Strawberries may be synonymous with summer, but eaten all year round they can prevent heart attacks, a study suggests.
Scientists found that three or more handfuls of strawberries or blueberries each week reduced the risk of heart attack in women by up to a third.
Both fruits contain specific kinds of flavonoid plant compounds that appear to combat blocked arteries, say the researchers.
The study involved 93,600 participants in the Nurses' Health Study II, a major US investigation of women's health.
Women aged 25 to 42 completed questionnaires about their diet while their health was monitored over 18 years.
During the study, 405 heart attacks were recorded. Women who ate the most strawberries and blueberries were 32% less at risk than those who consumed the berries no more than once a month.
Even participants with diets rich in other fruits and vegetables were more likely to experience heart attacks if they avoided strawberries and blueberries.
Dr Eric Rimm, one of the senior study authors from the Harvard School of Public Health in Boston, said: "Blueberries and strawberries can easily be incorporated into what women eat every week.
"This simple dietary change could have a significant impact on prevention efforts."
The findings appear in the American Heart Association journal Circulation.
Scientist believe the protective effect could be linked to anthocyanins, a type of flavonoid that may help open up arteries and counter the build-up of fatty deposits on blood vessel walls.
"We have shown that even at an early age, eating more of these fruits may reduce risk of a heart attack in later life," said nutritionist Dr Aedin Cassidy, from the University of East Anglia, who took part in the research.
The scientists took account of risk factors such as age, high blood pressure, body mass, lack of exercise, smoking, caffeine and alcohol consumption, and family medical history, that could have influenced the results.
Other foods may have similar benefits, say the researchers. Strawberries and blueberries were chosen for the study because they are the most commonly eaten berries in the US.
Victoria Taylor, senior dietitian at the British Heart Foundation, said: "This study found an association between a diet rich in red and purple fruits, such as blueberries, blackberries and strawberries, and a reduction in heart attack risk for young and middle-aged women.
"However, more research is needed to understand why this link between berries and better heart health exists. We would need to know more before we make specific recommendations about individual fruit and vegetables in relation to heart disease.
"But in the meantime, this is yet another good reason to make sure we get our five a day and enjoy the wide variety of fruit and vegetables available to us."
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