It turns out that “eat your colors” is good advice, especially for preventing high blood pressure. Researchers from Harvard and the University of East Anglia collected dietary and health information every 4 years from more than 150,000 adults. None of the participants had high blood pressure at the outset, but during the 14 years that the study lasted, nearly 35,000 of them were diagnosed with hypertension. People who ate the most blueberries and strawberries, fruits rich in the red and purple pigments called anthocyanins, were less likely to develop a blood pressure problem.
Although the difference was statistically significant, it was small: there was only an 8 percent difference between those who ate the most and those who ate the least fruits full of these flavonoids. People 60 years old or younger got the greatest benefit from a colorful diet. In this age group, eating more than one serving of blueberries a week was associated with a 10 percent drop in the likelihood of high blood pressure.
This is the largest but not the first study to show that flavonoids can be beneficial for blood pressure. Cocoa flavonoids in dark chocolate have been studied in double-blind trials; hibiscus flower tea and pomegranates have been shown to act like the blood pressure medicines known as ACE inhibitors. Other foods rich in anthocyanins should also be investigated. These would include cranberries, elderberries, black currants, raspberries, and blackberries.
[American Journal of Clinical Nutrition, Feb, 2011]