It is well known that a poor diet is a major risk factor for stroke. Foods high in fat can lead to a build up of fatty plaques in the arteries that can cause atherosclerosis, while overweight and obesity can lead to high blood pressure and diabetes.
But according to the researchers of this latest study, including Dr. Xinfeng Liu of Nanjing University School of Medicine in China, past research has indicated that dietary protein may reduce stroke risk by lowering blood pressure.
However, the team notes that many of these studies remain inconclusive.
With this in mind, they set out to evaluate the link between dietary protein intake and stroke risk by conducting a meta-analysis of all available research in the field.
The analysis included seven studies involving a total of 254,489 participants. All subjects were followed for an average of 14 years.
The researchers found that at the end of the study period, participants who had the highest levels of protein in their diets were 20% less likely to experience a stroke, compared with subjects who had the lowest levels of protein in their diets.
In addition, the team found that for every additional 20 g of protein consumed each day, stroke risk decreased by 26%.
These findings remained even after taking other factors into account that may influence the risk of stroke, such as smoking and high cholesterol.
The study authors say their findings may have important implications for the worldwide population:
"According to the result of our meta-analysis, a 20 g/d increment in protein intake was associated with a reduction in the risk of stroke of 26%. This risk reduction would be translated into a reduction of 1,482,000 stroke deaths every year worldwide and is expected to produce overall health benefits by decreasing the level of disability."
Although the team cannot pinpoint the exact reasons as to why dietary protein appears to reduce stroke risk, they believe that in part, it could be attributable to a blood pressure-lowering effect of protein.
They add that in one study, higher protein levels significantly reduced triglyrcerides, total cholesterol and non-high-density lipoprotein cholesterol (bad cholesterol), compared with participants who followed a high-carbohydrate diet, which could explain the reduced risk of stroke.
Furthermore, they note that dietary protein could reduce stroke risk through a "substitution effect" - the protein may replace the intake of other potentially harmful foods.
The reduced risk of stroke was stronger for participants who consumed a lot of animal protein rather than vegetable protein.
However, the team notes that their findings suggest that dietary protein should be gained from fish rather that red meat, which has been associated with a higher risk of stroke. They say this is evident as two of the seven studies they analyzed were conducted in Japan, where fish intake is higher and red meat intake is lower.
However, the investigators note that their study is subject to some limitations. For example, the number of participants who consumed vegetable protein was small, therefore this may have influenced the greater stroke-reducing effects seen with animal protein.
Fast facts about stroke
In addition, the team says that dietary protein intake tends to be linked with other nutrients that may prevent stroke, such as dietary fiber, magnesium and potassium.
"However, the association between protein intake and risk of stroke persisted when we confined the analysis to studies that adjusted for these risk factors," they add.
They conclude that further research is warranted to confirm whether a diet higher in protein can reduce the risk of stroke.
In an editorial linked to the study, Dr. Arturo Tamayo, of the University of Manitoba in Canada, and Dr. Luis Castilla-Guerra, of the Hospital de la Merced in Spain, say that the study results "should be viewed cautiously," particularly when it comes to the finding that animal protein is more beneficial than vegetable protein.
However, they note the importance of determining what diets are most effective for reducing stroke risk and say the study "opens new avenues of research in stroke prevention with prospective, well-controlled clinical trials comparing major cardiovascular diets."
It is not only stroke risk that may be influenced by a diet higher in protein. Medical News Today recently reported on a study published in the Journal of the American Geriatrics Society, which suggested that a diet high in animal protein may prevent functional decline in older men.
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