Lack of association between dietary protein intake and risk of stroke among middle-aged men

Prospective cohort studies in Japanese populations have shown an inverse association between dietary protein and stroke risk. However, this association has not been examined among any study populations of US men.

Our objective was to examine the relation between dietary protein and risk of stroke in men who participated in the Health Professionals Follow-Up Study.

A total of 43,960 men who were free of cardiovascular disease and cancer at baseline were included in the analysis. Dietary protein (total, animal, and vegetable) was assessed with the use of a food-frequency questionnaire at 5 time points during the follow-up period of 1986-2004. Cox proportional hazards models were used to calculate multivariate relative risks and 95% CIs, which represented the effect of the substitution of protein for an equal percentage of energy from carbohydrate.

During 18 y of follow-up there were 1057 incident stroke events (638 ischemic, 171 hemorrhagic, and 248 of unknown type). For total stroke, the relative risk for the top quintile of percentage energy from protein compared with the bottom was 1.14 (95% CI: 0.90, 1.43; P for linear trend: 0.43) for total protein, 1.11 (95% CI: 0.87, 1.41; P for linear trend: 0.52) for animal protein, and 0.82 (95% CI: 0.60, 1.12; P for linear trend: 0.17) for vegetable protein. The results were similar when ischemic and hemorrhagic stroke subtypes were considered separately.

In contrast to studies in Japanese populations, this study did not show a statistically significant association between total, animal, or vegetable protein and risk of stroke in this population of US men.