Two apples a day lower serum cholesterol and improve cardiometabolic biomarkers in mildly hypercholesterolemic adults: a randomized, controlled, crossover trial

Healthy dietary patterns to reduce obesity-related metabolic disease: polyphenol-microbiome interactions unifying health effects across geography

PURPOSE OF REVIEW

The spread of the Western lifestyle across the globe has led to a pandemic in obesity-related metabolic disease. The Mediterranean diet (MedDiet), Okinawa diet (OkD) and Nordic diet, derived from very different regions of the world and culinary traditions, have a large whole plant food component and are associated with reduced disease risk. This review focuses on polyphenol : microbiome interactions as one possible common mechanistic driver linking the protective effects whole plant foods against metabolic disease across healthy dietary patterns irrespective of geography.

RECENT FINDINGS

Although mechanistic evidence in humans is still scarce, animal studies suggest that polyphenol or polyphenol rich foods induce changes within the gut microbiota and its metabolic output of trimethylamine N-oxide, short-chain fatty acids, bile acids and small phenolic acids. These cross-kingdom signaling molecules regulate mammalian lipid and glucose homeostasis, inflammation and energy storage or thermogenesis, physiological processes determining obesity-related metabolic and cardiovascular disease risk. However, it appears that where in the intestine metabolites are produced, the microbiota communities involved, and interactions between the metabolites themselves, can all influence physiological responses, highlighting the need for a greater understanding of the kinetics and site of production of microbial metabolites within the gut.

SUMMARY

Interactions between polyphenols and metabolites produced by the gut microbiota are emerging as a possible unifying protective mechanism underpinning diverse healthy dietary patterns signaling across culinary traditions, across geography and across domains of life.

Black Soybean Improves Vascular Function and Blood Pressure: A Randomized, Placebo Controlled, Crossover Trial in Humans

Vascular dysfunction and injurious stimuli such as oxidative stress are closely related to the risk of cardiovascular diseases (CVD). Dietary polyphenols are reported to exert beneficial effects in reducing the risk of CVD. Black soybean has been used as a nutritionally rich food and contains abundant polyphenols in its seed coat and grain. Black soybean has many beneficial physiological activities, and its prevention effects on CVD risk were reported mainly in animal experiments. In this study, we performed a randomized, single blind, placebo controlled, crossover trial to investigate the effect of black soybean consumption on the vascular function in healthy humans. Twenty-two healthy adults aged from 30 to 60 completed the four week trial with daily consumption of about a 40 g test material cookie containing 20 g roasted black soybean powder. Body composition, vascular function, biomarkers for oxidative stress, and polyphenol contents in the urine and the plasma were measured. After ingestion of the black soybean cookie, vascular function, which was evaluated by plethysmogram using a Pulse Analyzer®, was improved and systolic blood pressure was decreased. Moreover, nitric oxide levels in plasma and urine were increased, while an oxidative stress biomarker, 8-hydroxy-2'-deoxyguanosine level, in the plasma was decreased accompanied by an increase in the concentration of polyphenols derived from black soybean in plasma and urine. These results suggest that the antioxidant activity of black soybean polyphenols and an increase in the nitric oxide level may contribute to the improvement of vascular function. Thus, black soybean is an attractive food material for improvement of vascular function through decreasing oxidative stress by its potent antioxidant activity and increasing the nitric oxide level in healthy humans.

Two apples a day modulate human:microbiome co-metabolic processing of polyphenols, tyrosine and tryptophan

PURPOSE

Validated biomarkers of food intake (BFIs) have recently been suggested as a useful tool to assess adherence to dietary guidelines or compliance in human dietary interventions. Although many new candidate biomarkers have emerged in the last decades for different foods from metabolic profiling studies, the number of comprehensively validated biomarkers of food intake is limited. Apples are among the most frequently consumed fruits and a rich source of polyphenols and fibers, an important mediator for their health-protective properties.

METHODS

Using an untargeted metabolomics approach, we aimed to identify biomarkers of long-term apple intake and explore how apples impact on the human plasma and urine metabolite profiles. Forty mildly hypercholesterolemic volunteers consumed two whole apples or a sugar and energy-matched control beverage, daily for 8 weeks in a randomized, controlled, crossover intervention study. The metabolome in plasma and urine samples was analyzed via untargeted metabolomics.

RESULTS

We found 61 urine and 9 plasma metabolites being statistically significant after the whole apple intake compared to the control beverage, including several polyphenol metabolites that could be used as BFIs. Furthermore, we identified several endogenous indole and phenylacetyl-glutamine microbial metabolites significantly increasing in urine after apple consumption. The multiomic dataset allowed exploration of the correlations between metabolites modulated significantly by the dietary intervention and fecal microbiota species at genus level, showing interesting interactions between Granulicatella genus and phenyl-acetic acid metabolites. Phloretin glucuronide and phloretin glucuronide sulfate appeared promising biomarkers of apple intake; however, robustness, reliability and stability data are needed for full BFI validation.

CONCLUSION

The identified apple BFIs can be used in future studies to assess compliance and to explore their health effects after apple intake. Moreover, the identification of polyphenol microbial metabolites suggests that apple consumption mediates significant gut microbial metabolic activity which should be further explored.