Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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Description
High fiber diets have been associated with improved cardiometabolic health with specific efforts to lower circulating levels of low-density lipoprotein (LDL cholesterol). Whole grain and grain-based foods are major contributors of dietary fiber in the American diet, of which wheat has been extensively studied. Corn, however, has not been well studied for its cholesterol-lowering properties. Further, the mechanisms by which grains improve cardiometabolic health require further exploration with regard to the human microbiome. The objective of this single-blind randomized controlled, crossover trial was to assess the impact of three different corn flours (whole grain, refined, and bran-enhanced refined flour mixture) on serum LDL cholesterol and the gut microbiota diversity and composition. Twenty-three participants were recruited, between the ages of 18-70 with hypercholesterolemia (Male = 10, Female = 13, LDL >120 mg/dL) who were not taking any cholesterol-lowering medications. Participants consumed each flour mixture for 4 weeks prepared as muffins and pita breads. At the beginning and end of each 4-week period serum for cholesterol assessment, anthropometrics, and stool samples were obtained. Serum cholesterol was assessed using a clinical analyzer. Stool samples were processed, and microbial DNA extracted and sequenced based on the 16S rRNA gene. A generalized linear model demonstrated a significant treatment effect (p=0.016) on LDL cholesterol and explained a majority of the variance (R-squared= 0.89). Post hoc tests revealed bran-enhanced refined flour had a significant effect on cholesterol in comparison to whole grain flour (p=0.001). No statistically significant differences were observed for gut microbial community composition (Jaccard and weighted Unifrac) after corn consumption. However, relative abundance analysis (LEfSE) identified Mycobacterium celatum (p=0.048 FDR=0.975) as a potential marker of post-corn consumption with this microbe being differentially less abundant following bran-enhanced flour treatment. These data suggest that corn flour consumption may be beneficial for individuals with hypercholesterolemia but the role of gut microbiota in this relationship requires further exploration, especially given the small sample size. Further research and analysis of a fully powered cohort is needed to more accurately describe the associations and potential mechanisms of corn-derived dietary fiber on circulating LDL cholesterol and the gut microbiota.
ContributorsWilson, Shannon L (Author) / Whisner, Corrie M (Thesis advisor) / Sears, Dorothy (Committee member) / Buman, Matthew (Committee member) / Dickinson, Jared (Committee member) / Zhu, Qiyun (Committee member) / Arizona State University (Publisher)
Created2022
Description
Healthy lifestyle behaviors including quality nutrition have been shown to successfully prevent chronic disease or minimize symptoms. However, many physicians lack the knowledge and skills to provide adequate nutrition counseling and education for their patients. A major component of this problem is that medical schools are not required to teach nutrition education. The purpose of this feasibility study was to compare the changes in the perceived importance of nutrition in the medical field in medical students before and after participating in a week-long interactive nutrition course in order to determine if a week-long course can positively influence students’ perceptions of nutrition. Ultimately by changing these perceptions, medical students may be able to better help patients prevent chronic disease. The participants were first year medical students at the Mayo Clinic School of Medicine (Scottsdale, AZ) who chose to participate in this medical school “Selective”. The study included a five-day curriculum of case-studies, lectures from specialized health professionals, and a cooking class led by a chef who trained in France. An anonymous pre- and post-study questionnaire with five-point Likert scale questions was used to measure changes in attitudes. The data suggest that students’ perceptions regarding the importance and relevance of nutrition in the medical shifted slightly more positive after attending this Selective, although these shifts in attitude were not statistically significant. Limitations of this study include a small sample size and selection bias, which may have decreased the potential of having significant results. Both of these factors also make the results of this study less generalizable to all medical students. This study supports the need for a larger experimental study of a similar design to verify that an interactive, evidence-based nutrition class and culinary experience increases medical students’ positive perceptions of nutrition in the medical field.
