Title of Work

The association between dietary β-carotene intakes, serum β-carotene, anthropometric factors and dietary fat in United States adults

Document Type

Dissertation

Publication/Presentation Date

October 2020

Abstract

Obesity prevalence continues to increase in the United States (US), therefore, understanding preventative measures is increasingly important for population health. The US has one the world’s highest rates of overweight and obesity with at least 70% of adults categorized as overweight or obese, with an increasing prevalence of morbid obesity. Obesity is of concern because increasing rates are positively correlated with multiple comorbidities. The 2015-2020 Dietary Guidelines for Americans recommend adults consume approximately 2 cups of fruits and 2.5 cups of vegetables daily, as research has tied consumption to a reduced risk for many chronic diseases. Presumably, these recommendations are made because low serum carotenoid status, a marker of fruit and vegetable intake, is associated with increased cardiometabolic disease risk. Investigating the associations between the carotenoid β-carotene (BC) and obesity are pivotal in understanding obesity as a diet-related condition. This work is the first to assess multiple factors that might influence the association between dietary BC and serum BC concentrations utilizing population-based data collected in the US. Secondary data analysis of the 2003-2006 NHANES dataset, which utilized cross-sectional survey methods to obtain a unique collection of nationally-representative, health and nutrition-related data on non-institutionalized civilians in the US, was conducted. Weighted variables were created in SAS statistical software to accommodate the complex survey design. There is a normal distribution across sex, ethnicity, age, and body mass index (BMI), however, we natural log transformed serum BC concentrations, reported dietary BC, high-sensitivity C-reactive protein (hsCRP), and reported dietary lycopene due to skewing. Pearson correlation and partial correlation coefficients were used to assess variable correlation. Multivariable linear regression estimated relationships between serum BC concentrations and inflammation, reported dietary BC intake, BMI, total reported dietary fat intake, and total reported dietary fatty acid (FA) intakes. Notable associations were present between serum BC concentrations and BMI, hsCRP, reported dietary BC intakes, android body fat percentage, gynoid body fat percentage, saturated FAs, monounsaturated FAs, and polyunsaturated FAs. The findings of this project suggest a protective effect of increased serum BC concentrations against low-grade, systemic inflammation often associated with adipose tissue dysfunction present in obese individuals. The association present between serum BC and anthropometric factors related to higher adiposity, suggests individuals with an increased BMI and/or body fat percentage may have a greater risk of lower serum BC concentrations despite dietary BC intake. Additionally, dietary FA, polyunsaturated FA alpha-linolenic acid, is associated with increased BC in circulation. Moreover, the inverse association present between serum BC and other specific fatty acid classes suggests there may be multiple post-digestion factors affecting serum BC concentrations.

Department

Food Science and Nutrition

Degree

Doctor of Philosophy

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