New evidence shows that there is no correlation between stroke risk and dietary fats. Previously there was strong evidence that saturated fat and trans unsaturated fat increase the risk of coronary heart disease while monounsaturated and polyunsaturated fats decrease it. There is also some evidence that a high intake of long chain omega-3 fatty acids from seafood is associated with a lower risk of ischemic stroke (stroke caused by a blood clot), but not with the risk of hemorrhagic stroke (stroke caused by a burst blood vessel). Researchers at the Harvard School of Public Health now report that they have found no association between fat intake and stroke risk. Their study involved 43,732 male health professionals who were enrolled in 1986 and followed for 14 years. The men completed food frequency questionnaires in 1986, 1990 and 1994. They were between the ages of 40 and 75 years and free of diabetes and cardiovascular disease in 1986. By January 2000 455 ischemic strokes, 125 hemorrhagic strokes, and 145 strokes of unknown type had occurred in the group. The researchers found no statistically significant correlation between stroke risk and the intake of total fat, animal fat, vegetable fat, saturated fat, monounsaturated fat, polyunsaturated fat, trans unsaturated fat or cholesterol. They also found no correlation between stroke risk and consumption of red meats, high-fat dairy products, nuts and eggs.
He, Ka, et al. Dietary fat intake and risk of stroke in male US healthcare professionals: 14 year prospective cohort study. British Medical Journal, Vol. 327, October 4, 2003, pp. 777-82
Editor's comment: A total of 725 strokes among 43,732 men followed for 14 years gives a total incidence of 0.1% per year. This is considerably lower than the usually-quoted figure of about 1% for the US population in general. The lead author of the study, Dr. Ka He, MD, ScD, kindly provided the following explanation for the seeming anomaly (personal communication to me, November 30, 2003): The annual incidence of new and recurrent stroke in the US is about 700,000 according to the American Stroke Association. Based on a population of 270,000,000 the annual rate is 0.26 per 100 person-years or 0.26% per year. Stroke risk, of course, increases with age so it would clearly be higher if, for example, only people over 50 years of age were considered. Says Dr. He, "In our study, we only count the first event not recurrent stroke. Also, the participants are all healthcare professionals. They are health-conscious and relatively healthy (they were free from any CVD and diabetes). I would not be surprised if there is relatively low rate of stroke in our cohort".