Use of B vitamins in stroke prevention
Potential benefits of B vitamin therapy to lower homocysteine concentrations in people at high risk of stroke warrant further investigation.
Stroke is an important cause of death and a leading cause of disability, but it is a preventable condition.
Lowering plasma homocysteine concentrations should help to prevent strokes. One way of doing this is by vitamin B therapy. Although early studies showed no overall benefit this may have been because they included people with kidney failure, who can be harmed by the adverse effects of cyanocobalamin, which is a form of vitamin B12.
Some of these studies showed that, while the number of strokes was reduced, there was an increase in myocardial infarctions.
High levels of homocysteine, an amino acid mainly related to meat eating, are associated with atherosclerosis, atrial fibrillation and blood clots. Folate therapy, a combination of nutrients including vitamins B6 and B12, lowers homocysteine levels but, as cyanocobalamin breaks down, cyanide is produced. This is not usually a problem as it is quickly cleared from the body, but it can build up in people with poor renal function.
The high burden of stroke is expected to increase because of the ageing population, the decline in renal function associated with ageing and the high prevalence of vitamin B12 deficiency in older people.
This article suggests that we should look again at vitamin B therapy to reduce homocysteine, but should conduct trials with methylcobalamin or hydroxocobalamin rather than the potentially toxic cyanocobalamin.
Spence J, Yi Q, Hankey G (2017) B vitamins in stroke prevention: time to reconsider. The Lancet. Neurology. 16, 9, 750-760.