B vitamins

B vitamin supplement tablets

The B vitamins are eight water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to as vitamin B (much as people refer to vitamin C or vitamin D). Later research showed that they are chemically distinct vitamins that often coexist in the same foods. In general, supplements containing all eight are referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific name of each vitamin (e.g., B₁, B₂, B₃ etc.).

List of B vitamins

• Vitamin B₁ (thiamine)
• Vitamin B₂ (riboflavin)
• Vitamin B₃ (niacin or niacinamide, sometimes also known as vitamin PP)
• Vitamin B₅ (pantothenic acid)
• Vitamin B₆ (pyridoxine, pyridoxal, or pyridoxamine, or pyridoxine hydrochloride)
• Vitamin B₇ (biotin)
• Vitamin B₈ (inositol)
• Vitamin B₉ (folic acid)
• Vitamin B₁₂ (various cobalamins; commonly cyanocobalamin in vitamin supplements)

Health benefits

The B vitamins may be necessary in order to:

• Support and increase the rate of metabolism
• Maintain healthy skin and muscle tone
• Enhance immune and nervous system function
• Promote cell growth and division, including that of the red blood cells that help prevent anemia
• Reduce the risk of pancreatic cancer - one of the most lethal forms of cancer^[1] - when consumed in food, but not when ingested in vitamin tablet form.^[2][3]

All B vitamins are water-soluble, and are dispersed throughout the body. Most of the B vitamins must be replenished regularly, since any excess is excreted in the urine.^[4]

A 2010 study concluded that taking folic acid (B9), Vitamins B6 and B12 may slow brain atrophy in patients with Mild Cognitive Impairment. Such atrophy is one predictor of conversion from MCI to Alzheimer's disease.^[5] However, the study was conducted by a former collaborator of Patrick Holford and the result has been criticised by Carl Heneghan, Director of the Centre for Evidence Based Medicine and clinical lecturer at the University of Oxford, for excluding the one third of initial participants who dropped out or were not followed up,and for quoting a "30% reduction in rate of decline" which translates to only a 0.3% absolute change.^[6]

B vitamin deficiency

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.

B vitamin toxicity

Although most B vitamins are eliminated regularly in the urine, taking large doses of certain B vitamins may produce harmful effects.

B vitamin sources

B vitamins are found in all whole, unprocessed foods. Processed carbohydrates, such as sugar and white flour, tend to have lower B vitamin content than their unprocessed counterparts. B vitamins are particularly concentrated in meat and meat products such as liver, turkey, and tuna.^[12] Other good sources for B vitamins are whole grains, potatoes, bananas, lentils, chile peppers, tempeh, beans, nutritional yeast, brewer's yeast, and molasses. Marmite and Vegemite bill themselves as "one of the world's richest known sources of vitamin B". Although the yeast used to make beer results in beer's being a source of B vitamins,^[13] their bioavailability ranges from poor to negative given the fact consumption of ethanol is known to inhibit absorption of thiamine (B₁),^[14][15] riboflavin (B₂),^[16] niacin (B₃),^[17] biotin (B₇),^[18] and folic acid (B₉).^[19][20] In addition, each of the preceding studies further emphasizes that elevated consumption of beer and other ethanol-based drinks results in a net deficit of those B vitamins and the health risks associated with such deficiencies.

The B₁₂ vitamin is of note because it is not available from plant products, making B₁₂ deficiency a concern for vegans. 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.^[21]

Vitamin B may also be delivered by injection to reverse deficiencies.^[22]

Another popular means of increasing one's vitamin B intake is through the use of dietary supplements purchased at supermarkets, health centers, or natural food stores. B vitamins are also commonly added to energy drinks. Many energy drinks have been marketed with large amounts of B vitamins (5-Hour Energy contains 8333% of the recommended dietary allowance of vitamin B₁₂ and 2000% of the RDA for vitamin B₆. Many energy drinks offer "360% of the RDA for vitamin B₆, 120% of B₁₂, 140% of niacin (vitamin B₃)"^[23]) with claims that this will cause the consumer to "sail through your day without feeling jittery or tense." ^[23] Nutritionists, such as Case Western University Professor Hope Barkoukis, dismiss these claims: "It's brilliant marketing, but it doesn't have any basis [in fact]."^[23]

