"The amount of protein that led to the reduced risk was moderate-equal to 20 grams per day," said study author Xinfeng Liu, MD, PhD, of Nanjing University School of Medicine in Nanjing, China. "Additional, larger studies are needed before definitive recommendations can be made, but the evidence is compelling."
The meta-analysis looked at all of the available research on the relationship between protein in the diet and the risk of stroke. Seven studies with a total of 254,489 participants who were followed for an average of 14 years were included in the analysis.
Overall, the participants with the highest amount of protein in their diets were 20 percent less likely to develop a stroke than those with the lowest amount of protein in their diets. The results accounted for other factors that could affect the risk of stroke, such as smoking and high cholesterol. For every additional 20 grams per day of protein that people ate, their risk of stroke decreased by 26 percent.
"If everyone's protein intake were at this level, that would translate to more than 1.4 million fewer deaths from stroke each year worldwide, plus a decreased level of disability from stroke," said Liu.
Liu noted that the analysis does not support increased consumption of red meat, which has been associated with increased stroke risk. Two of the studies were conducted in Japan, where people eat less red meat than westerners do and more fish, which has been associated with decreased risk of stroke.
"These results indicate that stroke risk may be reduced by replacing red meat with other protein sources, such as fish," Liu said.
The reduced risk of stroke was stronger for animal protein than vegetable protein.
Protein has the effect of lowering blood pressure, which may play a role in reducing stroke risk, Liu said.
The study was supported by the National Natural Science Foundation of China and the Natural Science Foundation of Jinling Hospital in Nanjing, China.
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The American Academy of Neurology, an association of more than 27,000 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer's disease, stroke, migraine, multiple sclerosis, brain injury, Parkinson's disease and epilepsy.