In theNews: Anthocyanin-Containing Blueberries Reign Supreme

Good Reasons to Put ‘Purple’ on Your Plate

You’ve heard it before: eat more vegetables and fruit everyday, especially blueberries. It’s true that this tiny fruit can support health in big ways. Regular consumption of blueberries has been linked to a lower risk of heart disease and some cancers, and to better cognitive function as we age.

A new study confirms the importance of these berries (along with anthocyanin-containing fruits and a few others). Several other studies shed more light on one way they might be working to help keep blood vessels and the circulatory system functioning smoothly.

Certain Fruits Help Ward-Off Type 2 Diabetes, But Hold the Juice

Investigators have found that when it comes to fruit consumption and the risk of Type 2 diabetes, eating a greater variety rather than eating more is key (1). But are some fruits better than others at lowering that risk?

Harvard School of Public Health researchers set out to answer this question by looking at dietary data from more than 185,000 people, and following them over a 12-year period to see who developed Type 2.

After adjusting for other factors that can affect the chance of acquiring Type 2, they found that consuming blueberries, grapes, apples and grapefruit was associated with a significant reduction in risk, while other commonly eaten fruits such as oranges and peaches didn’t seem to have much of an impact.

Blueberries – which topped the risk-lowering list – resulted in a 26% risk reduction for those consuming 5 servings weekly.

One of the important findings of this study – the first to look at the effects of individual fruits on Type 2 risk – is that it’s best to skip the juice and go for the whole fruit instead. Greater consumption of fruit juices was associated with higher risk. People who consumed one or more servings of fruit juice daily increased their risk of developing Type 2 by as much as 21%.

Anthocyanins Help Keep Vessels Flexible

Epidemiologic studies suggest that increased consumption of anthocyanins (a type of flavonoid found in blueberries, bilberries and grapes) lowers the risk of cardiovascular disease, the most common cause of death among men and women. But how might these flavonoids be protective?

European researchers conducted two randomized, controlled trials, and report that anthocyanins may improve circulatory function in healthy men (2). The German and British collaborators investigated the effect of blueberry flavonoids on the function of the cells lining blood vessels, called the endothelium.

In the first study, they assessed the effects of various doses of anthocyanins on flow-mediated dilation, which is a way to measure the elasticity of blood vessels. As we age, blood vessels tend to lose their elasticity – a literal "hardening of the arteries" that is often a prelude to high blood pressure and cardiovascular disease.

The effective doses of anthocyanins they identified were equivalent to the amounts provided in about 3 ½ to 8 1/2 ounces of blueberries – a fairly easy amount to achieve. Flow mediated dilation increased after only an hour, and again at 6 hours.

The second study revealed that dose matters. The response in flow-mediated dilation improved with increasing dose, but not beyond the level of anthocyanins in 8 ½ ounces. These results suggest that regular consumption of anthocyanin-rich fruits can help maintain flexible vessels and healthy circulation.

References

1. Muraki I et al. Fruit consumption and risk of type 2 diabetes. Br Med J, Aug 28, 2013. [Epub ahead of print].
2. Rodriguez-Mateos A et al. Intake and time dependence of blueberry flavonoid-induced improvements in vascular function: A randomized, controlled, double-blind, crossover intervention study with mechanistic insights into biological activity. Am J Clin Nutr, Sept 4, 2013 [Epub ahead of print].