MedicalResearch: What are the main findings of the study?
Dr. Lamuela-Raventós: We have found an inverse relationship between polyphenol intake and risk of overall mortality among elderly subjects at high cardiovascular risk. Adjusting for confounders and comparing the highest versus the lowest quintiles of intake, total polyphenols were inversely associated with total mortality (HR=0.63, 95 CI=0.41-0.97, P-trend=0.12), as well as stilbenes (HR=0.48, 95 CI=0.25-0.91, P-trend=0.04) and lignans (HR=0.60, 95 CI=0.37-0.97, P-trend=0.03). In fact, our results showed that all polyphenols subgroups, except for dihydrochalcones, trended to be protective although their intake did not reach statistical significance. In stratified analyses we also found a stronger association between total polyphenol intake and mortality risk for women and for those who did not drink alcohol.
Among flavonoid subclasses, we also found that isoflavones were strongly and lineally associated with the risk of mortality (HR=0.49, 95 CI=0.28-0.84, P-trend=0.009). However, the intake of isoflavones in our population was very low, the mean of the highest quintile was 0.05 mg/day, so we can only speculate about their protective effect.
MedicalResearch: Were any of the findings unexpected?
Dr. Lamuela-Raventós: Flavonoids are the main polyphenol subgroup, with intakes representing more than 50% of total polyphenols. Previous clinical and epidemiological studies had been focused only on the health effects of flavonoids or flavonoid subclasses such as anthocyanidins, flavonols, flavonols or isoflavones, but other subclasses had never or scarcely been studied. Therefore, we expected positive associations with flavonoids or other subclasses but they did not reach statistical significance. Although intake of minor subclasses such as lignans and stilbenes was lower compared with flavonoids and phenolic acids, the associations were unexpectedly significant.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Lamuela-Raventós: Fruits, vegetables, olives, virgin olive oil and beverages that derived from them (wine, beer, coffee…) are a good source of polyphenols. As far as we know, not all polyphenols have the same health effects because they have different structures and bioavailability. General recommendations already include fruits and vegetables to lower the risk of chronic diseases. In order to give detailed information to clinicians and patients, we need to translate our findings to real food. For example, lignans can be consumed through virgin olive oil, whole-grain wheat and seeds among others while wines, grapes and some berries are a great source of stilbenes.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Lamuela-Raventós: Although we have found promising associations we are not able to demonstrate a cause-effect relationship due to the nature of our study. Clinical studies should be done to clarify the benefits that derive from long-term consumption of polyphenols, particularly, stilbenes, lignans and isoflavones. Based on our results, we would also suggest studying the interaction of alcohol with polyphenol benefits.