Date of Award

2015

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Nutrition and Food Sciences

First Advisor

Kathleen J. Melanson

Abstract

Background

Indigestible, fermentable carbohydrates are bioactive dietary carbohydrates not digested by human enzymes but are fermented into short chain fatty acids and gases by colonic bacteria. These carbohydrates display prebiotic effects and may influence body mass index (BMI), glucose regulation, blood pressure, and blood cholesterol. However, intakes of fermentable carbohydrates have not been explored in the general US population and potential metabolic effects have not been well elucidated. The purpose of this cross-sectional study was to examine consumption of total fermentable carbohydrates and subclasses, oligosaccharides and polyols, in US college students (n=359, body fat= 25.4±9.3%, 83% female) and potential health differences between high and low consumers.

Methods

Intake of total fermentable carbohydrates, oligosaccharides, polyols and their subclasses were quantified by the Comprehensive Nutrition Assessment Questionnaire. Subjects were classified into lower median (LM) and upper median (UM) groups using median split for total grams consumed and grams consumed per 100kcal diet (g/1000kcal). Blood glucose and lipids were measured by Cholestech LDX®, body fat percent by BODPOD®, and waist circumference and blood pressure by standardized instruments and protocols. Median differences in dependent variables were analyzed of analysis of variance (ANOVA) and covariance (ANCOVA).

Results

Average fermentable carbohydrate intake was 8.0±4.9 grams with approximately even amounts coming from oligosaccharides and polyols. The LM for total grams of fermentable carbohydrate had higher BMI (24.3±4.6 vs. 23.3±3.7 kg/m2 respectively; p=.022), body fat percent (26.6±9.8 vs. 8.5%; p=0.16), and blood glucose (84±8 vs. 82±7mg/dL; p=0.24) than the respective UM. Using ANCOVA, the LM had higher systolic blood pressure than the UM (117±14 vs. 114±14mmHg; p=.028). Findings were similar with fermentable carbohydrate expressed as g/1000kcal. Using ANCOVA, the LM for OS as g/1000kcal had higher BMI (p=.021) and systolic blood pressure (p=.036) than the UM. The LM for polyols as g/1000kcal had higher diastolic blood pressure than the UM (p=.045).

Conclusion

Fermentable carbohydrate intake was low in this population. However, within this range, results suggest higher intake may impact BMI, blood glucose, and blood pressure in healthy US college students. Long term and mechanistic studies are needed to assess potential relationships, including in at-risk populations.

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