Prebiotic effects of a cranberry beverage in a randomized, placebo-controlled, crossover clinical trial
Date
2022-05
Authors
Zhao, Jingcheng
Major Professor
Advisor
White, Wendy
Wannemuehler, Michael
Hollis, James
Shi, Xiaolei
Lanningham-Foster, Lorraine
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Abstract
The gut microbiota is essential in human physiology and dysbiosis of the gut microbiota may be associated with several disorders and diseases, including obesity, inflammatory bowel disease (IBD), and type 2 diabetes. Diet is one of the major factors affecting the structure of the gut microbiota. Prebiotics, such as plant phytochemicals, are among many dietary compounds that confer health benefits on the host. Cranberries are rich in anthocyanins, flavonols, proanthocyanidins (PACs) but most of them are poorly absorbed. As a result, these cranberry components have the potential to interact with gut microbiota and exert prebiotic effects. Emerging evidence from studies in animal models and prospective clinical trials indicates that cranberry products, such as cranberry powder and dried cranberries, have an impact on the gut microbiota. Nevertheless, randomized controlled clinical trials with a well-controlled diet are needed to confirm these observations and extend our knowledge regarding how enriching the diet with cranberries affects the composition and function of the gut microbiota. In this study, we implemented a dietary intervention in the form of a cranberry beverage to modulate the gut microbiota in healthy adults. The primary objective was to explore the change of the gut microbiota after the consumption of a milled whole cranberry beverage compared with a placebo beverage. Ancillary goals were to study the effects of the cranberry beverage on gastrointestinal (GI) symptoms and bacterial metabolites, specifically short chain fatty acids (SCFAs).
In this study, adults (n = 17; ages 18-42 y; BMI 30.5 ± 3.1 kg/m2) were enrolled in a 60-d, two-period, randomized, placebo-controlled, crossover clinical trial. Throughout the study, participants were fed a standardized 10-d cycle menu on site. During each 20-d treatment period, participants consumed twice daily a milled whole cranberry or placebo beverage (240 mL per serving). Treatment periods were preceded by 10-d run-in periods on the controlled study diet. Participants completed a daily GI diary recording number of bowel movements, ease of stool passage, stool consistency, and GI tolerance (cramping, distension, and flatulence). Compared with the placebo beverage, the cranberry beverage decreased the incidence of moderate and severe flatulence (P = 0.02). Fecal samples were collected before and after the dietary interventions for bacterial compositional analysis by 16S rRNA gene sequencing and SCFA analysis by using UPLC-MS/MS. Among the 68 samples analyzed, an unclassified member of Coriobacteriaceae family was significantly more abundant after participants consumed the cranberry beverage as compared with the placebo beverage (ANCOM W > 0.7). In contrast, the clinically-important pathogen Clostridium perfringens was present after consumption of the placebo beverage but was a structural zero (not present) after consumption of the cranberry beverage. No treatment effects were found in alpha diversity, beta diversity, or SCFA concentrations.
In conclusion, the study described in this dissertation showed that a milled whole cranberry beverage has a prebiotic effect on the gut microbiota by increasing the growth of beneficial bacteria and inhibiting the growth of pathogenic bacteria. Furthermore, twice daily consumption of a whole cranberry beverage may contribute to the alleviation of GI symptoms. Further studies with a larger sample size are warranted to validate to which extent the results obtained in this study could be translated into clinical applications. Future studies are needed to explore other metabolites from the bacterial fermentation of cranberry components. In vitro studies or animal studies with germ-free mice are necessary to investigate the mechanisms by which the detected beneficial bacteria in this study contribute to health improvement.
Series Number
Journal Issue
Is Version Of
Versions
Series
Academic or Administrative Unit
Type
dissertation