Vitamin B12 is an essential vitamin, needed for proper development and functioning of the nervous system. A deficiency in vitamin B12 can lead to weight loss, constipation, and anemia. Numbness (tingling) in hands and feet may also occur in addition to depression, dementia, and memory loss.
Since vitamin B12 is naturally found only in animal foods, vegetarians are considered an at-risk group for vitamin B12 deficiency. Fortunately, a wide variety of plant foods are fortified with vitamin B12. Further dairy, eggs, and cheese are all good natural sources of vitamin B12.
Vegetarian foods high in vitamin B12 include fortified cereals, fortified fruit juices, fortified tofu, yogurt, milk, cheese, eggs, vitamin water, and whey powder. The daily value for vitamin B12 is 6μg per day, this is about 3 times the recommended daily allowance of 2.4μg per day to be sure everyone gets enough vitamin B12.
Since vitamin B12 is well regulated by the body, and stores of vitamin B12 can be accumulated in the liver, there is no tolerable upper intake for vitamin B12.
Specific brands high in vitamin B12 (%DV per 8oz cup)
Naked Blue Machine (100% DV), Bolthouse Farms Daily Greens (44% DV), Bolthouse Farms Berry Boost (38% DV). As with all fortified foods, the amount of vitamin B12 can vary, check labels for specific amounts.
The recommended daily allowance (RDA) for Vitamin B12 ranges from 0.4 to 2.8μg per day. This is quite a bit lower than the daily value (%DV) of 6μg. The daily value (%DV) is higher since excess vitamin B12 is well tolerated by the body, and so that certain groups with a risk of deficiency get plenty of vitamin B12 in their diet. Further, the daily value is also often higher than the RDA to account for absorption factors that can occur in a diverse diet.
For the values above the amounts for children less than 12 months old is actually the adequate intake (AI) not RDA.
Which form vitamin B12 is best?
Cyanocobalamin is the most common synthetic form of vitamin B12. However, methylcobalamin may also be used. Current evidence does not suggest one form is better than the other, so any form of added B12 can be considered to be equally effective.2
What is intrinsic factor and how does it affect vitamin B12 absorption?
Intrinsic factor can be thought of as "absorption chemicals" in your gut needed for absorption of vitamin B12. Your body only creates and secretes a limited amount of intrinsic factor. So despite consuming supplements or fortified foods, only limited amounts of vitamin B12 will be absorbed by your body. As such you might only absorb 10μg of a 500μg supplement.2
Due to this factor, sometimes vitamin B12 is injected directly into patients, as opposed to supplements taken orally. These vitamin B12 injections can be a faster way to boost vitamin B12 levels and alleviate symptoms from anemia.
What are the health benefits of Vitamin B12?
Protection Against Heart Disease - Adequate levels of vitamins B12, B6, and B9 have been shown to lower levels of a protein in the blood: homocysteine. Lower levelsof homocysteine has been shown to improve endothelial function, which in turn may boost cardiovascular health and decrease risk of heartattacks.3-5
Protection and Repair of DNA to Reduce Cancer Risk and Slow Aging - Absorption of vitamin b12 and Folate (B9) is essential for DNA metabolism and maintenance whichhelps to prevent cancer and slow aging.6
Protection Against Dementia and Cognitive Decline - Lack of vitamin B12 increases homocysteine levels, which in turn decreases the bodies ability to metabolize neurotransmitters.7 Due to limitations with creating long term controlled studies in human populations, no definite link between increased vitamin b12 levels and cognitive function have been found,8-12 however several observational studies suggest increased homocysteine levels increase the incidence of Alzheimer's disease and dementia,13-15 and low levels of vitamin B12 has been associated with cognitive decline.16
Alzheimer's Protection - A study has shown that a deficiency in Vitamin B12 and Folate (B9) can double the risk of Alzheimer's Disease.17
Energy and Endurance - A lack of vitamin B12 will lead to anemia and weakness. Adequate levels of vitamin B12 are necessary to maintain normal energy levels. Claims of vitamin B12 as an energy or atheletic enhancer remain unproven.18
Does Cyanocobalamin Contain Cyanide?
Cyanocobalamin is a common synthetic form of vitamin B12 used in supplements and fortified foods. While cyanide is present in this form of vitamin b12, it is not present in large enough amounts to be dangerous and is excreted by the body. Numerous other foods naturally contain cyanide, including almonds, lima beans, and spinach.
