A new study suggests that simply eating five fruits and vegetables a day may not be enough to deliver heart health benefits linked to certain plant compounds called flavanols.

Researchers from the University of Reading, Harvard Medical School, the University of California Davis, and Mars, Inc. found that many people who meet daily dietary guidelines still fall short of the flavanol levels associated with cardiovascular benefits in previous studies.

The new research focused on flavanols, a type of antioxidant that has been linked to improved blood flow, reduced inflammation, and a lower risk of heart disease-related death.

After analyzing diet and biomarker data from more than 30,000 adults in the United States and United Kingdom, scientists found that fewer than 25% of participants who met fruit and vegetable intake guidelines consumed 500 milligrams of flavanols per day.

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According to earlier clinical evidence from the COSMOS trial, an intake of 500 milligrams of flavanols daily was associated with a 27% reduction in cardiovascular disease mortality.

Because fruits and vegetables are stressed in official dietary advice from the U.S., the U.K., and the World Health Organization, researchers initially suggested that meeting those guidelines might deliver adequate flavanol levels.

However, their findings revealed that even strict adherence to recommended daily servings does not guarantee the intake levels associated with measurable cardiovascular benefits.

The study noted that certain fruits and vegetables contain much higher amounts of flavanols than others, meaning that food selection, not just quantity, plays a critical role.

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“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,” said study author Javier Ottaviani.

He added that including foods such as blackberries, apples, or green tea could meaningfully affect how much of these beneficial compounds a person consumes and absorbs.

The study identified plums, cranberries, blackberries, green tea, broad beans, cherries, apples with skin, strawberries, blueberries, and pinto beans as the top sources of flavanols per serving.

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

The study, published in the journal Food & Function, did not directly measure cardiovascular outcomes but analyzed estimated flavanol consumption.

Researchers concluded that “specific dietary reference values for flavanols may still be necessary if aiming to increase the intake of these dietary compounds.”

They emphasized that while fruits and vegetables generally support heart health, the difference in flavanol content across foods suggests that dietary guidance might benefit from being more detailed in the future.

Dr. Jeremy London, a heart surgeon in Georgia, said that knowing which foods offer optimal cardiovascular protection could help people make more informed choices.

The researchers pointed out that even simple additions, such as blueberries or green tea, could bring diets closer to the 500-milligram flavanol intake level seen to impact heart disease risk.

“Different fruits and vegetables offer very different nutritional benefits beyond vitamins and minerals,” said Kuhnle, adding that continued study could help refine dietary recommendations.

The findings, the authors said, mark a step toward making existing dietary guidelines more specific and effective for long-term heart health.