A new collaborative study between researchers at Harvard University and the University of East Anglia in the U.K. has found that a diet full of flavonoid-rich foods is linked to a reduced risk of erectile dysfunction, a condition that affects up to half of all middle-aged and older men.

Exercise is already known to be beneficial for those suffering from erectile dysfunction, however this is a pioneering study in terms of looking at how the condition can be improved by eating a diet rich in flavonoids, the compounds found in many plant-based food and drinks -- including fruit and vegetables, tea, herbs, and even wine -- that are known to have an antioxidant effect on the body.

To conduct their research, the two teams looked at more than 50,000 middle-aged men and questioned them at four-year intervals on their ability to have and maintain an erection that enabled them to take part in sexual intercourse. The men were questioned in 2000, 2004, and again in 2008. They were also asked to provide a history of their erectile dysfunction that dated back to 1986.

Information on their diet was also collected every four years, with the team focusing on the effects of six commonly consumed different types of flavonoids.

More than one third of the men reported that they suffered from erectile dysfunction, however the results showed that those consuming a diet rich in flavonoids were less likely to suffer from the condition, with just a few portions a week of flavonoid-rich foods decreasing the likelihood of suffering from erectile dysfunction by 10 per cent, with the strongest benefits seen in men under the age of 70.

A diet high in fruit was also linked to a 14 per cent educed risk, and when combining a flavonoid-rich diet with exercise, the risk was reduced even further, by 21 per cent. The research also showed that eating a flavonoid-rich diet is as beneficial for those suffering from erectile dysfunction as briskly walking for up to five hours a week.

Of the six flavonoids studied, the team found three in particular to be the most beneficial: anthocyanins, found in blueberries, cherries, blackberries, radishes and black currants; and flavanones and flavones, which are found in citrus fruits. The most popular sources of these three flavonoids in the US are strawberries, blueberries, red wine, apples, pears, and citrus products.

According to Dr Eric Rimm, senior author on the study, a diet rich in flavonoids could also have additional benefits, "As well as improving sexual health for middle-aged men, there is another important benefit linked to heart health. Erectile dysfunction is often an early barometer of poor vascular function and offers a critical opportunity to intervene and prevent cardiovascular disease, heart attack and even death.

"Men with erectile dysfunction are likely to be highly motivated to make healthier lifestyle choices, such as exercising more and eating the right foods -- which would greatly benefit their long-term cardiovascular health as well."

The research was published this week in The American Journal of Clinical Nutrition.