Using the genetic blueprint inherited from its parents, a [[fetus]] [[prenatal development|develop]]s from the nutrients it absorbs. It requires certain vitamins and minerals to be present at certain times. These nutrients facilitate the chemical reactions that produce among other things, [[skin]], [[bone]], and [[muscle]]. If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage.

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===On adult health maintenance===

Once growth and development are completed, vitamins remain essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism; they also enable a multicellular life form to efficiently use chemical energy provided by food it eats, and to help process the proteins, carbohydrates, and fats required for [[cellular respiration]].

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== Intake ==

===Sources===

For the most part, vitamins are obtained from the diet, but some are acquired by other means: for example, microorganisms in the [[gut flora]] produce vitamin K and biotin; and one form of vitamin D is synthesized in skin cells when they are exposed to a certain wavelength of ultraviolet light present in [[sunlight]]. Humans can produce some vitamins from precursors they consume: for example, vitamin A is synthesized from [[beta carotene]]; and [[Niacin (nutrient)|niacin]] is synthesized from the [[amino acid]] [[tryptophan]]. Vitamin C can be synthesized by some species but not by others. [[Vitamin B12|Vitamin B₁₂]] is the only vitamin or nutrient not available from plant sources. The Food Fortification Initiative lists countries which have mandatory fortification programs for vitamins folic acid, niacin, vitamin A and vitamins B₁, B₂ and B₁₂.

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===Deficient intake===

{{See also|Vitamin deficiency}}

The [[human body|body's]] stores for different vitamins vary widely; vitamins A, D, and B₁₂ are stored in significant amounts, mainly in the [[liver]], and an adult's diet may be deficient in vitamins A and D for many months and B₁₂ in some cases for years, before developing a deficiency condition. However, vitamin B₃ (niacin and niacinamide) is not stored in significant amounts, so stores may last only a couple of weeks. For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores.

Well-researched human vitamin deficiencies involve thiamine (beriberi), niacin ([[pellagra]]), vitamin C (scurvy), folate (neural tube defects) and vitamin D (rickets). In much of the developed world these deficiencies are rare due to an adequate supply of food and the addition of vitamins to common foods. In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.

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===Excess intake===

{{See also|Hypervitaminosis}}

Some vitamins have documented acute or chronic toxicity at larger intakes, which is referred to as hypertoxicity. The European Union and the governments of several countries have established [[Tolerable upper intake levels]] (ULs) for those vitamins which have documented toxicity (see table). The likelihood of consuming too much of any vitamin from food is remote, but excessive intake ([[vitamin poisoning]]) from dietary supplements does occur. In 2016, overdose exposure to all formulations of vitamins and multi-vitamin/mineral formulations was reported by 63,931 individuals to the [[American Association of Poison Control Centers]] with 72% of these exposures in children under the age of five. In the US, analysis of a national diet and supplement survey reported that about 7% of adult supplement users exceeded the UL for folate and 5% of those older than age 50 years exceeded the UL for vitamin A.

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===Effects of cooking===

The [[USDA]] has conducted extensive studies on the percentage losses of various nutrients from food types and cooking methods. The table below shows whether various vitamins are susceptible to loss from heat—such as heat from boiling, steaming, frying, etc. The effect of cutting vegetables can be seen from exposure to air and light. Water-soluble vitamins such as B and C dissolve into the water when a vegetable is boiled, and are then lost when the water is discarded.

! rowspan="2" |Vitamin

! colspan="4" |'''Is substance susceptible to losses under given condition?'''

!Soluble in Water

!Air Exposure

!Light Exposure

!Heat Exposure

|Vitamin A

| relatively stable

|Vitamin C

| very unstable

| Vitamin D

| Vitamin E

|Vitamin K

|Thiamine (B₁)

|Riboflavin (B₂)

|Niacin (B₃)

|Pantothenic Acid (B₅)

|Vitamin B₆

|Biotin (B₇)

|Folic Acid (B₉)

| when dry

| at high temp

|Cobalamin (B₁₂)

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==Recommended levels==

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&nbsp;mg/day in India to 155&nbsp;mg/day for the European Union. The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins, 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.

