A new study suggests you shouldn’t feel guilty about drinking red wine in moderation during the week – in fact, it could give you health benefits.
A team of experts in Germany and Northern Ireland looked at the link between consumption of flavonoids – found in red wine, among other food and drink – and blood pressure in a sample of nearly 1,000 German people.
They found drinking three standard-sized glasses (125ml) of red wine a week can lower blood pressure.
It’s thought that flavonoids promote the relaxation of muscles in our arteries, allowing them to widen and therefore improving blood flow.
However, the experts stress that if you don’t drink alcohol already, you shouldn’t start, and that boozers should always bear in mind official drinking guidelines.
Red grapes, their skin, their seeds and the wine derived from them are rich in beneficial compounds called flavonoids
According to the American Heart Association, which published the study, alcohol intake can be part of a healthy diet if consumed in moderation, meaning no more than one alcoholic drink a day for women and two alcohol drinks a day for men.
The NHS currently advises men and women not to drink more than 14 units a week on a regular basis. A large glass of wine (250ml) is around three units.
The study, published in the journal Hypertension, was conducted by scientists at Queen’s University Belfast and Kiel University in Germany.
According to the team, flavonoids – the abundant nutrients in fruits, vegetables, tea and other plant-based foods – appear to have a positive effect on blood pressure levels.
Flavonoids are broken down by the trillion-strong community of microorganisms in our gut, known as the microbiota.
‘Our gut microbiome plays a key role in metabolising flavonoids to enhance their cardioprotective effects,’ said study author Aedín Cassidy at Queen’s University in Belfast, Northern Ireland.
‘This study provides evidence to suggest these blood pressure-lowering effects are achievable with simple changes to the daily diet.’
Recent studies found a link between gut microbiota, the microorganisms in the human digestive tract, and cardiovascular disease (CVD), which is the leading cause of death worldwide.
Gut microbiota is highly variable between individuals, and there are reported differences in gut microbial compositions among people with and without CVD.
So the researchers wanted to investigate how variance within the gut microbiome could explain the link between intake of flavonoid-rich foods and blood pressure.
For the study, the experts recruited 904 adults between the ages of 25 and 82 from Germany’s PopGen biobank.
The PopGen biobank includes participants from a network of seven biobanks in Northern Germany.
Researchers evaluated the participants’ food intake, gut microbiome and blood pressure levels together with other clinical and molecular phenotyping at regular follow-up examinations.
Participants’ intake of flavonoid-rich foods during the previous year was calculated from a self-reported food questionnaire detailing the frequency and quantity eaten of 112 foods.
Flavonoid values were assigned to foods according to US Department of Agriculture data on flavonoid content in food.
Gut microbiome for participants was assessed by faecal bacterial DNA extracted from stool samples.
After an overnight fast, participants’ blood pressure levels were measured three times in three-minute intervals after an initial five-minute rest period.
Researchers also collected participants’ lifestyle information, including sex, age, smoking status, medication use and physical activity, as well as family history of coronary artery disease and the number of daily calories and fibre consumed.
As well as this, each participant’s height and weight was measured to calculate body mass index (BMI).
Flavonoids are essential nutritional compounds commonly found in fruits, vegetables, grains, bark, roots, stems, flowers, tea and wine
Participants who had the highest intake of flavonoid-rich foods, including red wine, apples and berries, had lower systolic blood pressure levels, as well as greater diversity in their gut microbiome than those who consumed the lowest levels of flavonoid-rich foods, they found.
Up to 15.2 per cent of the association between flavonoid-rich foods and systolic blood pressure could be explained by the diversity found in participants’ gut microbiome.
Meanwhile, eating 1.6 servings of berries per day (one serving equals 80 grams, or one cup) was associated with an average reduction in systolic blood pressure levels of 4.1 mm Hg, and about 12 per cent of the association was explained by gut microbiome factors.
Drinking 2.8 glasses (125 ml of wine per glass) of red wine a week was associated with an average of 3.7 mm Hg lower systolic blood pressure level, of which 15 per cent could be explained by the gut microbiome.
To put this into context, a systolic blood pressure of less than 120 mm Hg is considered ‘normal’, while 140 mm Hg or more is considered high.
The scientists now call for further research into how the gut microbiome mediates ‘the cardiovascular effects of flavonoid-rich foods’.
‘Our findings indicate future trials should look at participants according to metabolic profile in order to more accurately study the roles of metabolism and the gut microbiome in regulating the effects of flavonoids on blood pressure,’ said Cassidy.
‘A better understanding of the highly individual variability of flavonoid metabolism could very well explain why some people have greater cardiovascular protection benefits from flavonoid-rich foods than others.’
Pictured, the different categories of blood pressure, as detailed by the American Heart Association. A systolic blood pressure of less than 120 mm Hg is considered ‘normal’, while 140 mm Hg or more is considered high
The experts also note, however, that their findings cannot prove a direct cause and effect, and that the focus of this study was on specific foods rich in flavonoids, not all food and beverages with flavonoids.
Looked at in combination, previous studies into the health benefits of red wine have provided a confusing mix of results.
For example, a study published earlier this year by University of Oxford academics revealed drinking any amount of alcohol is harmful to the brain.
This study linked ‘moderate’ drinking to lower volume of grey matter found in the outermost layer of the brain, which is high in neural cell bodies and plays a major part in the central nervous system.
Prior to this, 2020 research found one small glass of red wine a day can stave off diseases such as Type 2 diabetes, osteoporosis, Alzheimer’s and heart disease.
And back in 2019, King’s College London scientists said drinking red wine helps maintain healthy cholesterol levels, keep a strong immune system and avoid obesity.
