Folate may protect against stroke independently of homocysteine levels

The B vitamin, found in green leafy vegetables and some bakery products, has previously been linked to lower risk of stroke, usually thought to be a result of its impact on homocysteine levels.

Homocysteine, an amino acid, has been associated with higher risk of stroke and Alzheimer's disease.

But the new study showed that folate may actually work independently of homocysteine levels to protect against one type of stroke - haemorrhagic strokes, or those caused by bleeding in the brain.

Writing in this month's issue of Stroke​ (vol 36, issue 7, pp1426-31), Dr Bethany Van Guelpen and colleagues from Umea University in Sweden said they examined blood and dietary levels of folate and vitamin B12 in 62 patients who had a haemorrhagic stroke and 334 who had an ischaemic stroke.

Blood levels of folate were inversely associated with the risk of hemorrhagic stroke, even after accounting for homocysteine levels and other risk factors like high blood pressure.

They found no association between blood levels of vitamin B12 and either type of stroke.

Nor was dietary folate associated with the risk of ischaemic stroke, although it was inversely associated with the risk of haemorrhagic stroke.

Van Guelpen's team notes that the lack of any association with ischemic stroke was unexpected.

They point out that the food in Sweden is not fortified with folate and intake of fruit and vegetables is relatively low, so folate levels might not have been high enough to show a protective effect against ischemic stroke.