Most people know that a diet high in saturated fat can increase blood cholesterol and thus increase risk of heart disease. What they don't know is that so-called "banned foods," foods high in fat or cholesterol, including red meat, high fat dairy products, nuts, and eggs have wrongly been indicted as culprits in increased risk for stroke. While a diet high in saturated and trans-unsaturated fatty acids has been shown to be a predictor for heart disease, scientific support is lacking for extrapolating this finding to stroke. New findings from a major study released in the Oct. 4 issue of the British Medical Journal help discriminate between heart disease and stroke.
Researchers from the Harvard School of Public Health followed 43,732 healthy middle-aged U.S. male health professionals for fourteen years to examine the association between total fat intake, specific types of fat and cholesterol, and the risk for stroke. Of the 725 new strokes documented during the follow-up period, 455 were ischemic strokes (those caused by fatty blockage in the arteries to the brain), 125 were hemorrhagic strokes (those caused by bleeding within the brain), and 145 were strokes of unknown type. After controlling for potential confounders, investigators found no evidence that intake of total fat, cholesterol, or specific types of fat affects the risk of developing stroke.
Previous studies have indicated that saturated or trans-unsaturated fat intake may actually reduce stroke risk. Results of the Framingham study indicated that saturated fats were associated with a protective effect on stroke. Another study conducted by the Department of Ambulatory Care and Prevention at Harvard documented similar findings, suggesting an association of fat intake, both saturated and monounsaturated (from olive oil or canola oil, for example), with reduced stroke incidence.
What should you make of these findings? Researchers urge caution when interpreting the results of this latest study. While the study certainly does join others in casting serious doubt on claims suggesting an association between high fat intake and increased incidence of stroke, it does not alter the basic public health message. Diet remains important, not, it seems, for stroke prevention but rather to protect against coronary heart disease.
Known risk factors for stroke, the third leading cause of death in the U.S., include high blood pressure, chronic excessive alcohol consumption, lack of exercise, smoking, and untreated diabetes. For effective stroke prevention, you should have your blood pressure screened annually, moderate your alcohol consumption, exercise regularly, kick the butts (see ACSH's book on Kicking Butts), and adhere to diabetic treatment guidelines set forth by your physician. But to date, the accumulated evidence does not support an association between a high fat diet and increased risk for stroke.