Aging induces a number of disease-related changes to the cardiovascular system, including dysfunction of the endothelial cells that line blood vessels. Eating fruits and vegetables, which are rich in a variety of beneficial bioactive compounds, may slow cardiovascular aging. Investigators tested the effects of anthocyanin compounds from blueberries on flow-mediated dilation.

Flow-mediated dilation refers to the capacity of an artery to expand in response to increased blood flow. It is a widely accepted measure of vascular endothelial function, and poor flow-mediated dilation is a recognized feature of cardiovascular disease. Previous research has demonstrated a relationship between higher blueberry and strawberry intake and decreased risk of heart attack. Blueberries contain a number of bioactive compounds, including anthocyanins, procyanidins, flavonols, phenolic acids, and other phenolic compounds. The body subjects these compounds to a wide range of chemical processes, yielding bioactive metabolites. How these bioactive compounds differ in their effects on cardiovascular health is unclear.

The authors analyzed data from four studies involving a total of 60 participants and conducted a follow-up experiment in mice. In the first study, participants received one of five treatments on five separate days: a control beverage that mimicked blueberry juice; the control beverage with fiber added; the control beverage with added minerals and vitamins; pure anthocyanins; and a beverage made with freeze-dried blueberries. The investigators measured flow-mediated dilation at baseline and one, two, and six hours after participants ingested the beverages. In the second study, participants consumed capsules containing one of six concentrations of anthocyanins (0, 80, 160, 240, 320, or 480 milligrams) on six separate days. The investigators measured flow-mediated dilation at baseline and two and six hours after ingestion.

The third study measured the effects of long-term blueberry consumption. Participants consumed 11 grams of wild blueberry powder (equivalent to about four ounces of fresh blueberries) dissolved in water twice daily for 28 days. The investigators measured flow-mediated dilation at baseline and at seven, 14, 21, and 28 days of consumption. In the fourth study, participants consumed a drink containing 11 grams of wild blueberry powder or a control beverage twice daily for at least 28 days. The investigators measured flow-mediated dilation at baseline and two hours after ingestion on the first day of the intervention and after at least 28 days of consumption. For the follow-up experiment, investigators gave mice an injection of bioactive metabolites that they had identified from the previous human experiments and measured the effects on flow-mediated dilation.

Isolated anthocyanins improved endothelial function as measured by flow-mediated dilation in a dose-dependent manner, meaning that the effects were more robust as dose increased. The effects of these isolated anthocyanins were similar to those of wild blueberries. However, control beverages containing fiber, minerals, or vitamins and minerals had no significant effect on flow-mediated dilation. Twice daily wild blueberry consumption for one month also increased long-term flow-mediated dilation. Finally, injection of metabolites derived from the phenolic compounds found in blueberries improved flow-mediated dilation in mice.

These results demonstrate the beneficial effects of blueberries on cardiovascular health and elucidates the function of anthocyanin compounds as major mediators of vascular function in mice and humans.

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