Essay On Vitamin B12

1. Andres E, Loukili NH, Noel E, Kaltenbach G, Abdelgheni MB, Perrin AE, et al. Vitamin B12 (cobalamin) deficiency in elderly patients. CMAJ. 2004;171(3):251–9.[PMC free article][PubMed]

2. Food and Nutrition Board, Institute of Medicine. Dietary reference intakes for thiamine, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. Washington, DC: National Academy Press; 1998. [PubMed]

3. Allen LH. Folate and vitamin B12 status in the Americas. Nutr Rev. 2004;62(6 Pt 2):S29–33.[PubMed]

4. Gupta AK, Damji A, Uppaluri A. Vitamin B12 deficiency. Prevalence among South Asians at a Toronto clinic. Can Fam Physician. 2004;50:743–7.[PMC free article][PubMed]

5. Canadian Task Force on Preventive Health Care. CTFPHC systematic reviews and recommendations. London, ON: Canadian Task Force on Preventive Health Care; [Accessed 2007 August 23]. Available from:

6. Schwammenthal Y, Tanne D. Homocysteine, B-vitamin supplementation, and stroke prevention: from observational to interventional trials. Lancet Neurol. 2004;3:493–5.[PubMed]

7. Stanger O, Herrmann W, Pietrzik K, Fowler B, Geisel J, Dierkes J, et al. DACH-LIGA homocysteine (German, Austrian and Swiss homocysteine society): consensus paper on the rational clinical use of homocysteine, folic acid and B-vitamins in cardiovascular and thrombotic diseases: guidelines and recommendations. Clin Chem Lab Med. 2003;41:1392–403.[PubMed]

8. Lee BJ, Huang MC, Chung LJ, Cheng CH, Lin KL, Su KH, et al. Folic acid and vitamin B12 are more effective than vitamin B6 in lowering fasting plasma homocysteine concentration in patients with coronary artery disease. Eur J Clin Nutr. 2004;58:481–7.[PubMed]

9. Lewerin C, Nilsson-Ehle H, Matousek M, Lindstedt G, Steen B. Reduction of plasma homocysteine and serum methymalonate concentrations in apparently healthy elderly subjects after treatment with folic acid, vitamin B12 and vitamin B6: a randomized trial. Eur J Clin Nutr. 2003;57:1426–36.[PubMed]

10. Wulffele MG, Kooy A, Lehert P, Bets D, Ogterop JC, Borger van der Burg B, et al. Effects of short-term treatment with metformin on serum concentrations of homocysteine, folate and vitamin B12 in type 2 diabetes mellitus: a ran-domised, placebo-controlled trial. J Intern Med. 2004;254:455–63.[PubMed]

11. Polkinghorne KR, Zoungas S, Branley P, Villanueva E, McNeil JJ, Atkins RC, et al. Randomized, placebo-controlled trial of intramuscular vitamin B12 for the treatment of hyperhomocysteinemia in dialysis patients. Intern Med J. 2003;33:489–94.[PubMed]

12. Sombolos K, Fragia T, Natse T, Bartholomatos G, Karagianni A, Katsaris G, et al. The effect of long-term intravenous high dose B-complex vitamins with or without folic acid on serum homocysteine in hemodialysis patients. J Nephrol. 2002;15:671–5.[PubMed]

13. Chery C, Barbe F, Lequere C, Abdelmouttaleb I, Gerard P, Barbarino P, et al. Hyperhomocysteinemia is related to a decreased blood level of vitamin B12 in the second and third trimester of normal pregnancy. Clin Chem Lab Med. 2002;40:1105–8.[PubMed]

14. Medrano MJ, Sierra MJ, Almazán J, Olalla MT, López-Abente G. The association of dietary folate, B6, and B12 with cardiovascular mortality in Spain: an ecological analysis. Am J Public Health. 2000;90:1636–8.[PMC free article][PubMed]

15. He K, Merchant A, Rimm EB, Rosner BA, Stampfer MJ, Willett WC, et al. Folate, vitamin B6, and B12 intakes in relation to risk of stroke among men. Stroke. 2004;35:169–74.[PubMed]