! rowspan="2" |Nutrient !! rowspan="2" |U.S. EAR!! rowspan="2" |Highest U.S.<br />RDA or AI!! rowspan="2" |Highest EU<br />PRI or AI!! colspan="3" |Upper limit (UL) !! rowspan="2" |Unit

|[[Vitamin A]]|| 625 || 900 || 1300 || 3000 || 3000 || 2700 || µg

|[[Vitamin C]]|| 75 || 90 || 155 || 2000 || ND || ND || mg

|[[Vitamin D]]|| 10 || 15 || 15 || 100 || 100 || 100 || µg

|[[Vitamin K]]|| NE || 120 || 70 || ND || ND || ND || µg

|[[Tocopherol|α-tocopherol]] (Vitamin E) || 12 || 15 || 13 || 1000 || 300 || 650-900 || mg

|[[Thiamin]] (Vitamin B₁) || 1.0 || 1.2 || 0.1&nbsp;mg/MJ || ND || ND || ND || mg

|[[Riboflavin]] (Vitamin B₂) || 1.1 || 1.3 || 2.0 || ND || ND || ND || mg

|[[Niacin (nutrient)|Niacin]] (Vitamin B₃) || 12 || 16 || 1.6&nbsp;mg/MJ || 35 || 10 || 60-85 || mg

|[[Pantothenic acid]] (Vitamin B₅) || NE || 5 || 7 || ND || ND || ND || mg

|[[Vitamin B6|Vitamin B₆]]|| 1.1 || 1.3 || 1.8 || 100 || 25 || 40-60 || mg

|[[Biotin]] (Vitamin B₇) || NE || 30 || 45 || ND || ND || ND || µg

|[[Folate]] (Vitamin B₉) || 320 || 400 || 600 || 1000 || 1000 || 900-1000|| µg

|[[Cyanocobalamin]] (Vitamin B₁₂) || 2.0 || 2.4 || 5.0 || ND || ND || ND || µg

'''EAR''' US Estimated Average Requirements.

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

'''AI''' US and EFSA 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.

'''UL or Upper Limit'''  Tolerable upper intake levels.

'''ND''' ULs have not been determined.

'''NE''' EARs have not been established.

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==Supplementation==

[[File:500 mg calcium supplements with vitamin D.jpg|thumb|upright=1.25|Calcium combined with vitamin D (as calciferol) supplement tablets with fillers.]]

In those who are otherwise healthy, there is little evidence that supplements have any benefits with respect to [[cancer]] or [[cardiovascular disease|heart disease]]. Vitamin A and E supplements not only provide no health benefits for generally healthy individuals, but they may increase mortality, though the two large studies that support this conclusion included [[tobacco smoking|smokers]] for whom it was already known that beta-carotene supplements can be harmful. A 2018 meta-analysis found no evidence that intake of vitamin D or calcium for community-dwelling elderly people reduced bone fractures.

Europe has regulations that define limits of vitamin (and mineral) dosages for their safe use as dietary supplements. Most vitamins that are sold as dietary supplements are not supposed to exceed a maximum daily dosage referred to as the [[tolerable upper intake level]] (UL or Upper Limit). Vitamin products above these regulatory limits are not considered supplements and should be registered as prescription or non-prescription ([[over-the-counter drug]]s) due to their potential side effects. The European Union, United States and Japan establish ULs.

[[Dietary supplement]]s often contain vitamins, but may also include other ingredients, such as minerals, herbs, and botanicals. [[Scientific evidence]] supports the benefits of dietary supplements for persons with certain health conditions. In some cases, vitamin supplements may have unwanted effects, especially if taken before surgery, with other dietary supplements or medicines, or if the person taking them has certain health conditions. They may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.

{{see also|Megavitamin therapy}}

===Governmental regulation===

Most countries place dietary supplements in a special category under the general umbrella of ''foods'', not drugs. As a result, the manufacturer, and not the government, has the responsibility of ensuring that its dietary supplement products are safe before they are marketed. Regulation of supplements varies widely by country. In the [[United States]], a dietary supplement is defined under the [[Dietary Supplement Health and Education Act]] of 1994. There is no FDA approval process for dietary supplements, and no requirement that manufacturers prove the safety or efficacy of supplements introduced before 1994. The [[Food and Drug Administration]] must rely on its Adverse Event Reporting System to monitor adverse events that occur with supplements.

