More evidence that folic acid reduces risk of ischaemic strokeBMJ 2004; 328 doi: http://dx.doi.org/10.1136/bmj.328.7434.247-c (Published 29 January 2004) Cite this as: BMJ 2004;328:247
Men who consume relatively large amounts of folic acid have a significantly reduced risk of developing ischaemic stroke, concludes a newly reported study.
The study's lead author, Dr Ka He of Northwestern University in Illinois, and colleagues investigated a total of 725 incident strokes—455 ischaemic, 125 haemorrhagic, and 145 unknown types of stroke—that were documented during 14 years of follow up between 1986 and 2000.
The participants were part of the health professional follow up study, which was established in 1986 when 51 529 male US health professionals aged 40-75 answered a detailed questionnaire on medical history, lifestyle, and diet. Participants were mailed questionnaires in every other year to update information on potential risk factors and identify new cases of diseases (Stroke 2004;35: 169-74).
End points were all incident fatal and non-fatal strokes occurring between the return of the 1986 questionnaire and the end of follow up on 31 January 2000. A physician, blinded to risk factor status, reviewed participants' medical records if they reported an incident stroke in any of the follow up questionnaires. Most cases were diagnosed with neuroimaging, and fatal cases were identified by next of kin, colleagues, postal authorities, or by a search of the National Death Index and confirmed by medical records.
After adjustment for major lifestyle and dietary factors, high intake of folate was associated with a significantly lower risk of ischaemic but not haemorrhagic stroke. The multivariate relative risk of ischaemic stroke was 0.71 (95% confidence interval 0.52 to 0.96; P for trend=0.05) for the 20% men with the highest intake compared with the 20% with the lowest intake. Intake of vitamin B-12 was also inversely associated with risk of ischaemic stroke.
Dr Ka He said that this was not the first report to show that folic acid can reduce the risk of stroke. All told, the results seem conclusive and consistent enough to suggest that men should change their behaviour to protect their health. “I believe we should recommend men to increase their intake of folate to reduce stroke risk,” he said.
Folic acid is a B vitamin that is naturally found in fruits and vegetables. Recently, the US government ruled that manufacturers should fortify grain products with folic acid, adding it to flour, rice, pasta, and cornmeal.
Research has shown that extra amounts of folic acid help reduce levels of homocysteine, and some studies have associated lower homocysteine levels with a decreased risk of stroke (New England Journal of Medicine 1995;332: 286-91). Increased levels of homocysteine are thought to weaken the walls of the arteries (Stroke 1994;25: 1924-30).