16. Quinlivan EP, McPartlin J, McNulty H, Ward M, Strain JJ, Weir DG, et al. Importance of both folic acid and vitamin B12 in reduction of risk of vascular disease. Lancet. 2002;359:227–8.[PubMed]

17. Tan NC, Venketasubramanian N, Saw SM, Tjia HT. Hyperhomocyst(e)inemia and risk of ischemic stroke among young Asian adults. Stroke. 2002;33:1956–62.[PubMed]

18. Undas A, Domagala TB, Jankowski M, Szezeklik A. Treatment of hyperho-mocysteinemia with folic acid and vitamins B12 and B6 attenuates thrombin generation. Thromb Res. 1999;95:281–8.[PubMed]

19. Lonn E, Yusuf S, Arnold MJ, Sheridan P, Pogue J, Micks M, et al. Homocysteine lowering with folic acid and B vitamins in vascular disease. N Engl J Med. 2006;354(15):1567–77.[PubMed]

20. Bonaa KH, Njolstad I, Ueland PM, Schirmer H, Tverdal A, Steigen T, et al. Homocysteine lowering and cardiovascular events after acute myocardial infarction. N Engl J Med. 2006;354(15):1578–88.[PubMed]

21. Dusitanond P, Eikelboom JW, Hankey GJ, Thom J, Gilmre G, Loh K, et al. Homocysteine-lowering treatment with folic acid, cobalamin, and pyridoxine does not reduce blood markers of inflammation, endothelial dysfunction, or hypercoagulability in patients with previous transient ischemic attack or stroke: a randomized substudy of the VITATOPS trial. Stroke. 2005;36:144–6.[PubMed]

22. Setola E, Monti LD, Galluccio E, Palloshi A, Fragasso G, Paroni R, et al. Insulin resistance and endothelial function are improved after folate and vitamin B12 therapy in patients with metabolic syndrome: relationship between homocysteine levels and hyperinsulinemia. Eur J Endocrinol. 2004;151:483–9.[PubMed]

23. Jonasson T, Ohlin AK, Gottsäter A, Hultberg B, Ohlin H. Plasma homocys-teine and markers for oxidative stress and inflammation in patients with coronary artery disease—a prospective randomized study of vitamin supplementation. Clin Chem Lab Med. 2005;43:628–34.[PubMed]

24. Ullegaddi R, Powers HJ, Gariballa SE. Antioxidant supplementation with or without B-group vitamins after acute ischemic stroke: a randomized controlled trial. J Parenter Enteral Nutr. 2006;30:108–14.[PubMed]

25. Den Heijer M, Willems HP, Blom HJ, Gerrits WB, Cattaneo M, Eichinger S, et al. Homocysteine lowering by B vitamins and the secondary prevention of deep vein thrombosis and pulmonary embolism: a randomized, placebo-controlled, double-blind trial. Blood. 2007;109:139–44.[PubMed]

26. Ray JG, Kearon C, Yi Q, Sheridan P, Lonn E Heart Outcomes Prevention Evaluation 2 (HOPE-2) Investigators. Homocysteine-lowering therapy and risk for venous thromboembolism: a randomized trial. Ann Intern Med. 2007;146:761–7.[PubMed]

27. Bleys J, Miller ER, 3rd, Pastor-Barriuso R, Appel LJ, Guallar E. Vitamin-mineral supplementation and the progression of atherosclerosis: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2006;84:880–7.[PubMed]

28. Ames BN. DNA damage from micronutrient deficiencies is likely to be a major cause of cancer. Mutat Res. 2001;475:7–20.[PubMed]

29. Alberg AJ, Selhub J, Shah KV, Viscidi RP, Comstock GW, Helzlsouer KJ. The risk of cervical cancer in relation to serum concentrations of folate, vitamin B12, and homocysteine. Cancer Epidemiol Biomarkers Prev. 2000;9:761–4.[PubMed]

30. Hernandez BY, McDuffie K, Wilkens LR, Kamemoto L, Goodman MT. Diet and premalignant lesions of the cervix: evidence of a protective role for folate, riboflavin, thiamin, and vitamin B12. Cancer Causes Control. 2003;14:859–70.[PubMed]

