Claim

Flavanoids from strawberries and blueberries cut heart attack risk in women by one third.

Verdict

False

The scientific literature simply does not support the claim that anthocyanin containing berries such as strawberries and blueberries reduce the risk of heart attacks in women.

Origin

Medical News Today reviewed the health benefits and nutritional breakdown of strawberries and claimed that strawberries can reduce the risk of heart attack in women by 32%. The article recommended taking three servings of strawberries per week and even provided a list of tips to make it easy to eat this super food on a daily basis.

The study referenced in this news feature was a piece of research published in the journal Circulation in 2013. Researchers from Harvard USA and Norwich Medical School UK studied the effect of dietary anthocyanin and flavanoid intake on heart disease in young and middle aged women.

The study participants were part of the well characterized Nurses Health Study. Data from 93,600 healthy women aged between 25 and 42 years of age were evaluated. The women were followed up for a total of 18 years using questionnaires which were sent regular mail.

(This study started in 1989 before the widespread use of the internet.)

Study participants filled out details relating to lifestyle, diet and any new cardiovascular events. During the 18 years of follow up, 405 women had a myocardial infarction. The average age of women who had a myocardial infarction in this study was 48.9 years.

Women who had a myocardial infarct had a lower intake of anthocyanin as compared to women who maintained good cardiovascular health over the 18 years of follow up. Eating more than three serving per week of both blueberries and/or strawberries resulted in a 32% decrease in the risk of myocardial infarction.

However, this reduction was not statistically significant, and was interpreted by the study authors themselves as just a ‘trend’.

Apart from the fact that the study results did not reach the level of statistical significance there are other problems with the over-interpretation of results of this study.

Firstly, this study only shows an association between colored berry intake and cardioprotective effects. It does not show that anthocyanin containing berries are directly responsible for the ‘trend’. As the authors of the study say ‘In a population based study like ours, it is impossible to distinguish the influence of fruits and vegetables.’ The  authors recommend that long term randomized control trials including different doses of red/blue coloured berries plus measurements of biomarkers of heart disease are needed to fully answer this question.

Secondly, the study focused on young / middle aged women. It is thought that the mechanism of heart disease in older women is entirely different to that in the younger/middle aged woman. This means that we cannot extrapolate the results of the study to ‘women’ in general.

In summary, it is too early to say if habitual consumption of red/blue colored berries can reduce the risk of heart disease in ‘women’.