Researchers investigate impact of flavonols on stroke risk

Jul 12 2010

New research has found that people who consume relatively high amounts of flavonols have a lower risk of stroke. Tea was most likely the major contributor of flavonols in the diet, ranging from 30 percent (US) to 70 percent (the Netherlands) of the total intake.

Flavonols are a subclass of flavonoids.  Flavonoids are dietary compounds found in tea, wine, cocoa, fruit and vegetables.  They contribute significantly to taste, color and possibly offer health benefits.  In this meta-analysis of six studies from the Netherlands, Finland and the US, the research team investigated the impact of flavonols on stroke risk, across a variety of populations. Research findings were published in the Journal of Nutrition.

There is evidence from prospective cohort studies that tea and flavonols are inversely related to stroke risk. This new meta-analysis found that a high intake of flavonols compared to low intake was associated with a 20 percent lower risk of stroke. The results suggest that higher flavonol intake may help maintain cardiovascular health. As flavonols are the only flavonoids that do not differ between the black and green tea varieties, they are an exciting and emerging area of interest for tea researchers. These new findings, together with results published last year by Dr. L. Arab, that found a 21 percent reduction in stroke risk associated with drinking more than three cups of tea daily, suggest that flavonols may be of particular importance for helping maintain heart health.

The researchers for this new meta-analysis analyzed data from studies that had a total of 111,067 participants with 2,155 fatal and non-fatal cases of stroke. Participants were followed for between six and 28 years and adjustments were made for age, gender, body mass index, smoking and blood pressure. Prevalent cases of cardiovascular disease were excluded in the analyses.

The authors acknowledge that the intake of flavonols has been positively associated with a healthy lifestyle and that this could have wider implications: it can be presumed that those people who have a healthy lifestyle are more likely to be non-smokers and have lower intakes of total saturated fat and lower BMI. The authors also remarked that the contribution of onions to the flavonol intake may have been underestimated in this research, because onions tend to be a hidden ingredient in soups and sauces.

Dr. Douglas Balentine, Director Nutrition Sciences, for Tea-based beverages at Unilever comments: "This research is groundbreaking as it is the first to investigate an association specifically between flavonol intake and the incidence of stroke. It adds to accumulating evidence that higher flavonoid intake is associated with helping maintain cardiovascular health. As tea is a major source of flavonoids in many diets, it is an exciting area of tea science as it may have a major public health impact."