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August 7, 2018

For a Healthy Gut, Put a Cherry on Top

Source: Flickr

  • A growing body of scientific evidence continues to show that improving the health of the gut microbiome may be a simple, yet highly effective way to prevent disease and maintain a healthy lifestyle. Due to its potential role in maintaining digestive health, as well as its impact on immunity, heart health, blood sugar control, weight management, and even brain health the microbiome has been the focus of multiple studies and holds great promise, especially related to personalized nutrition. Now, new evidence from investigators at the University of Arkansas suggests that Montmorency tart cherries can be added to the list of gut-friendly foods and may play an important role in improving gut health.

    Findings from the new study were published today in the Journal of Nutritional Biochemistry through an article titled “Impact of tart cherries polyphenols on the human gut microbiota and phenolic metabolites in vitro and in vivo.” While previous studies on Montmorency tart cherries have ranged from heart health and exercise recovery to sleep, this is the first study to explore the potential gut health benefits. The researchers speculate that it may be due to the polyphenols (anthocyanins and other flavonoids) in Montmorency tart cherries, the varietal of tart cherries grown in the U.S. Polyphenols in plant-based foods are broken down by microbes to stimulate the growth of beneficial bacteria.

    "Montmorency tart cherries were a logical food to study due to their unique composition of polyphenols, including chlorogenic acids," explains senior study investigator Franck Carbonero, Ph.D., assistant professor in the department of food science at the University of Arkansas. "Our results suggest that the unique polyphenol mixture in tart cherries may help positively shape the gut microbiome, which could potentially have far-reaching health implications."

    Researchers conducted both human and laboratory experiments to determine the impact of Montmorency tart cherries on the microbiome. In the human trial, nine healthy adults, 23-30 years old, drank 8 ounces of Montmorency tart cherry juice (from concentrate) daily for five days. These individuals were nonsmokers and had not taken antibiotics (which can affect the microbiome) in the 12 weeks prior and during the study. Using stool samples, the participants' microbiome was analyzed before and after the dietary intervention, and food frequency questionnaires were used to evaluate their overall diet.

    Concurrently, laboratory experiments were set up to mimic the conditions within the human digestive system, specifically the stomach, small intestine, and three regions of the colon, to study how polyphenols are broken down and absorbed. This process of breakdown and absorption can have a significant impact on the body's ability to use the beneficial bioactive compounds in plant-based foods. The researchers tested U.S.-grown Montmorency tart cherries, European tart cherries, sweet cherries, apricots, and isolated polyphenols in each simulated region of the digestive tract. They analyzed changes in the mix of bacteria and how these bacteria helped digest the polyphenols over time.

    In the human analysis, the microbiome was positively altered (primarily measured by the increase in good bacteria) after just five days of drinking Montmorency tart cherry concentrate, although there were strikingly different responses due to the participants' initial microbiome composition. Individuals who ate a more Western diet (low in fruits, vegetables, and fiber) potentially had a lower ability to metabolize polyphenols, thereby reducing bioavailability and any potential health benefits in the tart cherries. Remarkably, in these subjects, instead of Bifidobacterium, Collinsella were the beneficial polyphenol-degrading bacteria stimulated. The individuals who ate a more plant-based diet, with higher intakes of carbohydrates and fiber, responded with an increase in Bacteroides and Bifidobacterium, presumably because of the specific combination of polysaccharides and polyphenols.

    While more research is needed, these results suggest individuals consuming a more plant-based diet may have a mix of gut bacteria that respond more positively and rapidly to tart cherry consumption. Individuals consuming a more Western diet that is lower in carbohydrates and fiber may have a lower/different ability to metabolize polyphenols, thereby altering bioavailability and any potential health benefits.

    Interestingly, the in vitro studies found that pure polyphenols characteristics of tart cherries increased the amount of Bifidobacterium. However, when concentrated juices were fermented, this bifidogenic effect appeared to be leveled out by the larger increase of polysaccharides utilizing bacteria. Somewhat surprisingly, however, chemistry analyses showed that tart cherries polyphenols were not completely converted to smaller phenolic metabolites, suggesting that the full diversity of bacterial species in the human gut is required for efficient breakdown of the polyphenols in tart cherries.

    These results help build the foundation for future research and suggest that Montmorency tart cherries can play a role in positively shaping the microbiome and maintaining gut health.

    “These data confirm that gut microbiota metabolism, in particular, the potential existence of different metabotypes, needs to be considered in studies attempting to link tart cherries consumption and health,” the authors concluded.

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