Berries, bacteria and blood pressure – what’s the link?

Berries, red wine, apples and pears could help lower blood pressure and the effects depend on your gut bacteria, according to new research


A type of chemical, called flavonoids, found in some plant foods could help lower blood pressure but seem to offer more protection to some people than to others. A new study from Queens University in Belfast and Kiel University in Germany have found that the difference could be down to differences in our gut microbiomes – the bacteria that live naturally in the gut and are involved in digestion. The study was published in the journals Hypertension and American Heart Association journal this October.

The researchers examined the gut bacteria of 900 people in Germany, who then answered questions about what they eat and had their blood pressure measured. Berries, red wine, apples and pears were all linked to lower systolic blood pressure (the top number) and the effects are thought to be due to a type of flavonoids, called anthocyanins, which have been linked to better heart health in the past. The individuals’ gut bacteria seemed to play an important step in the process, breaking down the plant compounds which then affect blood pressure.

The authors explained that the effects of food and bacteria seem to be a two-way street – what we eat affects the diversity and composition of our gut bacteria, and our gut bacteria affects the way our bodies break down and use foods. 

Lead author Professor Aedin Cassidy said in a statement from Queens: “Our gut microbiome plays a key role in metabolising flavonoids to enhance their cardioprotective effects, and this study provides evidence to suggest these blood pressure-lowering effects are achievable with simple changes to the daily diet.”

As can often be seen in dietary studies, the amounts are important. The study found blood 2.8 (250ml) glasses of red wine per week was linked to a 3.7mmHg reduction in systolic blood pressure, and 1.6portions of berries a day was linked to a 4.1mmHg reduction. 

Nirmala Markandu, Hypertension Nurse Specialist at Blood Pressure UK explained: “Unsurprisingly this study was very popular in the press due to the observed benefits of red wine, but it’s important to note the limitations of the study. It is a case-control study, which can show an association between red wine and lower blood pressure but does not prove or confirm benefits, as claimed in some headlines.

“As always, it’s important to drink alcohol only within the recommended limits. In terms of blood pressure control the best change you can make to your diet is to eat less salt, and eating a variety of fruit and veg including berries is always a good idea.

“It is very interesting to see how flavonoids might affect heart health and the observation that what we eat can change our gut bacteria. We look forward to seeing more research into how this could impact heart health.”