Vitamin B₁₂ is not found in plants, but it is produced by bacteria in the digestive tract of animals, which explains why animal protein products are the only dietary source of this nutrient. Organ meats are the best source of vitamin B₁₂, followed by clams, oysters, beef, eggs, milk, chicken and cheese.

Interactions

Drug/Nutrient Depletions • Oral contraceptives • Antibiotics • Antivirals Nucleoside Reverse Transcriptase Inhibitors • Biguanides • Bile acid sequestrants • clofibrate • colchicine • H-2 receptor antagonists • phenytoin • Proton pump inhibitors • Potassium chloride, sustained / controlled release medications

One of the most important long-term benefits of vitamin B12 is the role it plays in preventing elevated levels of homocysteine from building up in the body even when the levels are increased by lipid lowering drugs known as fibrates.(1, 2, 3) Homocysteine is actually a toxic substance that is formed during the metabolism of the amino acid methionine. Vitamin B12 is one of the vitamins that is required to convert homocysteine into a non-toxic compound. Elevated homocysteine increases the risk of developing atherosclerosis.(4) Also, vitamin B12 deficiency may occur in strict vegetarians which could increase the risk of hyperhomocysteinaemia.(5)

Studies involving hundreds of patients who had undergone successful coronary angioplasty have evaluated these individuals following six months of therapy on vitamin B6, vitamin B12 and folic acid, comparing the results to patients on placebo. After one year, the patients on the vitamin therapy had lower rates of related cardiovascular events including heart attacks and repeated angioplasty.(6, 7)

Dietary supplementation with the B-vitamins prevented hyperhomocysteinemia but did not prevent the development of vascular dysfunction or atherosclerotic lesions.(8)

Studies have shown cognitive skills such as knowing, thinking, learning and judging can be impaired in older adults with low levels of certain B vitamins. Supplementation with folate, vitamin B12 and vitamin B6 has been effective in enhancing cognitive performance in older adults.(9) In fact, one study in older adults noted that subjects with low levels of vitamin B12 or folate had twice the risk of developing Alzheimer's disease.(10) In another study, researchers found there was a correlation between vitamin B12 deficiency, hallucinations and diurnal rhythm disturbances in dementia patients.(11)

Vitamin B₁₂ deficiency has also been associated with depression in the elderly, and it may treat certain symptoms of Crohn's disease.(12, 13) Vitamin B₁₂ has been used experimentally to suppress the AIDS virus and to support health in AIDS patients, who are commonly deficient.(14) Vitamin B₁₂ may ease symptoms for people with bronchial asthma while possibly supporting healthy brain function in diabetics.(15, 16) Vitamin B₁₂ may also enhance sperm count and sperm activity in cases of male infertility.(17) Also of note is the fact that vitamin B₁₂ can prevent allergic reaction to sulfite.(18)

One study found that older women with lower levels of serum vitamin B12 had a greater risk of bone loss.(19)

The vitamin B₁₂ deficiency condition known as pernicious anemia can be effectively treated by supplementation with vitamin B₁₂ under the supervision of a health care professional.(20)