31. Slattery ML, Potter JD, Samowitz W, Schaffer D, Leppert M. Methylenete trahydrofolate reductase, diet, and risk of colon cancer. Cancer Epidemiol Biomarkers Prev. 1999;8:513–8.[PubMed]

32. Chen J, Giovannucci E, Hankinson SE, Ma J, Willett WC, Spiegelman D, et al. A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms, and risk of colorectal adenoma. Carcinogenesis. 1998;19:2129–32.[PubMed]

33. Ma J, Stampfer MJ, Christensen B, Giovannucci E, Hunter DJ, Chen J, et al. A polymorphism of the methionine synthase gene: association with plasma folate, vitamin B12, homocyst(e)ine, and colorectal cancer risk. Cancer Epidemiol Biomarkers Prev. 1999;8:825–9.[PubMed]

34. Teunissen CE, Blom AH, Van Boxtel MP, Bosma H, de Bruijn C, Jolles J, et al. Homocysteine: a marker for cognitive performance? A longitudinal follow-up study. J Nutr Health Aging. 2003;7:153–9.[PubMed]

35. Clarke R, Harrison G, Richards S Vital Trial Collaborative Group. Effect of vitamins and aspirin on markers of platelet activation, oxidative stress and homocysteine in people at high risk of dementia. J Intern Med. 2003;254:67–75.[PubMed]

36. Hassing L, Wahlin A, Winblad B, Backman L. Further evidence on the effects of vitamin B12 and folate levels on episodic memory functioning: a population-based study of healthy very old adults. Biol Psychiatry. 1999;45:1472–80.[PubMed]

37. Nilsson K, Warkentin S, Hultberg B, Faldt R, Gustafson L. Treatment of cobalamin deficiency in dementia, evaluated clinically and with cerebral blood flow measurements. Aging. 2000;12:199–207.[PubMed]

38. Eastley R, Wilcock GK, Bucks RS. Vitamin B12 deficiency in dementia and cognitive impairment: the effects of treatment on neuropsychological function. Int J Geriatr Psychiatry. 2000;15:226–33.[PubMed]

39. Malouf R, Areosa Sastre A. Vitamin B12 for cognition. Cochrane Database Syst Rev. 2003;(3):CD004326.[PubMed]

40. Meins W, Muller-Thomsen T, Meier-Baumgartner HP. Subnormal serum vitamin B12 and behavioural and psychological symptoms in Alzheimer’s disease. Int J Geriatr Psychiatry. 2000;15:415–8.[PubMed]

41. Engelborghs S, Vloeberghs E, Maertens K, Mariën P, Somers N, Symons A, et al. Correlations between cognitive, behavioural and psychological findings and levels of vitamin B12 and folate in patients with dementia. Int J Geriatr Psychiatry. 2004;19:365–70.[PubMed]

42. Clarke R, Grimley Evans J, Schneede J, Nexo E, Bates C, Fletcher A, et al. Vitamin B12 and folate deficiency in later life. Age Ageing. 2004;33:34–41.[PubMed]

43. Tiemeier H, van Tuiji HR, Hofman A, Meijer J, Kiliaan AJ, Breteler MM. Vitamin B12, folate, and homocysteine in depression: the Rotterdam Study. Am J Psychiatry. 2002;159:2099–101.[PubMed]

44. Bjelland I, Tell GS, Vollset SE, Refsum H, Ueland PM. Folate, vitamin B12, homocysteine, and the MTHFR 677C→T polymorphism in anxiety and depression: the Hordalund Homocysteine Study. Arch Gen Psychiatry. 2003;60:618–26.[PubMed]

45. Hintikka J, Tolmunen T, Tanskanen A, Viinamäki H. High vitamin B12 level and good treatment outcome may be associated in major depressive disorder. BMC Psychiatry. 2003;3:17–22.[PMC free article][PubMed]

46. Hvas AM, Juul S, Lauritzen L, Nexø E, Ellegaard J. No effect of vitamin B-12 treatment on cognitive function and depression: a randomized placebo controlled study. J Affect Disord. 2004;81:269–73.[PubMed]

