As several epidemiological studies have demonstrated that higher protein intake may reduce the risk of stroke, this prospective, cohort study was designed to further explore this association.

In 1988, a screening survey was performed in Hisayama, Japan. Subjects were 2，587 residents, ages 40 to 79 years, with a comprehensive assessment including a dietary survey. The subjects were followed prospectively for 19 years, with health examinations performed every one to two years. A daily monitoring system was used to identify stroke events. At baseline, stroke risk factors were also determined, with measures taken of body mass index, physical activity, blood pressure, lipid profiles and renal function. The intake of animal and vegetable protein were compared with the risk of stroke.

Age and gender adjusted incidence of total stroke decreased significantly with higher amounts of total protein intake (P＝0.03). The adjusted incidence of intracerebral hemorrhage decreased significantly with increased protein (P＝0.008), with no such association for subarachnoid hemorrhage. Multi-variable adjusted analysis revealed that, for every 10 g per day increment increase in total protein intake, a 15% lower risk of stroke was realized. Elevated levels of vegetable protein intake were associated with a lower incidence of total stroke and ischemic stroke (P<0.05). Elevated levels of animal protein were associated with a lower incidence of intracerebral hemorrhage (P＝0.01).

This study found that higher protein intake is associated with a lower risk of total stroke, with vegetable protein associated with lower risk of an ischemic stroke and animal protein associated with a lower risk of intracerebral hemorrhage.