Null study on tart cherries blurs picture of polyphenols’ role in microbiome modulation
The new research was published in the journal Frontiers in Nutrition. It was the work of researchers associated with Ohio University and an institution in Doha, Qatar.
The authors noted that there has been an increasing amount of research looking into the anti inflammatory effects of polyphenols consumption and how these effects are mediated through the gut microbiome. Broadly speaking, polyphenols are poorly absorbed into the blood stream but do serve as food for bacteria further down in the digestive tract, giving rise to a host of theoretically beneficial metabolites.
They noted that significant results have been obtained in studies using polyphenols found in cocoa, red wine, powdered blueberries, grape seed extracts and tart cherries. But the findings have been mixed, they noted.
Four-arm study meant to test different forms of ingredient
One of confounding factors in research of this kind is the wide variety of forms of test materials used. Some studies have employed powdered forms of whole berries, while others have used extracts.
The authors of he present study sought to take this into account by using a four arm design for their double blind, randomized, placebo-controlled study that included 59 total subjects. One group consumed Montmorency tart cherry (MTC) concentrate juice, while another consumed a freeze dried form delivered in a capsule. Each of those arms had a corresponding placebo.
The trial was set to run for 30 days. Subjects were about evenly divided between men and women, and ranged from the early 20s to mid 40s in age. They displayed a range of body forms, from relatively lean to moderately overweight. They displayed a diversity of exercise habits, too, ranging from moderate daily exercise to levels well in excess of the minimum requirements recommended by health authorities. All had blood pressure readings in the normal range, however.
The participants visited the lab several times. After a consent visit, the participants maintained a food and physical activity questionnaire for 12 months before the supplementation period. They were not asked to alter their accustomed diets, which included some high fat diets and some that were low in fiber.
After that period baseline blood and fecal samples were taken, and again at 14 days and 30 days during the supplementation phase.
Factors that may have contributed to null results
The researchers were expecting to find that MTC supplementation would produce both shifts in the microbiome as well as a dampening down of inflammatory markers as well as benefits in the blood glucose management sphere. The failure to find these results could have come from using a healthy population that was not suffering from overly high levels of inflammation in the first place, as well as possibly not running the study long enough to find results that were of statistical significance.
“We found no significant alterations in the gut microbiome, and no significant impact of MTC supplementation on inflammation or glucose regulation. These results may partially be due to the use of a healthy population, who did not have inflammatory conditions and thus future work may need to focus on clinical populations. Additionally, time point measurements for the gut microbiome may have missed changes in bacterial composition, therefore additional time course analysis with more frequent measurements may be necessary to see if MTC has any impact on gut microbial composition,” they concluded.
Source: Frontiers in Nutrition
doi.org/10.3389/fnut.2021.733057
Thirty Days of Montmorency Tart Cherry Supplementation Has No Effect on Gut Microbiome Composition, Inflammation, or Glycemic Control in Healthy Adults
Authors: Hillman AR, Chrismas BCR
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