47. Stott DJ, MacIntosh G, Lowe GD, Rumley A, McMahon AD, Langhorne P, et al. Randomized controlled trial of homocysteine-lowering vitamin treatment in elderly patients with vascular disease. Am J Clin Nutr. 2005;82:1320–6.[PubMed]

48. McMahon JA, Green TJ, Skeaff CM, Knight RG, Mann JI, Williams SM. A controlled trial of homocysteine lowering and cognitive performance. N Engl J Med. 2006;354(26):2764–72.[PubMed]

49. Eussen SJ, de Groot LC, Joosten LW, Bloo RJ, Clarke R, Ueland PM, et al. Effect of oral vitamin B-12 with or without folic acid on cognitive function in older people with mild vitamin B-12 deficiency: a randomized, placebo- controlled trial. Am J Clin Nutr. 2006;84:361–70.[PubMed]

50. Ray JG, Meier C, Vermeulen MJ, Boss S, Wyatt PR, Cole DE. Association of neural tube defects and folic acid food fortification in Canada. Lancet. 2002;360:2047–8.[PubMed]

51. Refsum H. Folate, vitamin B12 and homocysteine in relation to birth defects and pregnancy outcome. Br J Nutr. 2001;85(Suppl 2):S109–13.[PubMed]

52. Ray JG, Blom HJ. Vitamin B12 insufficiency and the risk of neural tube defects. QJM. 2003;96:289–95.[PubMed]

53. Wilson A, Platt R, Wu Q, Leclerc D, Christensen B, Yang H, et al. A common variant in methionine synthase reductase combined with low cobalamin (vitamin B12) increases risk for spina bifida. Mol Genet Metab. 1999;67:317–23.[PubMed]

54. Gueant-Rodriguez RM, Rendeli C, Namour B, Venuti L, Romano A, Anello G, et al. Transcobalamin and methionine synthase reductase mutated polymorphisms aggravate the risk of neural tube defects in humans. Neurosci Lett. 2003;344:189–92.[PubMed]

55. Afman LA, Van Der Put NMJ, Thomas CMG, Trijbels JMF, Blom HJ. Reduced vitamin B12 binding by transcobalamin II increases the risk of neural tube defects. QJM. 2001;94:159–66.[PubMed]

56. Gueant JL, Gueant-Rodriguez RM, Anello G, Bosco P, Brunaud L, Romano C, et al. Genetic determinants of folate and vitamin B12 metabolism: a common pathway in neural tube defect and Down syndrome? Clin Chem Lab Med. 2003;41:1473–7.[PubMed]

B vitamins are a class of water-soluble vitamins that play important roles in cellmetabolism. Though these vitamins share similar names, research shows that they are chemically distinct vitamins that often coexist in the same foods. In general, dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific number or name of each vitamin: B1 = thiamine, B2 = riboflavin, B3 = niacin, etc. Some are better known by name than number: niacin, pantothenic acid, biotin and folate.

Each B vitamin is either a cofactor (generally a coenzyme) for key metabolic processes or is a precursor needed to make one.

List of B vitamins[edit]

B number  NameThumbnail description
Vitamin B1thiamineA coenzyme in the catabolism of sugars and amino acids.
Vitamin B2riboflavinA precursor of cofactors called FAD and FMN, which are needed for flavoprotein enzyme reactions, including activation of other vitamins
Vitamin B3niacin (nicotinic acid), nicotinamide ribosideA precursor of coenzymes called NAD and NADP, which are needed in many metabolic processes.
Vitamin B5pantothenic acidA precursor of coenzyme A and therefore needed to metabolize many molecules.
Vitamin B6pyridoxine, pyridoxal, pyridoxamineA coenzyme in many enzymatic reactions in metabolism.
Vitamin B7biotinA coenzyme for carboxylase enzymes, needed for synthesis of fatty acids and in gluconeogenesis.
Vitamin B9folateA precursor needed to make, repair, and methylate DNA; a cofactor in various reactions; especially important in aiding rapid cell division and growth, such as in infancy and pregnancy. Synthetic folate is known as folic acid.
Vitamin B12various cobalamins; commonly cyanocobalamin or methylcobalamin in vitamin supplementsA coenzyme involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid metabolism and amino acid metabolism.

