vitamin B12

NIH Office of Dietary Supplements (ODS) ↗ · Jul 2, 2025 · Källans villkor

Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement and a prescription medication. Because vitamin B12 contains the mineral cobalt, compounds with vitamin B12 activity are collectively called cobalamins [1 ]. Methylcobalamin and 5-deoxyadenosylcobalamin are the metabolically active forms of vitamin B12. However, two others forms, hydroxycobalamin and cyanocobalamin, become biologically active after they are converted to methylcobalamin or 5-deoxyadenosylcobalamin [1-3 ].

NIH Office of Dietary Supplements (ODS) ↗ · Jul 2, 2025 · Källans villkor

Vitamin B12 is present in many dietary supplements, often as cyanocobalamin, but other forms may also be used.

NIH Office of Dietary Supplements (ODS) ↗ · Jul 2, 2025 · Källans villkor

RCTs have found that vitamin B12 (and folic acid) supplements lower homocysteine levels but not CVD risk. The authors of a Cochrane Review of the effects of homocysteine-lowering interventions on cardiovascular events based on 15 studies in 71,422 participants concluded that supplements of vitamin B12 alone or with other B vitamins do not prevent heart attacks or reduce death rates in people at risk of or with CVD [78 ]. More recently, an extended follow-up of the B-PROOF trial, (which compared 400 mcg folic acid and 500 mcg vitamin B-12 daily with placebo) in 1,298 participants found that after a median of 54 months, the intervention had no effect on CVD risk [79 ]. Overall, the available evidence suggests that supplementation with vitamin B12 alone or in combination with other B-vitamins does not reduce the risk of CVD or of CVD-related death.

NIH Office of Dietary Supplements (ODS) ↗ · Jul 2, 2025 · Källans villkor

Some evidence from observational studies and clinical trials suggests that higher intakes or blood concentrations of vitamin B12 may increase the risk of cancer. However, other evidence contradicts those findings, showing a link between lower intakes or concentrations of vitamin B12 and an increased cancer risk or no link at all. More research is needed to clarify the association between high or low intakes of vitamin B12 and the risk of cancer. The evidence for a relationship between vitamin B12 and cancer risk is mixed. Some evidence supports a link between increased cancer risk and higher intakes or blood concentrations of vitamin B12, some supports a link with lower intakes or concentrations, and some evidence indicates no link at all.