B‐complex vitamin therapy for preventing cardiovascular events

Cardiovascular disease is the number one cause of death worldwide. The most common causes of cardiovascular disease leading to both morbidity and mortality are ischaemic heart disease, stroke, and congestive heart failure. Many people with cardiovascular diseases may be asymptomatic, and may have a high risk for developing myocardial infarction, angina pectoris, stroke (ischaemic, haemorrhagic or both). 'Emergent or new risk factors' for cardiovascular disease have been recently added to the established risk factors (diabetes mellitus, high blood pressure, active smoker, adverse blood lipid profile). One of these risk factors is elevated circulating total homocysteine levels. Homocysteine is an amino acid, and its levels in blood are influenced by blood levels of B‐complex vitamins: cyanocobalamin (B12), folic acid (B9) and pyridoxine (B6). High plasma total homocysteine levels are associated with an increased risk of atherosclerotic diseases. Hence, it has been suggested that B vitamin supplementation might reduce the risk of myocardial infarction, stroke, and angina pectoris. Preventive strategies might include healthy people with low or high risk for developing cardiovascular disease (primary prevention) and people with an established cardiovascular disease (secondary prevention). In this updated review, we included 12 randomised clinical trials involving 47,429 participants living in countries with or without mandatory fortification. We found no evidence that homocysteine‐lowering interventions, in the form of supplements of vitamins B6, B9 or B12 given alone or in combination, at any dosage compared with placebo or standard care, prevent myocardial infarction, stroke, or reduce total mortality in participants at risk or with established cardiovascular disease. Homocysteine‐lowering interventions compared with placebo did not significantly affect serious adverse events (cancer).