Researchers examined data on blood pressure and cardiovascular disease as well as results from urine tests, looking for biomarkers of flavan-3-ol — a substance that indicates how much flavanol is in the diet — for more than 25,000 adults in the U.K. Systolic blood pressure — the “top number,” which shows how much pressure blood exerts on artery walls when the heart beats — was about 1.9 millimeters of mercury (mmHG) lower in men and about 2.5 mmHG lower in women with the highest flavanol intake than it was among their counterparts with the lowest flavanol intake. Differences in blood pressure associated with a high-flavanol diet were more pronounced in older adults and in people diagnosed with hypertension than in younger individuals and those with normal blood pressure, the study also found. “Our study shows for the first time that flavanols consumed as part of the normal diet are associated with lower blood pressure,” says senior study author Gunter Kuhnle of the department of food and nutritional sciences at the University of Reading in the U.K.
Pros and Cons of This Study Design
One advantage of this study is that it used urine tests to estimate how much flavonal people had in their diets — many other studies looking at health benefits of various eating patterns rely instead on food diaries or surveys that aren’t always an accurate picture of how people really eat, Kuhnle and colleagues write. In those cases, people often report healthier eating habits than they really have. Another strength of using biomarkers instead of self-reported dietary information is that the amount of flavanols in a particular food or drink can vary. For example, there can be anywhere from 10 to 330 milligrams (mg) of flavanols in 100 grams (g) of tea, the researchers point out. “Using nutritional biomarkers to estimate the intake of bioactive food compounds has long been seen as the gold standard for research, as it allows intake to be measured objectively,” Kuhnle says. The biggest limitation of the study is that results from this study in the U.K. — where tea is the main source of dietary flavanols — may not reflect what would happen in other populations where people tend to favor different foods and beverages. An additional limitation is that researchers looked at urine tests for flavanol intake at only a single point in time, and it’s possible that eating habits changed over time in ways that might impact blood pressure or cardiovascular disease risk, the researchers point out. It’s also worth noting that the study was funded by candymaker Mars Inc., where two of the authors work.
What Other Studies Say About Flavanols, Diet, and Blood Pressure
Earlier studies have found flavanols may help reduce stiffness in arteries, cholesterol, blood pressure, and the risk of developing or dying from cardiovascular disease, according to a review published in June 2018 in Molecular Aspects of Medicine. In particular, this review linked flavanols in cocoa and tea with these heart-healthy benefits. The blood pressure reduction seen with flavanols in the current study is comparable to what some earlier research found with two heart-healthy diets, the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) diet, Kuhnle says. A Mediterranean diet emphasizes consumption of fruit, vegetables, whole grains, fish, nuts, and olive oil and other healthy fats, according to the Mayo Clinic. It also advises dairy in moderation, and limited red and processed meats. The DASH diet takes these ideas further, by recommending the number of servings per week for different foods and limiting sodium intake. One study, published in 2013 in BMC Medicine, found that following a Mediterranean diet reduced diastolic blood pressure — the “bottom number,” which indicates how much pressure blood exerts on artery walls when the heart rests between beats — by 1.5 mmHg. This trial didn’t find a connection between the Mediterranean diet and systolic blood pressure, however. An older study, from the New England Journal of Medicine, found that when people tried to cut their sodium intake to the lowest level possible, following a DASH diet reduced systolic blood pressure more than eating in other ways — by 11.5 mmHg more for people with hypertension and by 7.1 mmHg more for people without hypertension. When people tried to reduce sodium intake from high levels to intermediate levels, the DASH diet reduced systolic blood pressure by 2.1 mmHg. “A sustained 2 mmHg reduction in blood pressure would have a large benefit on a population level — so from a public health perspective, that is a meaningful number,” says Deepak Bhatt, MD, MPH, executive director of interventional cardiovascular programs at Brigham and Women’s Hospital Heart & Vascular Center and a professor at Harvard Medical School in Boston. “However, for an individual, that would be less than what some people will experience with salt restriction or specifically with the Mediterranean or DASH diets,” says Dr. Bhatt, who wasn’t involved in the new flavanol study.
What Flavanol-Rich Foods Are Best for Lowering Blood Pressure?
Flavanols are part of a large family of compounds found in plants such as fruit, vegetables, beans, grains, and nuts, says Samantha Heller, RD, a senior clinical nutritionist at NYU Langone Health in New York City, who wasn’t involved in the current study. “In foods, these compounds have been found to confer many health benefits, including reducing the risk of certain diseases like cardiovascular disease, metabolic syndrome, and certain cancers,” Heller says. “They act as powerful antioxidants and anti-inflammatory agents.” To get the benefits of flavanols from sources such as cocoa and tea, it’s best to have unprocessed forms without lots of added sugar, cream, and other additives, Heller advises. This is especially true for cocoa and chocolate. People who want to use diet to help lower their blood pressure should think of increasing flavanols as part of an overall healthy eating pattern, Heller advises. “We eat foods, not single nutrients, and it is important to note that our dietary patterns play a big role in our intake of flavanols and other healthy plant compounds,” Heller says. “Adopting the DASH or Mediterranean dietary pattern is a great way of increasing one’s intake of flavanols as well as fiber, vitamins, minerals, and other healthy plant chemicals, and to help reduce blood pressure and the risk of other chronic diseases.”