ContributorsBaum, Makenna (Author) / Johnston, Carol (Thesis advisor) / Levinson, Simin (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2020
Description
First year college students have been identified as a vulnerable population for weight gain and the onset of overweight and obesity. Research regarding the gut microbiome has identified differences in the microbial composition of overweight and obese individuals compared to normal weight individuals. Dietary components like dietary fibers, act as prebiotics, or fermentable substrate, that the gut microbiota use for metabolic functions including the production of short-chain fatty acids. The objective of this longitudinal, observational study was to assess changes in the gut microbiota over time in relation to changes in fiber consumption in healthy college students at a large a southwestern university (n=137). Anthropometric and fecal samples were collected at the beginning and end of the fall and spring semesters between August 2015 and May 2016. Both alpha, within sample, diversity and beta, between sample, diversity of participant gut microbes were assessed longitudinally using non-parametric pairwise (pre-post) comparisons and linear mixed effect (LME) models which also adjusted for covariates and accounted for time as a random effect. Alpha and beta diversity were also explored using LME first difference metrics and LME first distance metrics, respectively, to understand rates of change over time in microbial richness/phylogeny and community structure. Pre-post comparisons of Shannon Diversity and Faith’s PD were not significantly different within participant groups of fiber change (Shannon diversity, p=0.96 and Faith’s PD, p=0.66). Beta diversity pairwise comparisons also did not differ by fiber consumption groups (Unweighted UniFrac p=0.182 and Bray Curtis p=0.657). Similarly, none of the LME models suggested significant associations between dietary fiber consumption and metrics of alpha and beta diversity. Overall, data from this study indicates that small changes in fiber consumption among a free-living population did not have an impact on gut microbial richness, phylogeny or community structure. This may have been due to the low intake (~15 g/d) of fiber. Further study is needed to fully elucidate the role that fiber plays in the diversity and composition of the gut microbiota, especially when delivered from a variety of food sources rather than fiber supplements.
ContributorsLolley, Sarah (Author) / Whisner, Corrie (Thesis advisor) / Sears, Dorothy (Committee member) / Shepard, Christina (Committee member) / Arizona State University (Publisher)
Created2020
Description
ABSTRACT
Background. College students’ modifiable health behaviors, including unhealthful eating patterns, predispose them to risk for future cardiometabolic conditions.
Purpose. This novel 8-week randomized control parallel-arm study compared the effects of a daily 18-hour Time-Restricted Feeding protocol vs. an 8-hour fast on diet quality in college students. Secondary outcomes were resting morning blood pressure, biomarkers of glucose regulation, biomarkers of lipid metabolism, and anthropometric measures.
Methods. Eighteen healthy college students (age = 23 ± 4 years; BMI = 23.2 ± 2.3 kg/m2; MET = 58.8 ± 32.9 min/wk) completed this study. Participants were randomized to a daily 18-hour fasting protocol (Intervention; n = 8) or a daily 8-hour fasting protocol (Control; n = 10) for eight weeks. One ‘cheat’ day was permitted each week. Outcomes were measured at weeks 0 (baseline), 4, and 8. A non-parametric Mann Whitney U test was used to compare the week 4 change from baseline between groups. Statistical significance was set at p≤0.05.
Results. Diet quality (p = 0.030) and body weight (p = 0.016) improved from baseline to week 4 for the INV group in comparison to the CON group. The data suggest these improvements may be related to reductions in snacking frequency and increased breakfast consumption. Fasting blood glucose and hip circumference tended to improve for the INV group in comparison to the CON group (p = 0.091 and p = 0.100). However, saturated fat intake tended to increase in the INV group in comparison to the CON group (p = 0.064). Finally, there were no treatment differences between groups (p>0.05) for the 4-week change in total calories, dietary vitamin C, added sugars, resting systolic blood pressure, resting diastolic blood pressure, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), low-density lipoprotein (LDL) cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, waist circumference, or MET.
Conclusion. These data, although preliminary, suggest that the 18-hour fasting protocol was effective for improving diet quality and reducing weight in comparison to the 8-hour fasting protocol in healthy college students. Future intervention trials will need to confirm these findings and determine the long-term relevance of these improvements for health outcomes.
Background. College students’ modifiable health behaviors, including unhealthful eating patterns, predispose them to risk for future cardiometabolic conditions.
Purpose. This novel 8-week randomized control parallel-arm study compared the effects of a daily 18-hour Time-Restricted Feeding protocol vs. an 8-hour fast on diet quality in college students. Secondary outcomes were resting morning blood pressure, biomarkers of glucose regulation, biomarkers of lipid metabolism, and anthropometric measures.
Methods. Eighteen healthy college students (age = 23 ± 4 years; BMI = 23.2 ± 2.3 kg/m2; MET = 58.8 ± 32.9 min/wk) completed this study. Participants were randomized to a daily 18-hour fasting protocol (Intervention; n = 8) or a daily 8-hour fasting protocol (Control; n = 10) for eight weeks. One ‘cheat’ day was permitted each week. Outcomes were measured at weeks 0 (baseline), 4, and 8. A non-parametric Mann Whitney U test was used to compare the week 4 change from baseline between groups. Statistical significance was set at p≤0.05.
