Scientists found three or more handfuls of strawberries or blueberries each week reduced the risk of heart attack in women by up to one-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.
"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.