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Cows are not given any form of synthetic vitamin b12. Vitamin b12 is actually naturally synthesized by bacteria that flourish in certain animals (most animals actually, just not humans). Cows, in particular, ferment their food in 4 different stomachs as they digest it. This fermentation lets the bacteria in cows create vitamin b12, and allows cows to store any excess vitamin b12.
As in the article on vegan b12 foods, some fermented foods like beer or wine will also sometimes contain vitamin b12.
Despite the letter "B" in vitamin B12 the nutrient does not confer any coloration to foods. The blue color found in fruits, like blueberries, comes from the anthocyanins found in blueberries.
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Data Sources and References
USDA National Nutrient Database for Standard Reference, Release 28.
Doshi SN, McDowell IF, Moat SJ, Payne N, Durrant HJ, Lewis MJ, Goodfellos J. Folic acid improves endothelial function in coronary artery disease via mechanisms largely independent of homocysteine. Circulation. 2002;105:22-6.
Doshi SN, McDowell IFW, Moat SJ, Lang D, Newcombe RG, Kredean MB, Lewis MJ, Goodfellow J. Folate improves endothelial function in coronary artery disease. Arterioscler Thromb Vasc Biol 2001;21:1196-1202.
Wald DS, Bishop L, Wald NJ, Law M, Hennessy E, Weir D, McPartlin J, Scott J. Randomized trial of folic acid supplementation and serum homocysteine levels. Arch Intern Med 2001;161:695-700.
A Paoloni-Giacobino, R Grimble, C Pichard. Genetics and nutrition. Clinical Nutrition Volume 22, Issue 5, Pages 429-435 (October 2003)
Hutto BR. Folate and cobalamin in psychiatric illness. Compr Psychiatry 1997;38:305-14.
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.
Hvas AM, Juul S, Lauritzen L, Nexo 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.
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.
Kang JH, Cook N, Manson J, Buring JE, Albert CM, Grodstein F. A trial of B vitamins and cognitive function among women at high risk of cardiovascular disease. Am J Clin Nutr 2008;88:1602-10.
Aisen PS, Schneider LS, Sano M, Diaz-Arrastia R, van Dyck CH, Weiner MF, et al.; Alzheimer Disease Cooperative Study. High-dose B vitamin supplementation and cognitive decline in Alzheimer disease: a randomized controlled trial. JAMA 2008 ;300:1774-83.
Clarke R. B-vitamins and prevention of dementia. Proc Nutr Soc 2008;67:75-81.
Schulz RJ. Homocysteine as a biomarker for cognitive dysfunction in the elderly. Curr Opin Clin Nutr Metab Care 2007;10:718-23.
Seshadri S, Beiser A, Selhub J, Jacques PF, Rosenberg IH, D'Agostino RB, et al. Plasma homocysteine as a risk factor for dementia and Alzheimer's disease. N Engl J Med 2002;346:476-83.
Clarke R, Birks J, Nexo E, Ueland PM, Schneede J, Scott J, et al. Low vitamin B-12 status and risk of cognitive decline in older adults. Am J Clin Nutr 2007;86:1384-91.
Wang HX, Wahlin A, Basun H, Fastbom J, Winblad B, Fratiglioni L. Vitamin B12 and folate in relation to the development of Alzheimer?s disease. Neurology May 8, 2001 vol. 56 no. 9 1188-1194.
Lukaski HC. Vitamin and mineral status: effects on physical performance. Nutrition 2004;20:632-44.
Patrick Kidd and David L. Mollin. Megaloblastic Anaemia and Vitamin-B12 Deficiency After Anticonvulsant Therapy. Br Med J. 1957 October 26; 2(5051): 974?976.
J.S. MALPAS, G.H. SPRAY, L.J. WITTS. Serum Folic-acid and Vitamin-Biz Levels in Anticonvulsant Therapy. British Medical Journal. 16 April 1966.
Richard Hunterb, Joanna Barnesb, and D. M. Matthews. EFFECT OF FOLIC-ACID SUPPLEMENT ON SERUM-VITAMIN-B12 LEVELS IN PATIENTS ON ANTICONVULSANTS. The Lancet, Volume 294, Issue 7622, 27 September 1969, Pages 666-667.