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Here's a new way for middle-aged men to ward off erectile dysfunction (ED): Eat more fruit, specifically foods rich in flavonoids, such as blueberries, strawberries, blackberries and citrus fruits.

That could help reduce the risk of ED by more than a fifth, according to findings published in The American Journal of Clinical Nutrition.

The researchers analyzed population-based data of more than 50,000 middle-aged men. Information was collected on the men's ability to get and maintain an erection firm enough for intercourse. Also, dietary data was collected every four years since 1986.

They found that men who consumed foods high in flavonoids -- particularly anthocyanins, flavones and flavanones -- had a lower risk of erectile dysfunction than men who did not consume such foods. Anthocyanins are present in blueberries, cherries, strawberries, blackberries, radishes and black currants, while flavones and flavanones are found in citrus fruits.

Previous research has shown that regular exercise may lower men's risk for erectile dysfunction. However, results of this study suggest that eating more flavonoid-rich foods is as beneficial for erectile dysfunction as walking briskly for up to five hours a week.

What’s more, men who combined a flavonoid-rich diet with regular exercise were found to have a 21 percent reduced risk of erectile dysfunction, compared with men with low flavonoid consumption and low physical activity.

It’s estimated that around 30 million men in the U.S. have erectile dysfunction. Men over the age of 60 are at greatest risk, though it occurs in around 12 percent of men under this age.