Microbial polyphenols in Mediterranean diet improve cardiovascular health

In Europe, cardiovascular diseases (CVDs) are one of the leading causes of premature deaths. CVDs are associated with an individual’s existing health conditions and habits, such as smoking, hypercholesterolemia, obesity, hypertension, unhealthy food habits, and diabetes mellitus.

Study: Association of microbiota polyphenols with cardiovascular health in the context of a Mediterranean diet. Image Credit: Antonina Vlasova / Shutterstock.com 

Background

The American Heart Association (AHA) proposed the ideal cardiovascular health (ICVH) score in 2010 to improve overall health and reduce deaths due to CVDs. The ICVH score is based on seven parameters, including ideal health-related behavioral patterns, including body mass index (BMI), healthy diet, appropriate physical activity, and non-smoking, as well as favorable health factors such as normal blood sugar, cholesterol, and blood pressure levels.

Cardiovascular health and diet are closely connected. Nutrients and phytochemicals obtained from diet play a significant role in preventing or incidence of CVDs.

Several studies have revealed that the Mediterranean diet (MedDiet), based on a high intake of nuts, legumes, fruits, vegetables, extra virgin olive oil, and moderate quantities of wine, reduces the risk of developing CVDs.

The MedDiet is rich in healthy fats and antioxidant bioactive molecules (e.g., polyphenols). Although polyphenols are known to improve cardiovascular health, their availability in the small intestine is low. Between 90-95% of polyphenols reach the large intestine, where they encounter enzymatic reactions catalyzed by the gut microbiome.

Post absorption, microbial phenolic metabolites (MPM) could be associated with various biological functions. However, limited studies have evaluated the benefits of MPM on cardiovascular health.

About the study

A recent Food Research International study has identified and quantified MPM in a subpopulation of the PREDIMED trial. Herein, the authors determine the association between MPM and MedDiet adherence and the effect on cardiovascular health in an elderly Mediterranean population.

PREDIMED is a multicenter-based, five-year clinical trial that examined the effect of the traditional MedDiet on the primary prevention of CVDs. In Spain, 7,447 participants were recruited between October 2003 and December 2010, with a key eligibility criterion being that participants must not have a history of CVD at baseline. The present study included 200 randomly selected participants from the PREDIMED-Hospital Clinic recruitment center in Barcelona, Spain. 

The current study applied a linear ion trap quadrupole-Orbitrap-mass spectrometer (LTQ-OrbitrapMS) for the analysis. This technique provided accurate structural information, which helped detect and quantify novel metabolic compounds. 

Study findings

The present cross-sectional sub-study of the PREDIMED trial revealed that higher urinary MPM scores were associated with greater MedDiet adherence and an improved ICVH score. Additionally, a robust inverse association was observed between urinary concentrations of urolithin B glucuronide (UBG) and low-density lipoprotein (LDL)-cholesterol. These findings strongly indicate that the MedDiet was linked with phenolic metabolites, which can improve cardiovascular health.

Previous studies have shown that the MedDiet can alter the microbiome ecosystem and the production of microbial metabolites in the gut. Interestingly, greater adherence to the MedDiet has been associated with increased Bacteroidetes, such as genus Prevotella, in the gut, which are involved with polyphenol metabolism.

None of the study participants achieved the highest recorded ICVH score, which implies that the entire cohort did not meet all seven-health metrics. This observation is consistent with a previous study within the PREDIMED trial, which reported only 0.3% of the cohort achieved scores of six and seven. This finding is not unnatural, as the PREDIMED trial includes the elderly Mediterranean population, which is usually at a higher risk of CVDs.

The current study also observed an association between multiple MPM and ICVH scores. In accordance with individual health parameters, blood glucose and diet were positively associated with the MPM score.

This association was also liked with MPM score and MedDiet adherence; however, individual MPM was unable to uplift the overall ICVH. Thus, together several phenolic metabolites appear to positively benefit cardiovascular health rather than individually.

Strengths and limitations

A vital strength of the current study is that it includes the analysis of biological samples, which offers reliable data on an individual’s metabolism. Furthermore, LTQ-Orbitrap enabled accurate elucidation and quantification of metabolites.

Despite its strengths, the current study has some limitations, such as the inclusion of only elderly Mediterranean individuals at a high risk of developing CVDs, reducing the generalization of the findings. In addition, due to the unavailability of fecal samples, the authors could not determine the participants’ microbiota composition.

Conclusions

The current study is the first to evaluate the association between urinary MPM, diet, and cardiovascular health using the LTQ-OrbitrapMS technique.

A robust association was observed between urinary MPM, MedDiet adherence, and a healthier cardiovascular status. Furthermore, the phenolic metabolites associated with MedDiet appear to offer beneficial properties for cardiovascular health.

In the future, more research is needed to better understand the effect of phenolic compounds in biological samples on the overall ICVH score.