Date of Graduation

5-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Franck Carbonero

Committee Member

Luke R. Howard

Second Committee Member

Charles Rosenkrans

Third Committee Member

Jiangchao Zhao

Keywords

Fibers, Fruits and Vegetables, Gastrointestinal tract, Microbiota, Nutrition, Polyphenols

Abstract

Plant-based diets are primarily derived from plant sources, including fruits and vegetables. Such patterns are associated with health benefits by promoting general health and preventing many diseases and metabolic disorders. Fruits and vegetables are key sources of high-quality nutrients such as dietary fibers and polyphenols. Since they are rich in dietary fibers and polyphenols, whole fruits and vegetables represent unique and somewhat understudied modulators of the gut microbiota and its associated functions. This study aims to (i) investigate the impact of varying dilutions of cherry juices concentrate on the composition of the murine gut microbiota, (ii) investigate the impact of cranberry juice consumption on the bacterial composition of gut and vaginal microbiota in postmenopausal women, and (iii) investigate the impact of the amounts and botanical diversity of fruits and vegetables on gut microbiota profiles in healthy adults. Fecal samples were collected from mice consuming increasing tart cherry juice concentrations in their drinking water. A randomized, crossover controlled dietary intervention was conducted with cranberry juice and a matched control, and postmenopausal female volunteers provided stool and vaginal swabs for microbiota analyses. Two pilot studies looking at the impact of low and adequate intake of fruits and vegetables (SMART-Diet), as well as low versus high botanical diversity (SMART-Valid), were conducted at Colorado State University; stool samples were collected for gut microbiota analyses and short-chain fatty acids measurements. Microbial analyses were performed using Illumina following a dual-indexing 16S rRNA gene amplicon. Each dietary intervention resulted in distinct microbiota modulations and effects. Cherry juices consumption significantly increased the relative abundance of Akkermansia and Barnesiella and decreased the relative abundance of Bacteroides. Consumption of cranberry juice modulated the gut microbiota composition by elevating the relative abundance of Bifidobacterium, Clostridium XIVa members, Eggerthella, and Prevotella. Cranberry juice consumption also resulted in a beneficial impact on vaginal microbiota by decreasing the relative abundance of Streptococcus compared to a placebo. Finally, the SMART-Diet study showed that fruit and vegetable consumption resulted in a reduction of the Firmicutes/Bacteroidetes ratio whereas the SMART-Valid study showed an increase in the Firmicutes/Bacteroidetes ratio after fruit and vegetable consumption, and a significant increase in production of beneficial short-chain fatty acids. Our findings suggest that consumption of cherry juices, cranberry juice, and fruit and vegetable inclusive diets all have a beneficial impact on the composition of gut microbiota. This body of work is consistent with the emerging concept that whole foods should be considered rather than extracts when it comes to gut microbiota and microbiome studies. Human dietary studies with larger sample size are warranted by these suggested beneficial modulations.

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