While B vitamins do "help unlock the energy in foods... just about everyone in America already gets all of the B vitamins they could possibly need in their diets... In general, extra B vitamins are just flushed out of the system, although everyone's limit of absorption is different in regards to B complex vitamins, and no-one knows how much is needed on an individual basis of these vitamins…"^[23] 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. Also, Vitamin B₉ (folic acid) 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 folic acid intake and/or take a supplement.^[24] However, for "most typical consumers of energy supplements or drinks, B vitamins are nothing more than a 'gimmick' when they are making these false claims."^[23]

Related nutrients

Many of the following substances have been referred to as vitamins because they were believed to be vitamins at one time, and they are relevant to vitamin nomenclature in that the numbers that were assigned to them form "gaps" in the series of B-vitamin names. Some of them, though not essential to humans, are essential in the diets of other organisms; others have no known nutritional value.

• Vitamin B₄: adenine, a nucleobase, is synthesized by the human body.^[25]
• Vitamin B₈: adenosine monophosphate, or alternately myo-inositol, is synthesized by the human body.
• Vitamin B₉: "vitamin I" of Centanni E. (1935)—also called "Enteral factor"—is a water and alcohol-soluble rice-bran factor that prevents digestive disturbance in pigeons. It governs the anatomical and functional integrity of the intestinal tract. Later found in yeast. Possible candidates for this substance are inositol, niacin (nicotinic acid), and biotin. Carnitine was also claimed to be a candidate but is not soluble in alcohol.
• Vitamin B₁₀: para-aminobenzoic acid (PABA)
• Vitamin B₁₁: pteryl-hepta-glutamic acid—chick growth factor, which is a form of folic acid. Later found to be one of five folates necessary for humans; also known as vitamin S or factor S. L-Carnitine is called vitamin B₁₁ in France.
• Vitamin B₁₃: orotic acid, now known to not be a vitamin.
• Vitamin B₁₄: cell proliferant, anti-anemia, rat growth, and antitumor pterin phosphate named by Earl R. Norris. Isolated from human urine at 0.33ppm (later in blood), but later abandoned by him as further evidence did not confirm this. He also claimed this was not xanthopterin.
• Vitamin B₁₅: pangamic acid
• Vitamin B₁₆: dimethylglycine (DMG)
• Vitamin B₁₇: nitrilosides, amygdalin or Laetrile. These substances are found in a number of seeds, sprouts, beans, tubers, and grains. While toxic in large quantities, proponents claim that it is effective in cancer treatment and prevention^[26] despite a lack of accepted scientific evidence.
• Vitamin B₁₈:
• Vitamin B₁₉:
• Vitamin B₂₀: carnitine
• Vitamin B₂₁:
• Vitamin B₂₂: often claimed as an ingredient of Aloe vera extracts but also in many other foods. Claimed by one source to be vitamin B₁₂b-δ.
• Vitamin B_h: biotin
• Vitamin B_m: "mouse factor": also used to designate inositol
• Vitamin B_p: choline Choline is only required for survival of some mutants. Most commonly it is synthesized in vivo de novo ^[27] May be added as supplement especially when methionine supply is limited.
• Vitamin B_t: L-carnitine
• Vitamin B_v: a type of B₆ but not pyridoxine
• Vitamin B_w: a type of biotin but not d-biotin
• Vitamin B_x: para-aminobenzoic acid

Note: B₁₆, B₁₇, B₁₈, B₁₉, B₂₀, B₂₁ & B₂₂ do not appear to be animal factors but are claimed by some naturopaths as human therapeutic factors.

References