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Refined carbohydrates increase stroke risk

BOSTON, MASSACHUSETTS. Nutrition experts have found that a high intake of refined carbohydrates increases hemorrhagic stroke risk, particularly among overweight or obese women, and cereal fiber reduces the risk. The team from Harvard Medical School examined links between carbohydrate intake, glycemic index (the extent to which a food raises blood sugar), glycemic load (measure of carbohydrate quality and quantity) and stroke risk. High carbohydrate intake is known to affect fat and sugar metabolism and could therefore play a role in cardiovascular disease. Evidence from epidemiologic studies has suggested that a diet with a high glycemic index may increase the risk of heart disease and diabetes, especially in those with a higher BMI.

In 1980, 78,779 healthy US women completed a food questionnaire and were monitored for 18 years. During this time there were 1,020 strokes including 515 ischemic strokes (blockage of a blood vessel near the brain) and 279 hemorrhagic strokes (rupture of a blood vessel near the brain). Women in the top fifth of carbohydrate intake had 2.05 times the risk of hemorrhagic stroke than those in the lowest fifth. Ischemic stroke was not significantly linked to carbohydrates. Analysis showed that the link was strongest in women with a BMI of 25 or above. Dietary glycemic load was also linked to total stroke risk, but only in women with a BMI of 25 or above.

One possible mechanism for the increase in stroke risk is that a high carbohydrate intake may increase blood pressure - an important risk factor for stroke. It may also increase levels of C-reactive protein (a marker of inflammation), which may be linked to higher stroke risk. Intake of cereal fiber was analysed, and those in the highest fifth of intake showed a 34 per cent lower risk of total stroke and a 49 per cent lower risk of hemorrhagic stroke compared with those in the lowest fifth. The results support a benefit of cereal fiber in preventing stroke. The study also confirmed well-known risk factors for stroke including smoking, high blood pressure, diabetes, family history of myocardial infarction, and BMI.
Oh, K et al. Carbohydrate Intake, Glycemic Index, Glycemic Load, and Dietary Fiber in Relation to Risk of Stroke in Women. American Journal of Epidemiology, Vol. 161, January 2005, pp161-169

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