Note: other substances once thought to be vitamins were given numbers in the B-vitamin numbering scheme, but were subsequently discovered to be either not essential for life or manufactured by the body, thus not meeting the two essential qualifiers for a vitamin. See section #Related compounds for numbers 4, 8, 10, 11, and others.

B vitamin molecular functions[edit]

VitaminNameStructureMolecular Function
Vitamin B1thiamineThiamine plays a central role in the release of energy from carbohydrates. It is involved in RNA and DNA production, as well as nerve function. Its active form is a coenzyme called thiamine pyrophosphate (TPP), which takes part in the conversion of pyruvate to acetyl coenzyme A (CoA) in metabolism.[1]
Vitamin B2riboflavinRiboflavin is involved in release of energy in the electron transport chain, the citric acid cycle, as well as the catabolism of fatty acids (beta oxidation).[2][unreliable medical source?]
Vitamin B3niacin
Niacin is composed of two structures: nicotinic acid and nicotinamide. There are two co-enzyme forms of niacin: nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Both play an important role in energy transfer reactions in the metabolism of glucose, fat and alcohol.[3]

NAD carries hydrogens and their electrons during metabolic reactions, including the pathway from the citric acid cycle to the electron transport chain. NADP is a coenzyme in lipid and nucleic acid synthesis.[4]

Vitamin B5pantothenic acidPantothenic acid is involved in the oxidation of fatty acids and carbohydrates. Coenzyme A, which can be synthesised from pantothenic acid, is involved in the synthesis of amino acids, fatty acids, ketone bodies, cholesterol,[5] phospholipids, steroid hormones, neurotransmitters (such as acetylcholine), and antibodies.[6]
Vitamin B6pyridoxine, pyridoxal, pyridoxamineThe active form pyridoxal 5'-phosphate (PLP) (depicted) serves as a cofactor in many enzyme reactions mainly in amino acid metabolism including biosynthesis of neurotransmitters.
Vitamin B7biotinBiotin plays a key role in the metabolism of lipids, proteins and carbohydrates. It is a critical co-enzyme of four carboxylases: acetyl CoA carboxylase, which is involved in the synthesis of fatty acids from acetate; pyruvate CoA carboxylase, involved in gluconeogenesis; β-methylcrotonyl CoA carboxylase, involved in the metabolism of leucine; and propionyl CoA carboxylase, which is involved in the metabolism of energy, amino acids and cholesterol.[7]
Vitamin B9folateFolate acts as a co-enzyme in the form of tetrahydrofolate (THF), which is involved in the transfer of single-carbon units in the metabolism of nucleic acids and amino acids. THF is involved in pyrimidine nucleotide synthesis, so is needed for normal cell division, especially during pregnancy and infancy, which are times of rapid growth. Folate also aids in erythropoiesis, the production of red blood cells.[8]
Vitamin B12cobalaminVitamin B12 is involved in the cellular metabolism of carbohydrates, proteins and lipids. It is essential in the production of blood cells in bone marrow, and for nerve sheaths and proteins.[9] Vitamin B12 functions as a co-enzyme in intermediary metabolism for the methionine synthase reaction with methylcobalamin, and the methylmalonyl CoA mutase reaction with adenosylcobalamin.[10][not in citation given]

B vitamin deficiency[edit]

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.

VitaminNameDeficiency effects
Vitamin B1thiamineDeficiency causes beriberi. Symptoms of this disease of the nervous system include weight loss, emotional disturbances, Wernicke's encephalopathy (impaired sensory perception), weakness and pain in the limbs, periods of irregular heartbeat, and edema (swelling of bodily tissues). Heart failure and death may occur in advanced cases. Chronic thiamin deficiency can also cause Korsakoff's syndrome, an irreversible dementia characterized by amnesia and compensatory confabulation.
Vitamin B2riboflavin

