A clinical trial where people ate a cup of blueberries each day for six months saw an improvement in several blood and health markers for cardiovascular disease.

Blueberries are much more than a deliciously sweet fruit. Medical science is looking into the health benefits that this powerhouse can give. Blueberries are high in plant chemicals called anthocyanins.

These anthocyanins are a type of flavonoid found naturally in a number of foods that have antioxidant and anti-inflammatory properties. They are also the pigments that give red, purple, and blue plants their rich colouring with the colour changing depending on the pH of the food.

Observational research points to regular blueberry eaters having lower rates of heart disease and type 2 diabetes. Such research though cannot conclusively prove that blueberries on their own are responsible for the health benefit. To date though, no longer-term clinical trials have been done to see if eating blueberries can reduce the risk of metabolic disease.

Filling the research gap, British researchers have just completed a six month randomised controlled trial to see if eating blueberries had any effect on the metabolic syndrome.

The metabolic syndrome is a collection of symptoms including high blood pressure, elevated blood sugar, excess fat around the abdomen and abnormal levels of blood fats. Someone with metabolic syndrome has a high risk of developing heart disease, stroke and diabetes.

A group of 115 volunteers with an average age of 62 took part in the study. All the people had metabolic syndrome. Each person was randomly assigned to eat either one cup (150 grams) or half a cup (75 grams) of blueberries each day. A third group was given a purple-coloured placebo food that had none of the anthocyanins found in blueberries.

After six months, it was the group of people eating a cup of blueberries each day who saw a clear health benefit. There was a significant improvement in their blood vascular health with better blood flow and less arterial ‘stiffness’.

Their ‘good’ HDL-cholesterol levels also went up, especially in people not taking statin medications. The favourable changes in metabolic health would be expected to translate into a fall in cardiovascular disease risk by between 11 and 15 per cent.

Implications

Blue is the new black in the world of nutrition research, and this latest research into delicious blueberries adds more evidence for the health benefits they can offer.

Last Reviewed: 19/04/2020

© Norman Swan Medical Communications.



References

For reference: Curtis PJ et al. Blueberries improve biomarkers of cardiometabolic function in participants with metabolic syndrome—results from a 6-month, double-blind, randomized controlled trial. American Journal of Clinical Nutrition 2019;109:1535-1545.

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