Berry Compounds Show Support for Improved Blood Pressure
Lee Swanson Research Update
Increased intakes of anthocyanins—mainly from blueberries and strawberries—were associated with a reduction in the risk of high blood pressure (hypertension) of up to 12%, according to collaboration between scientists from the University of East Anglia (UK), Harvard School of Public Health and Harvard Medical School.
High blood pressure, defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg respectively, is a major risk factor for cardiovascular disease (CVD).
The results are derived from data from more than 150,000 health care professionals in the U.S. The study is observational in nature, and the researchers stress that this does not prove that the compounds do reduce the risk of hypertension; the data does not prove causation.
"These findings warrant further investigation, including intervention studies designed to test optimal doses of anthocyanin-rich foods for the prevention of hypertension and to underpin guidelines for the prevention and treatment of hypertension," the researchers wrote in the American Journal of Clinical Nutrition.
Led by Harvard’s Eric Rimm, the researchers analyzed data from 133,914 women and 23,043 men. Intakes of flavonoids and the various subclasses were calculated using food frequency questionnaires performed every four years. Subjects were followed for an average time span of 14 years, during which time a total of 5,629 and 29,018 cases of hypertension were documented in men and women, respectively.
The researchers found that the highest average intakes of anthocyanins (ranging from 16.2 to 21 mg/day) were associated with an eight percent decrease in the risk of hypertension (the benefits increased to a 12% reduction in risk when the analysis was limited to people over the age of 60) compared with the lowest average intakes, which ranged from 5.7 to 6.8.
No other subclasses of flavonoids were associated with hypertension, but the researchers did note that the compound apigenin was associated with a five percent reduction in risk, when comparing the highest with the lowest average intakes. Moreover, a six percent reduction in hypertension risk was observed for people over 60 with the highest average intakes of flavin-3-ol catechin, they added.
In terms of the whole foods, a significant 10% reduction in the risk of hypertension was observed in over 60-year-olds consuming more than one serving of blueberries per week, compared with people in the same age group consuming no blueberries.
"These data support the hypothesis that the antihypertensive bioactivity may be relevant to vasodilatory processes associated with specific flavonoid structural characteristics," wrote Dr. Rimm and his co-workers.
Dr. Rimm and his co-workers said that there exists a huge variety of flavonoid structures, and that the potential blood pressure-lowering effects were likely to be limited to a small number of "structurally similar compounds such as the catechol and 4’ hydroxy flavonoids."
"The underlying biological mechanisms by which flavonoids regulate blood pressure include the effects of flavonoids on vascular blood flow, vascular reactivity and glucose uptake," wrote the researchers. "Growing mechanistic evidence suggests that endothelial NO regulation rather than a general antioxidant effect (i.e., direct radical scavenging) is a major target for these compounds, and emerging data suggests that eNOS and NADHP oxidase activity are crucial sites of action for many flavonoids," they added.
"Our data suggested that several specific classes of flavonoids were associated with blood pressure reduction, specifically anthocyanins, which resulted in a 12% reduction in hypertension risk in multivariate analyses," wrote the researchers. "These data are important because anthocyanins are present in commonly consumed fruit, such as blueberries, cranberries and strawberries, which can be readily incorporated into the diet," they added.
American Journal of Clinical Nutrition 93: 338-347, 2010
Feb., 2011
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