Results. Diet quality (p = 0.030) and body weight (p = 0.016) improved from baseline to week 4 for the INV group in comparison to the CON group. The data suggest these improvements may be related to reductions in snacking frequency and increased breakfast consumption. Fasting blood glucose and hip circumference tended to improve for the INV group in comparison to the CON group (p = 0.091 and p = 0.100). However, saturated fat intake tended to increase in the INV group in comparison to the CON group (p = 0.064). Finally, there were no treatment differences between groups (p>0.05) for the 4-week change in total calories, dietary vitamin C, added sugars, resting systolic blood pressure, resting diastolic blood pressure, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), low-density lipoprotein (LDL) cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, waist circumference, or MET.
Conclusion. These data, although preliminary, suggest that the 18-hour fasting protocol was effective for improving diet quality and reducing weight in comparison to the 8-hour fasting protocol in healthy college students. Future intervention trials will need to confirm these findings and determine the long-term relevance of these improvements for health outcomes.
ContributorsMayra, Selicia (Author) / Johnston, Carol (Thesis advisor) / Sears, Dorothy (Committee member) / Swan, Pamela (Committee member) / Sweazea, Karen (Committee member) / Wharton, Christopher (Christopher Mack), 1977- (Committee member) / Arizona State University (Publisher)
Created2020
Description
The popularity of intermittent fasting has grown in recent years and is a commonly discussed diet topic on the internet and social media. Time-restricted feeding (TRF) is one particular intermittent fasting regime that allows participants to pick windows of time per day in which they can eat or fast. While current randomized controlled trials show positive effects of TRF on weight loss, body composition, glucose, insulin, and blood pressure, there is a gap in the literature of the its effect on cognition although animal studies suggest a positive effect. The purpose of this 8-week randomized controlled trial was to investigate the effect of 18-hour time-restricted feeding on healthy, Arizona State university students. Students (n= 29) were recruited by the research team and were randomized to either an 18-hour intervention (INV) group or an 8-hour control (CON) group. INV participants were instructed to consume food within the first hour of waking and cease their eating period after 6 hours to begin their 18-hour fast. Participants were not given any other dietary restrictions and were allowed to eat ad libitum during their eating periods. Cognitive tests (Stroop Test and Trail Making Test) and blood draws were taken at baseline, week 4, and week 8. The present study demonstrated high attrition, with 7 participants dropping out of the study after their baseline visit. Interruption of the COVID-19 pandemic also impacted the data analysis, with the removal of week 8 data. Despite limitations, statistically significant differences between the INV group and CON group were seen in the Trail Making Test B at week 4 (p= 0.031). Statistically significant differences were not seen in any of the other cognitive outcomes measured (Stroop Test, Trail Making Test A, serum BDNF, serum ketones). However, a significant inverse relationship was seen between serum ketones and Trail Making Test B. In conclusion, this study suggests that TRF may have a favorable effect on cognitive acuity among university students.
ContributorsKravat, Natalie (Author) / Johnston, Carol (Thesis advisor) / Gu, Haiwei (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2021
Description
Historically, researchers in the gut microbiome have deemed the composition of the microbiome as being adult by the age of two. However, recent studies have contradicted this, demonstrating statistically significant differences in the microbiome even through childhood and adolescence. This difference is important in the field of microbiome research, particularly in studies examining this relationship with weight, because even though there have been significant associations between the gut microbiome and weight, they have been largely studied in adults. The freshman year of college is an interesting time to study this relationship in younger populations, due to the lifestyle changes that make them vulnerable to weight gain. This study included N=139 participants, a majority female (N=97, 69.8%), white (N=59, 42.4%), and non-Hispanic (N=89, 64%). Participants were only included in this analysis if they gave 2 or more fecal samples over the 4 timepoint study. Samples were sequenced using the Illumina MiSeq instrument after polymerase chain reaction (PCR) amplification was performed on the V4 region of the 16S rRNA gene sequence. Statistical analysis was performed using the longitudinal plugin of QIIME2. Results demonstrate that low abundance features seemed to drive a majority of the differences in variability between those who maintained their weight over the course of the study and those who gained weight. This was demonstrated through many significant Unweighted UniFrac results with corresponding nonsignificant Weighted UniFrac data. This study demonstrated that changes in lower abundance features may have driven the significant differences in weight status in this study. This study emphasized the importance of low abundance features and how this relates to changes in weight status during a period of major lifestyle changes. Further work is needed to confirm these findings and explore how gut microbes change in free-living individuals gaining weight over time.