In 2007, the US [[Code of Federal Regulations]] (CFR) Title 21, part III took effect, regulating Good Manufacturing Practices (GMPs) in the manufacturing, packaging, labeling, or holding operations for dietary supplements. Even though product registration is not required, these regulations mandate production and quality control standards (including testing for identity, purity and adulterations) for dietary supplements. In the European Union, the [[Food Supplements Directive]] requires that only those supplements that have been proven safe can be sold without a prescription. For most vitamins, [[pharmacopoeia|pharmacopoeial standards]] have been established. In the United States, the [[United States Pharmacopeia]] (USP) sets standards for the most commonly used vitamins and preparations thereof. Likewise, monographs of the [[European Pharmacopoeia]] (Ph.Eur.) regulate aspects of identity and purity for vitamins on the European market.

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==Naming==

|+Nomenclature of reclassified vitamins

! Previous name

! Chemical name

! Reason for name change

| Vitamin B₄

|[[Adenine]]

| DNA metabolite; synthesized in body

| Vitamin B₈

|[[Adenylic acid]]

| DNA metabolite; synthesized in body

| Vitamin B_T

|[[Carnitine]]

| Synthesized in body

| Vitamin F

|[[Essential fatty acid]]s

| Needed in large quantities (does<br /> not fit the definition of a vitamin).

| Vitamin G

|[[Riboflavin]]

| Reclassified as [[B vitamins|Vitamin B₂]]

| Vitamin H

|[[Biotin]]

| Reclassified as [[B vitamins|Vitamin B₇]]

| Vitamin J

|[[Catechol]], [[Flavin group|Flavin]]

| Catechol nonessential; flavin reclassified<br /> as [[B vitamins|Vitamin B₂]]

| Vitamin L₁

|[[Anthranilic acid]]

| Nonessential

| Vitamin L₂

|[[5′-Methylthioadenosine]]

| RNA metabolite; synthesized in body

| Vitamin M or B_c

|[[Folate]]

| Reclassified as [[B vitamins|Vitamin B₉]]

| Vitamin P

|[[Flavonoids]]

| Many compounds, not proven essential

| Vitamin PP

|[[Niacin (nutrient)|Niacin]]

| Reclassified as [[B vitamins|Vitamin B₃]]

| Vitamin S

|[[Salicylic acid]]

| Nonessential

| Vitamin U

|[[S-Methylmethionine]]

| Protein metabolite; synthesized in body

The Danish-speaking scientists who isolated and described vitamin&nbsp;K (in addition to naming it as such) did so because the vitamin is intimately involved in the coagulation of blood following wounding (from the [[Danish language|Danish]] word ''Koagulation''). At the time, most (but not all) of the letters from F through to J were already designated, so the use of the letter K was considered quite reasonable. The table ''Nomenclature of reclassified vitamins'' lists chemicals that had previously been classified as vitamins, as well as the earlier names of vitamins that later became part of the B-complex.

The missing numbered  B vitamins were reclassified or determined not to be vitamins. For example, B₉ is [[folic acid]] and five of the folates are in the range B₁₁ through B₁₆. Others, such as [[4-Aminobenzoic acid|PABA]] (formerly B₁₀), are biologically inactive, toxic, or with unclassifiable effects in humans, or not generally recognised as vitamins by science, such as the highest-numbered, which some [[naturopath]] practitioners call B₂₁ and B₂₂. There are also lettered B substances (e.g., B_m) listed at [[B vitamins]] that are not recognized as vitamins. There are other "D vitamins" now recognised as other substances, which some sources of the same type number up to D₇. The controversial cancer treatment [[laetrile]] was at one point lettered as vitamin B₁₇. There appears to be no consensus on the existence of substances that may have at one time been named as vitamins Q, R, T, V, W, X, Y or Z.

"Vitamin N" is a term popularized for the mental health benefits of spending time in nature settings. "Vitamin I" is slang among athletes for frequent/daily consumption of [[ibuprofen]] as a pain-relieving treatment.

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== See also ==

{{Portal|Food}}

*[[Vitamin deficiency]]

*[[Hypervitaminosis]]

*[[Human nutrition]]