July 8th is designated National Blueberry Day, and in recognition of this delicious fruit today’s post will examine a study just published in June on the effect of blueberry consumption on cardiovascular risk factors.

The US is the world’s largest producer of blueberries, producing more that twice the tonnage of blueberries annually than the 2nd largest producer, Canada. The largest blueberry producing state is Washington, followed by Georgia, Michigan and Oregon. Low bush or wild blueberries, and high bush or cultivated blueberries, are all native to North America. Many of the beneficial properties of blueberries are thought to be due to their anthocyanins. Anthocyanins are water-soluble pigments which may appear black, blue, purple or red. Plants rich in anthocyanins include black rice, blueberries and raspberries. Anthocyanins have anti-oxidant properties.

A research group from the UK and Harvard looked at the relationship between blueberry consumption and its effect if any on insulin resistance and markers of cardiometabolic function. A random controlled double blind study was performed, with 138 enrollees, randomly assigned to one of three groups- a group which consumed the dietary equivalent of one cup of fresh blueberries each day, a second group which consumed a dietary equivalent of 1/2 cup of fresh blueberries each day, while the third group consumed a placebo. It is important to note that the study subjects had all been diagnosed with metabolic syndrome and were overweight or obese. The study enrolled both men and women, ages 50-75.

The study lasted six months. The researchers discovered that while metabolic syndrome markers were not significantly changed by blueberry consumption, the group that consumed one cup of blueberries per day did show improvements in HDL (“good cholesterol”), endothelial function, and systemic arterial stiffness. It was estimated that a 13% reduction in future cardiovascular events was possible in the one cup per day group.

This is an important study, with one of the longer study periods (six months) completed to date. The study population had significant health issues, including metabolic syndrome and was older. Although the intervention did not change the insulin resistance numbers, it is possible that the study intervention was simply not long enough.

Metabolic syndrome is a cluster of conditions including elevated blood pressure, excessive fat around the waist, elevated triglyceride levels, and decreased HDL. Individuals with metabolic syndrome are at higher risk for heart attack and stroke, and metabolic syndrome is thought to be a precursor for Diabetes Mellitus Type 2.

Here is a well-designed study showing the benefits of a simple dietary intervention on metabolic syndrome. Next time you are considering something for dessert or a snack, put the cake, cookies and ice cream away and reach for blueberries instead. And buy local if possible, and support our farmers and propagators.

“There are eyes, to be sure, that give no more admission into the man than blueberries.”-    Ralph Waldo Emerson

(Source- American Journal of Clinical Nutrition 2019; 109)

This blog is a review of published medical and scientific literature, and should only be used for informational purposes. It does not constitute medical or health advice, nor does it create a physician-patient relationship with anyone. Discuss any health concerns with your personal physician.