Main article: Riboflavin § Deficiency

Deficiency causes ariboflavinosis. Symptoms may include cheilosis (cracks in the lips), high sensitivity to sunlight, angular cheilitis, glossitis (inflammation of the tongue), seborrheic dermatitis or pseudo-syphilis (particularly affecting the scrotum or labia majora and the mouth), pharyngitis (sore throat), hyperemia, and edema of the pharyngeal and oralmucosa.
Vitamin B3niacinDeficiency, along with a deficiency of tryptophan causes pellagra. Symptoms include aggression, dermatitis, insomnia, weakness, mental confusion, and diarrhea. In advanced cases, pellagra may lead to dementia and death (the 3(+1) D's: dermatitis, diarrhea, dementia, and death).
Vitamin B5pantothenic acidDeficiency can result in acne and paresthesia, although it is uncommon.
Vitamin B6pyridoxine, pyridoxal, pyridoxamine

Main article: Vitamin B6 § Deficiency

seborrhoeic dermatitis-like eruptions, pink eye, neurological symptoms (e.g. epilepsy)
Vitamin B7biotinDeficiency does not typically cause symptoms in adults but may lead to impaired growth and neurological disorders in infants. Multiple carboxylase deficiency, an inborn error of metabolism, can lead to biotin deficiency even when dietary biotin intake is normal.
Vitamin B9folic acidDeficiency results in a macrocytic anemia, and elevated levels of homocysteine. Deficiency in pregnant women can lead to birth defects.
Vitamin B12cobalaminDeficiency results in a macrocytic anemia, elevated methylmalonic acid and homocysteine, peripheral neuropathy, memory loss and other cognitive deficits. It is most likely to occur among elderly people, as absorption through the gut declines with age; the autoimmune disease pernicious anemia is another common cause. It can also cause symptoms of mania and psychosis. In rare extreme cases, paralysis can result.


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

VitaminNameTolerable Upper Intake Level (UL)Harmful effects
Vitamin B1thiamineNone[11]No known toxicity from oral intake. There are some reports of anaphylaxis caused by high-dose thiamin injections into the vein or muscle. However, the doses were greater than the quantity humans can physically absorb from oral intake.[11]
Vitamin B2riboflavinNone.[12]No evidence of toxicity based on limited human and animal studies. The only evidence of adverse effects associated with riboflavin comes from in vitro studies showing the production of reactive oxygen species (free radicals) when riboflavin was exposed to intense visible and UV light.[12]
Vitamin B3niacinU.S. UL = 35 mg as a dieatry supplement[13]Intake of 3000 mg/day of nicotinamide and 1500 mg/day of nicotinic acid are associated with nausea, vomiting, and signs and symptoms of liver toxicity. Other effects may include glucose intolerance, and (reversible) ocular effects. Additionally, the nicotinic acid form may cause vasodilatory effects, also known as flushing, including redness of the skin, often accompanied by an itching, tingling, or mild burning sensation, which is also often accompanied by pruritus, headaches, and increased intracranial blood flow, and occasionally accompanied by pain.[13] Medical practitioners prescribe recommended doses up to 2000 mg per day of niacin in either immediate-release or slow-release formats, to lower plasma triglycerides and low-density lipiprotein cholesterol.[14]
Vitamin B5pantothenic acidNoneNo toxicity known
Vitamin B6pyridoxine, pyridoxal, pyridoxamineU.S. UL = 100 mg/day; EU UL = 25 mg/day

Main article: vitamin B6 § Side effects

Main article: vitamin B6 § Side effects

Vitamin B7biotinNoneNo toxicity known
Vitamin B9folic acid1 mg/day[15]Masks B12 deficiency, which can lead to permanent neurological damage[15]
Vitamin B12cyanocobalaminNone established.[16]Skin and spinal lesions. Acne-like rash [causality is not conclusively established].[16][17]

B vitamin sources[edit]

