Finding Out How Flavonoids Protect the Heart

July 11 -- THURSDAY, July 10 (HealthDay News) -- For years, scientists have known that flavonoids, antioxidants found in foods as diverse as fruit, vegetables, herbs, grains and chocolate, are heart-healthy.

Now, researchers who looked at the effects of flavonoid-rich foods on cardiovascular disease risk factors such as high blood pressure have linked certain foods with specific benefits.

Health benefits associated with flavonoids have been reported for decades, but it's still difficult for experts to make specific recommendations about which flavonoids to eat for specific health effects because of a lack of data. Antioxidants slow or prevent the oxidative process caused by substances called free radicals, which can cause cell dysfunction and the onset of heart disease and other health problems.

In the new study, Dr. Lee Hooper, a lecturer at the University of East Anglia in Norwich, U.K., and colleagues sifted through the 133 studies to look at the links between different flavonoid subclasses and flavonoid-rich foods on different risk factors for cardiovascular disease, such as unhealthy cholesterol, high blood pressure and blood flow.

Among the findings:

• Eating chocolate or cocoa increased a measure called flow-mediated dilation, which is a good indication of blood flow in the veins. It also reduced blood pressure, both systolic (the upper number, reflecting the maximum pressure exerted when the heart contracts) by about 6 points, and diastolic (the bottom number, reflecting the maximum pressure when the heart is at rest), by about 3.3 points. But it didn't seem to have an effect on so-called "bad" LDL cholesterol.
• Soy protein reduced diastolic blood pressure by almost 2 points of mercury and improved bad cholesterol but didn't improve so-called good HDL cholesterol. But those effects were found just for isolated soy protein, not for other soy products.
• A habit of green tea drinking reduced bad cholesterol levels, but drinking black tea boosted both systolic and diastolic pressure -- by 5.6 points for systolic and 2.5 for diastolic.