Date of Award

2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Health Sciences

Department

Nutrition and Food Sciences

First Advisor

Kathleen Melanson

Abstract

Excessive body fat and related dysmetabolic complications concern both emerging and developed countries. An important environmental cause of these conditions is the altered composition of gut microbiota, which is influenced by the host diet. A number of clinical trials target gut microbiome composition or functions with fermentable carbohydrates (FCs) to promote a healthier profile. Total dietary fiber, which includes both FC and non-fermentable carbohydrates, is considered a promising tool for the prevention of chronic diseases. This has led to significant changes in food and health recommendation with an increase in dietary fiber intake advised. However, reference to other FCs such as resistant starches, non-starch polysaccharides, polyols (lactitol, sorbitol, mannitol, etc.), soluble dietary fibers (SDF), and oligosaccharides (fructo- and galacto- oligosaccharides, etc.) are still lacking. Intakes of FC in free-living adults remain largely under-investigated, but the limited work to date suggests that they tend to be low. Determining overall dietary components and patterns associated with FCs might allow adjustment for diet in many future studies and can eventually help increase the habitual consumption of all FCs. Identifying the average consumption of all types of FCs and their associations with health outcome sin free-living populations might inform treatment practices that include all types of FCs to improve clinical outcomes and help to include them in dietary guidelines than just dietary fiber. Based on this background, the objectives, hypotheses, methods, and results of this dissertation are threefold:

Manuscript-1: The goal of this study was to analyze the association between the consumption of FCs and the total healthy eating index 2015 (HEI-2015) as well as HEI-2015 components. The study involves a US college student population, considering they are at the decisive stage of their dietary choices and at high risk of developing metabolic diseases. The Diet History Questionnaire-II (DHQ-II) was used to estimate dietary intake of FCs, and a simple HEI algorithm scoring method, which is a publicly available statistical code from the Division of Cancer Control and Population Sciences of the National Cancer Institute, was used to calculate the HEI-2015 total score and component scores. The relationship between FC intake and total HEI-2015 and the component score was assessed using a simple linear regression model. The result concluded that the higher total FCs intake was related to a higher HEI-2015 score and hence higher diet quality. Furthermore, the HEI adequacy components such as vegetables, sea/plant proteins, and fruits (total and whole) are associated with a higher intake of FCs, whereas total dairy showed an inverse association. Additionally, the association between moderation components and FC intake was not as strong as the adequacy components.

Manuscript-2: The purpose of this cross-sectional study was to examine the intake of quantified FCs (e.g., SDF and polyols, etc.), in US college students and to explore possible health differences between higher and lower consumers. Short-term laboratory studies show that FCs positively influence health through energy homeostasis., However, consumption of these FCs in college students has not been thoroughly investigated and their possible health benefits have not been well elucidated. The study included anthropometric, demographic, and dietary intake data from 587 students at the University of Rhode Island. A median split was used to classify higher and lower FC consumers. Stepwise multiple linear regression evaluated the differences in FC consumption and health outcomes while controlling for confounders. The results showed that the consumption of FC and subclasses (SDF and polyol) were low compared to the quantity used in intervention studies. Despite this fact, the results suggest that there was an inverse association between FC intake and blood glucose levels, percent body fat, blood pressure, and LDL-c levels in this population.

Manuscript-3: This cross-sectional study aimed to analyze the consumption of FCs and subclasses in plant-based (PT) and meat-based (MT) diet groups in US adults. We also compared the diet quality in PT-vs MT-based diet and explored whether diet quality alters the FC consumption in PT and MT diets. Prior research focused on the abundance of FCs in plant-based diets (e.g. vegan, vegetarian) and potential relations with health outcomes, however, limited evidence exists that compares the varying FC intake in PT vs MT diets. We hypothesized that perhaps FCs are related to a high-quality diet and not just plant-based diets. Data were collected through online surveys from participants who adhered to PT-diets (no consumption of animal flesh) and MT-diet (>7 times animal flesh/week) for at least the prior three months. An independent-sample-test was used to observe the mean difference in FC consumption in PT and MT diet groups and stepwise multiple regression was used to analyze the diet quality of these two diet groups. Study results suggest that eating better-quality diets, either plant-based or animal-based, was associated with higher consumption of FCs among US adults, and the lowest FC consumption was observed in low-quality MT-based diet groups.

Available for download on Sunday, February 13, 2022

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