B vitamins are found in whole unprocessed foods. Processed carbohydrates such as sugar and white flour tend to have lower B vitamin than their unprocessed counterparts. For this reason, it is required by law in many countries (including the United States) that the B vitamins thiamine, riboflavin, niacin, and folic acid be added back to white flour after processing. This is sometimes called "Enriched Flour" on food labels. B vitamins are particularly concentrated in meat such as turkey, tuna and liver.[18] Good sources for B vitamins include legumes (pulses or beans), whole grains, potatoes, bananas, chili peppers, tempeh, nutritional yeast, brewer's yeast, and molasses. Although the yeast used to make beer results in beers being a source of B vitamins,[19] their bioavailability ranges from poor to negative as drinking ethanol inhibits absorption of thiamine (B1),[20][21] riboflavin (B2),[22] niacin (B3),[23] biotin (B7),[24] and folic acid (B9).[25][26] In addition, each of the preceding studies further emphasizes that elevated consumption of beer and other alcoholic beverages results in a net deficit of those B vitamins and the health risks associated with such deficiencies.

The B12 vitamin is not available from plant products, making B12 deficiency a legitimate concern for vegans.[citation needed] 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.[27]

A popular way of increasing one's vitamin B intake is through the use of dietary supplements. B vitamins are commonly added to energy drinks, many of which have been marketed with large amounts of B vitamins[28] with claims that this will cause the consumer to "sail through your day without feeling jittery or tense."[28] Some nutritionists have been critical of these claims, pointing out for instance that while B vitamins do "help unlock the energy in foods," most Americans acquire the necessary amounts easily in their diets.[28]

Because they are soluble in water, excess B vitamins are generally readily excreted, although individual absorption, use and metabolism may vary…"[28] 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.[medical citation needed] In cases of severe deficiency, B vitamins, especially B12, may also be delivered by injection to reverse deficiencies.[29][unreliable medical source?] 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.[30] 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.[31]

B vitamin discovery dates[edit]

Related compounds[edit]

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 (e.g., 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.[32][33] Choline is synthesized by the human body, but not sufficiently to maintain good health, and is now considered an essential dietary nutrient.[34] Adenine is a nucleobase synthesized by the human body.[35] Carnitine is an essential dietary nutrient for certain worms, but not for humans.[36]
  • Vitamin B8: adenosine monophosphate (AMP), also known as adenylic acid.[37] Vitamin B8 may also refer to inositol.[38]
  • Vitamin B10: para-aminobenzoic acid (pABA or PABA), a chemical component of the folate molecule produced by plants and bacteria, and found in many foods.[39][40] It is best known as a UV-blocking sunscreen applied to the skin, and is sometimes taken orally for certain medical conditions.[39][41]
  • Vitamin B11: pteryl-hepta-glutamic acid (PHGA; chick growth factor). Vitamin Bc-conjugate was also found to be identical to PHGA.[citation needed]
  • Vitamin B13: orotic acid.[42]
  • Vitamin B14: cell proliferant, anti-anemia, rat growth factor, 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,[42] also known as pangamate. Promoted in various forms as a dietary supplement and drug; considered unsafe and subject to seizure by the US Food and Drug Administration.[43]
  • Vitamin B16: dimethylglycine (DMG)[44] is synthesized by the human body from choline.
  • Vitamin B17: pseudoscientific name for the poisonous compound amygdalin, also known as the equally pseudoscientific name "nitrilosides" despite the fact that it is a single compound. Amygdalin can be found in various plants, but is most commonly extracted from apricot pits and other similar fruit kernels. Amygdalin is hydrolyzed by various intestinal enzymes to form, among other things, hydrogen cyanide, which is toxic to human beings when exposed to a high enough dosage. Some proponents claim that amygdalin is effective in cancer treatment and prevention, despite its toxicity and a severe lack of scientific evidence.[45]
  • Vitamin B20: L-carnitine.[44]
  • Vitamin Bf: carnitine.[37]
  • Vitamin Bm: myo-inositol, also called "mouse antialopaecia factor".[46]
  • Vitamin Bp: "antiperosis factor", which prevents perosis, a leg disorder, in chicks; can be replaced by choline and manganese salts.[36][37][47]
  • Vitamin BT: carnitine.[48][36]
  • Vitamin Bv: a type of B6 other than pyridoxine.
  • Vitamin BW: a type of biotin other than d-biotin.
  • Vitamin Bx: an alternative name for both pABA (see vitamin B10) and pantothenic acid.[36][41]


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