Eating 5 fruits and vegetables a day may not be enough for heart health, study finds

When it comes to eating fruits and vegetables for heart health, the choice of fruits and vegetables may be just as important as how many they eat, new research suggests.

Health experts have long recommended the "five a day" guideline, meaning people should eat five servings total of fruits and vegetables.

A group of scientists, however, contends in a new study that adhering to dietary guidelines may not provide enough flavanols — plant compounds linked to cardiovascular benefits.

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Flavanols are a type of antioxidant found in plants that has been shown to help improve blood flow and reduce inflammation and has been associated with a lower risk of death from heart disease.

The researchers cited previous studies that associated a daily intake of 500 milligrams of flavanols with cardiovascular benefits.

"Evidence from the COSMOS trial, the largest randomized controlled study on polyphenols to date, demonstrated that an intake of 500 milligrams [a] day of flavanols significantly reduced cardiovascular disease mortality by 27%," they wrote.

"Because fruits and vegetables, including legumes, are major sources of flavanols, and fruits and vegetables are emphasized in current dietary guidelines in the U.S., [the U.K.] and by the World Health Organization, it is plausible that adherence to these dietary guidelines could already deliver sufficient flavanol intake levels."

No data currently demonstrates whether the recommended fruit and vegetable intake levels and broader healthy dietary patterns provide flavanol levels associated with cardiovascular benefits, the researchers added.

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The scientists analyzed the diets and biomarker data of more than 30,000 adults in the U.S. and U.K. 

They found that even among people who met the dietary guidelines for fruits and vegetables, fewer than 25% achieved an estimated flavanol intake of 500 milligrams or more per day, the level associated with cardiovascular benefits in previous studies.

The group of researchers — from the University of Reading, Harvard Medical School, the University of California, Davis and Mars, Inc. — concluded that following current dietary guidelines alone may not provide enough flavanols to reach intake levels associated with cardiovascular benefits noted in previous studies. 

The study examined estimated flavanol consumption and did not directly measure cardiovascular outcome. "Specific dietary reference values for flavanols may still be necessary if aiming to increase the intake of these dietary compounds," they wrote in the study, published by the journal Food & Function.

Researchers said the findings suggest that people looking to increase flavanol intake may need to pay closer attention to the specific fruits, vegetables and other plant-based foods they consume.

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"Including blueberries, plums, blackberries, broad beans or cherries (washed down with green tea) in your five-a-day may be the best way to a healthier heart," the University of Reading said in a release.

"Flavanols can significantly reduce the risk of dying from cardiovascular disease, but only if you consume enough of them," said Javier Ottaviani, the study's lead author.

"Most people assume that eating plenty of fruit and vegetables covers this, but what this research shows is that the specific choices you make matter far more than the total amount. Including a handful of blackberries, a whole apple or having a cup of green tea alongside your meal could make a real difference to how much of these beneficial compounds you consume and absorb from the diet."

The top fruits and vegetables with the highest flavanol content per portion, according to the study, are these: plums, cranberries, blackberries, green tea, broad beans, cherries, apples with skin, strawberries, blueberries and pinto beans.

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"Five-a-day is the right message, but we may need to think more carefully about which five," said University of Reading professor Gunter Kuhnle.

"Different fruits and vegetables offer very different nutritional benefits beyond vitamins and minerals, and as our understanding of these compounds grows, there is a real opportunity to make dietary guidance more specific and more effective."

"This research is a step toward understanding what that might look like in practice."