The term vitamin B12 includes a group of related compounds called "cobalamins", including "hydroxocobalamin," adenosylcobalamin, "methylcobalamin" and "cyanocobalamin". This vitamin is used to criticize veganism because it is thought, generally, but inaccurately, that products of animal origin are the only source. In fact, active vitamin B12 is probably the only vitamin that is produced only by bacteria. The vitamin B12 is found in meat (especially offal), eggs and cow's milk from the activity of bacteria that live in animals. To be effectively absorbed through foods, the B12 is associated with many "molecular shuttles" that carry within the body. The vitamin combines with the first "shuttle" in the saliva during chewing. Then it is combined with a protein called intrinsic factor, which is produced by the stomach. Vitamin connects with the "intrinsic factor", which carries through the wall of the small intestine (ileum termial ") into the blood. There she is attached to another special protein which transports in all body tissues.
[...] "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials". Fam Pract 23 279–85. doi: 10.1093 /fampra/cml008. PMID 16585128. Andersson HC, Shapira E (1998). "Biochemical and clinical response to hydroxocobalamin versus cyanocobalamin treatment in patients with methylmalonic acidemia and homocystinuria (cblC)". J. Pediatr 121–4. doi: 10.1016 /S0022-3476(98)70496-2. PMID 9470012. Roze Gervais Demeret et al. (2003). "Neuropsychiatric disturbances in presumed late-onset cobalamin C disease". Arch. Neurol 1457–62. doi: 10.1001 /archneur PMID 14568819. Thauvin-Robinet Roze Couvreur et al. [...]
[...] If the rate of vitamin B12 between 100 and 500 pg / ml, is in the area of uncertainty and we must go further. The ideal is to measure methylmalonic acid and homocysteine in the blood. The concern is that the dosage in the blood of homocysteine is not reimbursed by social security and costs around 50 euros, while the determination of methylmalonic acid is repaid. The sensitivity for detecting a vitamin B12 deficiency by determination of methylmalonic acid alone was 98% in a population that does not include any from the only vegan. [...]
[...] Most were taking B12 pills or foods fortified with the vitamin are those who had the highest levels of vitamin in the blood. There were 3 patients who were vegan for 3 to 13 years (long enough to exhaust the reserves of the theoretical liver B12) that had no serious source of B12 in their diet, their levels in serum were 120 and 230pg / ml. All vegans were healthy, none showed symptoms of B12 deficiency and all had normal hemoglobin values. [...]
[...] The good intrinsic factor necessary for absorption of the vitamin, is known to be present in the small intestine, so if the bacteria also produce the B12 when they are inside the body, the vitamin can be absorbed. However just 1 molecule out of 30 like the B12, which has been found in human stool, was the active form of the vitamin, which may be more than sufficient for adequate intake - roughly 5µg per day - if it is produced in the small intestine where it can be absorbed. [...]
[...] The recommendations of B12 daily The references to nutritional vitamin B12 is 1.2 to 1.5 micrograms (mcg) daily for youth and adults and 2µg for breastfeeding women. The recommendation of 1.5 mg daily is intended to include a surplus to provide storage in the body to withstand a period of non-contribution. Recommendations for children are 0.3 to 0.4 mg, and for children aged 1 to 10 years, the reference nutrient intake begins to 0.5 mg and believes 1µg. The official recommendations have decreased in recent years, the body's needs had been previously overestimated. [...]
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