A diet rich in polyphenols—natural compounds found in foods such as berries, coffee, olive oil, cocoa and nuts—may significantly improve long-term heart health, according to a new international study. The findings add to growing evidence that what people eat plays a crucial role in preventing cardiovascular disease, the world’s leading cause of death.

Cardiovascular health is influenced by several lifestyle factors, including regular physical activity, avoiding smoking and managing stress. However, diet remains one of the most powerful and modifiable risk factors. Previous research has already shown that nutrients such as fiber, omega-3 fatty acids, antioxidants, potassium and magnesium support heart health. The latest study highlights polyphenols as another key dietary component with potential cardiovascular benefits.

The research, published in BMC Medicine, was led by scientists from King’s College London and focused on data from more than 3,100 adults enrolled in the long-running TwinsUK cohort. Participants were followed for over a decade, during which their dietary habits and heart disease risk were closely monitored.

To assess polyphenol intake more accurately, researchers went beyond food questionnaires. A subset of 200 participants provided urine samples, allowing scientists to measure polyphenol metabolites—breakdown products that reflect how much of these compounds the body actually absorbs. These measurements were then compared with standard cardiovascular risk scores, including the Atherosclerotic Cardiovascular Disease (ASCVD) risk score and HeartScore.

The results showed that participants with higher levels of polyphenol metabolites had lower predicted cardiovascular risk and higher levels of HDL, or “good,” cholesterol. “People who had more polyphenol breakdown products in their urine tended to show a more favourable cardiovascular profile,” said Dr Ana Rodriguez-Mateos, senior author of the study and professor of human nutrition at King’s College London.

While the study was observational and does not prove cause and effect, researchers noted a consistent pattern: individuals who consumed more polyphenol-rich foods maintained better heart health over time. Importantly, the study also found that although cardiovascular risk increases naturally with age, this rise was slower among those with higher polyphenol intake.

“Evidence from many controlled trials suggests that polyphenols help blood vessels function better, lower blood pressure and improve blood lipid profiles,” Dr Rodriguez-Mateos explained. These compounds are believed to work through multiple mechanisms, including improving nitric oxide availability in blood vessels, which supports healthy circulation.

Independent experts say the findings strengthen existing knowledge about the protective role of plant-based compounds. Dr Cheng-Han Chen, an interventional cardiologist in the United States, noted that polyphenols are known for their antioxidant and anti-inflammatory properties, which can help reduce key risk factors such as high blood pressure, cholesterol, diabetes and obesity.

Nutritionists emphasize that incorporating polyphenols into daily meals does not require drastic dietary changes. Common foods such as fruits, vegetables, whole grains, beans, nuts, tea, herbs, spices and even dark chocolate are rich sources. “You don’t have to overhaul your entire diet,” said registered dietitian Monique Richard. “Small, consistent shifts toward more plant-based foods can support heart, gut and brain health.”

Researchers are now planning randomized controlled trials to determine whether increasing polyphenol intake directly improves heart health markers. They are also developing advanced biomarker tools to better understand how diet influences long-term cardiovascular outcomes.

As evidence continues to mount, experts agree on one clear message: diets rich in plant-based, minimally processed foods—such as the Mediterranean, DASH and Alternative Healthy Eating Index diets—remain among the most effective strategies for protecting the heart and reducing the global burden of cardiovascular disease