Monthly Archives: July 2019

Blueberry Juice May Lower Blood Pressure

July 8th is National Blueberry Day, and out of respect for this tasty fruit today’s post will review a study which examined the effects of wild blueberry juice in a group of adult women at high risk for diabetes mellitus type 2.

Both wild and cultivated blueberries are native to North America. Depending on altitude, latitude and weather the peak of the blueberry crop can vary from May to August. In the US there are many blueberry festivals which celebrate this delicious fruit. In places like Bethlehem PA, Burgaw NC and South Haven MI, among many others, blueberry lovers gather to celebrate.

The skins of the blueberries contain anthocyanins, which have anti-oxidant properties. Wild blueberries have one of the highest levels of anti-oxidants among fruits and vegetables. In the U.S., Maine is the largest producer of lowbush or wild blueberries, and produces over 100 million pounds annually.

A group from Canada and the U.S. performed a study examining the effects of wild blueberry juice on various cardiometabolic markers. The study population had at least two risk factors for type 2 diabetes, and thus were higher risk.

The study design was a randomized trial, with a placebo control. The subjects drank 240 ml of juice made from lowbush (wild) blueberries, while the control group drank a placebo beverage which was color and flavor matched to the blueberry juice. The blueberries were harvested from Prince Edward Island, Canada. Participants drank the blueberry juice daily for a week, followed by an eight day washout period. Following that workout period, the study group became the control group and vice versa.

Several cardiometabolic markers were monitored during the course of the study, such as serum cholesterol, HDL, LDL, triglycerides, glucose, endothelial function, c-reactive protein, serum amyloid, among others. Vital signs included blood pressure were also monitored.

19 participants, all women, completed the study. The researchers discovered that while the wild blueberry juice did not significantly change cardiometabolic markers, it did lower systolic blood pressure 4.8 mm Hg (4%) compared to the placebo group. While a 4.8 mm Hg reduction in systolic blood pressure may not sound substantial, it is estimated that a reduction of only 3 mm Hg may reduce mortality from heart disease and stroke by 5-8%. 

Drinking the blueberry juice for only 7 days was probably not long enough to effect any significant change on metabolic markers. A longer study seems reasonable given the promising results of this study. This does appear to be a low-risk way to improve one’s health. 

“The smallest seed of faith is better than the largest fruit of happiness.”– Henry David Thoreau

(Source- BMC Nutrition 2017 3:45)

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.




Blueberries and Metabolic Syndrome

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.