A new US study suggests women could cut their risk of heart attack by as much as one-third by eating three or more servings of blueberries and strawberries per week, the likely reason being because these foods are high in a class of dietary flavonoids known as anthocyanins.

The researchers write about their findings in the 15 January online issue of the American Heart Association journal Circulation.

They focused on blueberries and strawberries because they are the most-eaten berries in the US.

They suggest the same findings may be true of other plant foods high in anthocyanins, such as grapes, blackberries and eggplant. Anthocyanin is a pigment that is responsible for the red, purple, and blue colors of many plants.

For the study, researchers from the Harvard School of Public Health in the US and the University of East Anglia (UEA) in the UK, used data that had been collected as part of the US-based Nurses’ Health Study II.

The data-set they used came from 93,600 women aged 25 to 42 who were followed for 18 years starting in 1989, and during which time they had filled in questionnaires about their diet every four years.

During the study period, there were 405 heart attacks among the participants.

When they analyzed the results from the questionnaires against the rate of heart attack, the researchers found the women who ate the most blueberries and strawberries had a 32% lower rate in the risk of having a heart attack than the women who ate these berries once a month or less.

The figures stayed the same even after taking into account other potential influencing factors like age, high blood pressure, family history of heart attack, exercise, smoking, body mass, caffeine and alcohol intake.

Even women who had a diet rich in other fruits and vegetables did not show this level of reduced risk.

Lead author Aedín Cassidy, head of the Department of Nutrition at Norwich Medical School within the UEA, says in a statement:

“We have shown that even at an early age, eating more of these fruits [strawberries and blueberries] may reduce risk of a heart attack later in life.”

Senior author Eric Rimm, Associate Professor of Nutrition and Epidemiology at the Harvard School of Public Health, says women could easily incorporate blueberries and strawberries to their weekly food intake:

“This simple dietary change could have a significant impact on prevention efforts,” he urges.

Cassidy, Rimm, and colleagues suggest anthocyanins may help dilate arteries, prevent the build-up of plaque that causes arteries to narrow, and provide other cardiovascular benefits.

They also found that intake of foods rich in other other flavonoid subclasses were not significantly linked with risk of heart attack.

The study adds to a body of evidence about flavonoids and cardiovascular health, and appears to confirm that different subclasses of flavonoid have different effects.

Not long ago Cassidy also led another study, reported in the February 2012 online issue of another AHA journal, Stroke, that found a strong link between high consumption of flavonones in citrus fruits, especially oranges and grapefruit, and reduced risk of clot-associated or ischemic stroke in women.

In that study they looked at six major subclasses of flavonoids: flavonones, anthocyanins, flavon-3-ols, flavonoid polymers, flavonols and flavones, but found the link with reduced stroke risk was only strong for flavonone-rich foods.

Written by Catharine Paddock PhD