Consuming a diet that is rich in flavanol-rich foods and drinks, including tea, apples and berries, could help to lower blood pressure, according to the results of what University of Reading scientists claim is the first study, in thousands of U.K. residents, to use objective measures of diet. In contrast with most other studies investigating links between nutrition and health, which rely on study participants reporting their diets, the new study measured flavanol intake objectively using nutritional biomarkers, as indicators of dietary intake, metabolism or nutritional status, which are present in our blood.
The results showed that the difference in blood pressure between participants with the lowest 10% of flavanol intake and those with the highest 10% of intake was between 2 mmHg and 4 mmHg. This is comparable to meaningful changes in blood pressure observed in those following a Mediterranean diet or Dietary Approaches to Stop Hypertension (DASH) diet, they said. Notably, the effect was more pronounced in participants with hypertension.
Gunter Kuhnle, PhD, a nutritionist at the University of Reading who led the study, commented, “What this study gives us is an objective finding about the association between flavanols—found in tea and some fruits—and blood pressure. This research confirms the results from previous dietary intervention studies and shows that the same results can be achieved with a habitual diet rich in flavanols. In the British diet, the main sources are tea, cocoa, apples and berries.”
Kuhnle and colleagues report their findings in Scientific Reports, in a paper titled, “Biomarker-estimated flavan-3-ol intake is associated with lower blood pressure in cross-sectional analysis in EPIC Norfolk.”
High blood pressure is a leading disease risk factor globally, and cardiovascular disease (CVD) is a main cause of death, the authors pointed out. Changes in dietary habits have an important role to play in the prevention of CVD. Most dietary recommendations have focused on dietary patterns and macronutrients, but increased attention is now being focused on a group of non-nutritive dietary compounds, or bioactives, which are thought to play a physiological effect, and to impact on disease risk.
Flavan-3-ols are a major group of bioactive compounds that have been shown to improve vascular function in intervention studies, the authors noted. But while such compounds are of great interest for the development of dietary recommendation for the prevention of cardiovascular diseases, “ … there are currently no reliable data from observational studies, as the high variability in the flavan-3-ol content of food makes it difficult to estimate actual intake without nutritional biomarkers.”
For their reported study, the University of Reading team, together with collaborators at Cambridge University, the University of California Davis, and Mars, Inc, studied 25,618 participants from the European Prospective Investigation into Cancer (EPIC) Norfolk study. The study assessed flavanol intake through measurements of the recently developed biomarkers, designated gVLMB, and SERMB, which allow for estimating the intake of flavan-3-ols specifically. “As biomarkers for estimating flavan-3-ol intake were not available previously, we developed and evaluated at scale nutritional biomarkers to estimate the intake of flavan-3-ols in general, based on the flavan-3-ol-derived microbial metabolite 5-3′,4′-dihydroxyphenyl-γ-valerolactone (gVLM), and one specific for (–)-epicatechin intake, based on structurally related (–)-epicatechin metabolites (SREM),” the authors explained.
Their results showed that high flavan-3-ol intake was linked with a significantly lower systolic and diastolic blood pressure, and was inversely associated with blood lipids. Interestingly, the biggest difference was observed in participants with the highest blood pressure. This suggests if the general public increased its flavanol intake, there could be an overall reduction in cardiovascular disease incidence.
“The difference in systolic blood pressure observed here between low and high biomarker concentration in the cross-sectional analysis (approximately 2 mmHg) is similar to the reduction in blood pressure observed in dietary intervention studies,” the team noted. “This difference is comparable to those observed with a Mediterranean diet in the PREDIMED trial (1.5 mmHg) or a moderate reduction in salt intake in the DASH-Sodium trial (2.1 mmHg, high to intermediate sodium intake), and could have considerable impact on health at a population scale.”
A subgroup analyses further showed that the association between flavanol intake and blood pressure was strongest among participants at higher risk of developing cardiovascular diseases, in particular older participants and those with existing hypertension. This finding confirms the results from previous small-scale dietary intervention studies, the investigators noted. “The association between intake and blood pressure therefore follows a progressive model, where the strongest effect size is found in those with higher blood pressure.”
While noting some limitations to their work, the authors nevertheless stated that their results “show a significant and biomedically relevant inverse association between biomarkers of flavan-3-ol intake and blood pressure …” in the population studied, which is likely to have what they claimed is a considerable impact on a population scale. “In the context of an aging population and increased prevalence of chronic diseases, these findings hold promise for the prevention of cardiovascular disease through dietary approaches,” they concluded.
Hagen Schroeter, chief science officer at Mars Edge, further noted, “This study adds key insights to a growing body of evidence supporting the benefits of dietary flavanols in health and nutrition. But, perhaps even more exciting was the opportunity to apply objective biomarkers of flavanol intake at a large scale. This enabled the team to avoid the significant limitations that come with past approaches which rely on estimating intake based on self-reported food consumption data and the shortcomings of current food composition databases.”
Kuhnle added, “The methodology of the study is of equal importance. This is one of the largest ever studies to use nutritional biomarkers to investigate bioactive compounds. Using nutritional biomarkers to estimate intake of bioactive food compounds has long been seen as the gold standard for research, as it allows intake to be measured objectively. The development, validation and application of the biomarker was only possible because of the long-term commitment of all collaborators. In contrast to self-reported dietary data, nutritional biomarkers can address the huge variability in food composition. We can therefore confidently attribute the associations we observed to flavanol intake.”
