B vitamins: Difference between revisions

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'''B vitamins''' are a class of water-soluble [[vitamin]]s that play important roles in [[Cell (biology)|cell]] [[metabolism]] and synthesis of [[red blood cell]]s. They are a [[chemical]]ly diverse class of compounds, but are associated in [[Diet (nutrition)|diet]], often occurring together in the same foods. [[Dietary supplement]]s containing all eight are referred to as a '''vitamin B complex'''. Individual B vitamins are referred to by B-number or by chemical name, such as B₁ for thiamine, B₂ for riboflavin, and B₃ for niacin, while some are more commonly recognized by name than by number, such as pantothenic acid (B₅), biotin (B₇), and folate (B₉).

Each B vitamin is either a [[cofactor (biochemistry)|cofactor]] (generally a [[cofactor (biochemistry)|coenzyme]]) for key [[metabolism|metabolic]] processes or is a [[precursor (chemistry)|precursor]] needed to make one.

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|+ List of B vitamins

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'''Note:''' Other substances once thought to be vitamins were given B-numbers, but were disqualified once discovered to be either manufactured by the body or not essential for life. See [[#Related compounds]] for numbers 4, [[Inositol|8]], [[4-Aminobenzoic acid|10]], 11, and others.

B vitamins are found in abundance in meat, eggs, and [[dairy product]]s. Processed carbohydrates such as sugar and white flour tend to have lower B vitamin than their unprocessed counterparts. For this reason, it is common in many countries (including the United States) that the B vitamins thiamine, riboflavin, niacin, and folic acid are added back to white flour after processing. This is referred to as "[[enriched flour]]" on food labels. B vitamins are particularly concentrated in meat such as turkey, tuna and liver.

Sources for B vitamins also include [[spinach]], [[legume]]s ([[Pulse (legume)|pulses]] or beans), whole grains, [[asparagus]], potatoes, bananas, chili peppers, [[breakfast cereal]]s.

The B₁₂ vitamin is not abundantly available from [[Vitamin B12#Non-animal sources|plant products]] (although it has been found in moderate abundance in fermented vegetable products, certain seaweeds, and in certain mushrooms, with the [[bioavailability]] of the vitamin in these cases remaining uncertain), making B₁₂ deficiency a legitimate concern for those maintaining a [[vegan]] diet. Manufacturers of plant-based foods will sometimes report B₁₂ content, leading to confusion about what sources yield B₁₂. The confusion arises because the standard [[US Pharmacopeia]] (USP) method for measuring the B₁₂ content does not measure the B₁₂ directly. Instead, it measures a bacterial response to the food. Chemical variants of the B₁₂ vitamin found in plant sources are active for bacteria, but cannot be used by the human body. This same phenomenon can cause significant over-reporting of B₁₂ content in other types of foods as well.

A common way to increase vitamin B intake is by using [[dietary supplement]]s. B vitamins are commonly added to [[energy drink]]s, many of which have been marketed with large amounts of B vitamins.

Because they are soluble in water, excess B vitamins are generally readily excreted, although individual absorption, use and metabolism may vary. The elderly and athletes may need to supplement their intake of B₁₂ and other B vitamins due to problems in absorption and increased needs for energy production. In cases of severe deficiency, B vitamins, especially B₁₂, may also be delivered by injection to reverse deficiencies. Both type 1 and type 2 diabetics may also be advised to supplement thiamine based on high prevalence of low plasma thiamine concentration and increased thiamine clearance associated with diabetes. Also, folate deficiency in early embryo development has been linked to [[neural tube defects]]. Thus, women planning to become pregnant are usually encouraged to increase daily dietary folate intake or take a supplement.

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{{See also|Vitamin deficiency#Water-soluble vitamins}}

Several named vitamin deficiency diseases may result from the lack of sufficient B vitamins. Deficiencies of other B vitamins result in symptoms that are not part of a named deficiency disease.

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!Vitamin!! Name !! Deficiency effects

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{{Anchor|B vitamin toxicity}}<!-- Former section title -->

Because water-soluble B vitamins are eliminated in the urine, taking large doses of certain B vitamins usually only produces transient side effects (only exception is pyridoxine). General side effects may include restlessness, nausea and insomnia. These side effects are almost always caused by dietary supplements and not foodstuffs.

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! Vitamin !! Tolerable Upper Intake Level (UL) !! Harmful effects

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! Vitamin!! Name !! Discoverer!!Date!!Notes

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Many of the following substances have been referred to as vitamins as they were once believed to be vitamins. They are no longer considered as such, and the numbers that were assigned to them now form the "gaps" in the true series of B-complex vitamins described above (for example, there is no vitamin B₄). Some of them, though not essential to humans, are essential in the diets of other organisms; others have no known nutritional value and may even be toxic under certain conditions.

* '''Vitamin B₄''': can refer to the distinct chemicals [[choline]], [[adenine]], or [[carnitine]].

{{Vitamins}}

{{Nutritional pathology}}

{{二次利用|date=14 December 2023}}

{{DEFAULTSORT:B Vitamins}}

[[Category:B vitamins| ]]

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