Dietary Protein Intake and Stroke Risk in a General Japanese Population: The Hisayama Study

Background and Purpose— The influence of dietary protein intake on stroke risk is an area of interest. We investigated the association between dietary protein intake and stroke risk in Japanese, considering sources of protein. Methods— A total of 2400 subjects aged 40 to 79 years were followed up for 19 years. Dietary protein intake was estimated using a 70-item semiquantitative food frequency questionnaire. The risk estimates for incident stroke and its subtypes were calculated using a Cox proportional hazards model. Results— During the follow-up, 254 participants experienced stroke events; of these, 172 had ischemic stroke, and 58 had intracerebral hemorrhage. Higher total protein intake was significantly associated with lower risks of stroke and intracerebral hemorrhage (both P for trend <0.05). With regard to sources of protein, the risks of total stroke and ischemic stroke significantly decreased by 40% (95% confidence interval, 12%–59%) and 40% (5%–62%), respectively, in subjects with the highest quartile of vegetable protein intake compared with those with the lowest one. In contrast, subjects with the highest quartile of animal protein intake had a 53% (4%–77%) lower risk of intracerebral hemorrhage. Vegetable protein intake was positively correlated with intakes of soybean products, vegetable, and algae, whereas animal protein intake was positively correlated with intakes of fish, meat, eggs, and milk/dairy products. Both types of protein intakes were negatively correlated with intakes of rice and alcohol. Conclusions— Our findings suggest that higher dietary protein intake is associated with a reduced risk of stroke in the general Japanese population.