Men who consume relatively large amounts of the B vitamin called folic acid (folate), are at significantly lower risk of the most common type of stroke, new research from Northwestern University in Illinois shows.
During a 14-year-long study, men with the highest intake of folic acid were almost 30 percent less likely to develop an ischemic stroke (caused by a blocked blood vessel) than men with the lowest folic acid intake.
This is not the first report to demonstrate that folic acid can reduce the risk of stroke. All told, the results appear conclusive and consistent enough to suggest that men change their behavior to protect their health, the lead researcher noted. He added that the recommended dietary allowance for folic acid in adults is 400 micrograms per day, which men can get from their diet or a supplement.
Folate is naturally found in lentils, beans, avocados, asparagus and leafy green vegetables, especially spinach. Recently, the US and Canadian governments mandated that manufacturers fortify grain products with folic acid, adding it to flour and pasta (and cornmeal in the US only). Multivitamins generally contain 400 micrograms of folic acid, the synthetic version of the B vitamin.
Previous research has shown that extra amounts of folic acid help reduce levels of an amino acid called homocysteine. Certain studies have suggested that reduced levels of homocysteine can decrease a person's risk of having a stroke. It has been shown that an excess of homocysteine, which the body makes when it absorbs and uses protein, can somehow damage the walls of the arteries.
Indeed, previous analyses of nutritional surveys of almost 10,000 adults conducted between 1971 and 1975 suggested that people who get enough folate in their diets seem to have a lower risk of stroke than those who eat fewer folate-rich foods.
In the current study, the researchers followed 43,732 men between the ages of 40 and 75 for 14 years, noting what they ate and whether they developed ischemic or hemorrhagic strokes. Folic acid intake had no effect on men's risk of hemorrhagic stroke. Folic acid may have had no effect on the risk of hemorrhagic stroke (a relatively rare type of stroke caused by bleeding in the brain) because the two types of stroke occur for very different reasons, and homocysteine plays a role primarily in ischemic stroke.
Men who consumed the most folic acid (half of them had intakes over 821 micrograms per day) had a significantly lower risk of ischemic stroke than men who consumed the least amount of folic acid (around 262 micrograms each day or less).
A high intake of vitamin B12 also appeared to reduce the risk of ischemic stroke, while there appeared to be no advantage to relatively large amounts of vitamin B6.
Although folic acid and vitamins B12 and B6 all theoretically influence homocysteine levels in the body, B6 may have failed to affect stroke risk because most men included in the study obtained enough of the vitamin, or because the vitamin interacts with homocysteine less strongly than the other B vitamins.
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