Cardiovascular diseases are among the leading causes of death worldwide. Numerous studies suggest that a plant-based diet rich in polyphenols—phytochemicals found in fruits, vegetables, tea, coffee, cocoa, nuts, and olive oil—can make an important contribution to heart health. Until now, however, it was unclear how overall dietary patterns and the actual intake of these plant compounds affect cardiovascular risk in the long term.
In this large-scale, long-term study, more than 3,100 adults from the British TwinsUK cohort were followed for an average of more than eleven years. In addition, polyphenol metabolites were measured in the urine of a subgroup to objectively assess actual intake.
The results show that people with a polyphenol-rich diet had a significantly lower risk of cardiovascular disease. The associations were particularly strong for flavonoids and phenolic acids—plant compounds found in berries, apples, citrus fruits, tea, coffee, and cocoa, among other foods. At the same time, lower blood pressure levels and higher HDL cholesterol levels were observed. The analyses of the urine samples largely confirmed these associations, thereby supporting the validity of the dietary data.
Conclusion: The study provides compelling evidence that a long-term diet rich in polyphenols is associated with better cardiovascular health. The authors view flavonoids and phenolic acids in particular as important components of a heart-healthy diet. At the same time, they emphasize that further intervention studies are needed to confirm the observed associations causally.
Background
Polyphenols are a large group of secondary plant compounds that occur naturally in plant-based foods. Tea, coffee, fruits, vegetables, berries, cocoa, nuts, olive oil, and some whole-grain products are particularly rich in polyphenols. Numerous experimental and clinical studies have shown that polyphenols possess antioxidant, anti-inflammatory, and vasoprotective properties, among others. In addition, they can improve endothelial function, inhibit the oxidation of LDL cholesterol, and support blood pressure regulation.
However, measuring actual polyphenol intake is difficult because their content in foods can vary considerably, and conventional dietary questionnaires provide only a limited picture of this intake. For this reason, the authors developed a specialized Polyphenol-Rich Dietary Score (PPS-D) that assesses the regular consumption of 20 food groups particularly rich in polyphenols. In addition, a metabolic polyphenol score (PPS-M) was calculated based on characteristic polyphenol metabolites in urine to objectively verify the dietary data.
Methods
The study is based on data from 3,110 participants in the British TwinsUK cohort, who were followed for an average of 11.2 years. Dietary habits were assessed using a validated dietary questionnaire, and the polyphenol dietary score was calculated from this data. At the same time, established markers of cardiovascular risk were measured, including systolic and diastolic blood pressure, total cholesterol, HDL cholesterol, and two internationally recognized cardiovascular risk scores (ASCVD Risk Score and HeartScore).
In addition, the researchers analyzed a total of 114 polyphenol metabolites in the urine of a subgroup of 200 individuals using modern mass spectrometry. This allowed them to objectively verify the dietary data collected via questionnaires and compare it with cardiovascular risk markers.
Results
The analysis revealed a consistent association between higher intake of polyphenol-rich foods and lower long-term cardiovascular risk. Participants with higher PPS-D scores had lower values for both the ASCVD Risk Score and the European HeartScore. These associations persisted even after adjusting for key confounding factors such as age, body weight, energy intake, and dietary fiber intake.
The positive associations were particularly strong for flavonoids, phenolic acids, and tyrosine derivatives. These polyphenol groups were associated with more favorable blood pressure levels, higher HDL cholesterol concentrations, and lower cardiovascular risk scores. Analysis of the urine samples also largely confirmed these observations: Several characteristic metabolites of these polyphenol classes were associated with a lower cardiovascular risk.
It is interesting to note that the polyphenol dietary score developed showed stronger associations with cardiovascular risk than the analysis of individual foods or individual polyphenol classes. This suggests that it is not individual foods but overall dietary patterns that are decisive. The authors attribute this to synergistic effects of various plant-based foods.
In this British population, the main sources of polyphenol intake included tea and coffee, followed by fruit, cocoa, whole-grain products, nuts, and vegetables. At the same time, the authors point out that the main sources of polyphenols may vary depending on dietary habits in other countries.
Conclusion
The study provides strong epidemiological evidence that a long-term diet rich in polyphenols is associated with a lower risk of cardiovascular disease. Flavonoids and phenolic acids, in particular, appear to play a significant role in this regard. It is worth noting that the results are not based solely on dietary questionnaires but are additionally supported by objective biomarkers in urine, which significantly increases the study’s validity.
The authors view diets rich in polyphenols as a promising approach to promoting long-term cardiovascular health. At the same time, they point out that further controlled intervention studies are needed to confirm the observed associations causally and to derive specific dietary recommendations for various population groups.