ContributorsAhern, Mary (Author) / Whisner, Corrie (Thesis advisor) / Bruening, Meg (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2021
Associations Between Rapid Infant Weight Gain, Infant Feeding Practice and the Infant Gut Microbiome
Description
Background: Rapid infant weight gain (RWG) by six months of age has been identified as one of the earliest indicators of childhood obesity. Previous research suggests that exclusive breastfeeding over formula feeding may serve a protective effect from RWG. In addition, the makeup of the infant gut microbiome may influence RWG as differences in feeding practices have been shown to alter the bacterial makeup of the gut, potentially impacting energy metabolism. However, little research has been conducted investigating the potential relationships between RWG, infant feeding practices, and the infant gut microbiome.Methods: This study was a pilot study, which included 31 mother-infant dyads who were primarily recruited from Women, Infant, and Children’s Supplemental Nutrition Program (WIC) clinics and by word of mouth in the Southwestern United States. Participants were followed over six months, with study staff conducting home study visits four times (pregnancy, two days postpartum, three weeks and six months). Mothers who participated in this study were majority White (n=40.6%), non-Hispanic or Latino (67.7%), and obtained a graduate degree (n=22.6%). Participants were included in this analysis (n=22) if they provided at least two infant fecal samples, and the study staff were able to collect infant anthropometric data at the three-week and six-month study visits. Microbial DNA from fecal samples was sequenced using the Illumina MiSeq instrument after polymerase chain reaction (PCR) amplification was performed on the V4 region of the 16S rRNA gene sequence. Statistical analysis was performed using the QIIME2 longitudinal plug-in.
Results: Results of this study suggested a significant difference in weighted UniFrac between infants who were exclusively breastfed and formula-fed from birth to three weeks of age. Additionally, an exploratory statistical method identified family Prevotellaceae as a potentially volatile microbe; however, this model failed to reach significance for either RWG or mode of feeding. Overall, no additional alpha or beta diversity metrics or differential abundance of microbes by either RWG or feeding practice group was found in this study.
Conclusion: Future research is warranted to further explore potential connections between RWG, infant feeding practices, and the infant gut microbiome in a longitudinal study with a larger sample size.
ContributorsToffoli, Samantha (Author) / Whisner, Corrie (Thesis advisor) / Bruening, Meg (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2021
Description
Background: Despite research aimed at understanding the mechanisms of metabolic syndrome (MetS), this prevalence continues to rise. Recent literature indicates that dietary fiber may offer prevention and management of MetS in various studies involving human and animal subjects. Objective: This six-week study aimed to test the efficacy of a novel fiber-rich complex in young male Sprague-Dawley rats by examining the effects on high-fat diet-induced weight gain, adiposity, high blood sugar, lipid imbalance, and oxidative stress.
Methods: 24 six-week-old male Sprague Dawley rats were randomly assigned into three diet groups (regular chow, high-fat, or high-fat + fiber) and fed for six weeks. Blood from the animals was collected at weeks 0, 3, and 6 for fasting blood glucose (FBG) analysis and at weeks 0 and 6 for lipid profile assessment. Body mass was weighed weekly. Organ mass, nasoanal, and tail length were measured at week 6. Findings were considered significant at p-value < 0.05. Data collected at week 6 were analyzed by one-way ANOVA, whereas data collected at multiple time points were analyzed by two-way ANOVA with diet and time as factors. Student-Newman-Keuls posthoc analyses were used to compare differences between and within groups.
Results: No significant differences were found in the size of rats fed each diet as measured by tail length (p = 0.599) or nasoanal length (p = 0.875). Abdominal circumference was not significantly different (p = 0.477). There were no significant differences between groups in fasting whole blood HDL cholesterol (p = 0.297), fasting whole blood HDL triglycerides (p = 0.624), plasma total triglycerides (p = 0.137), or beta-hydroxybutyrate (p=0.185) after six weeks of each dietary treatment. Similarly, plasma true triglycerides and free glycerol were not significantly different between groups (p = 0.148 and 0.529, respectively). Thiobarbituric acid reactive substances (TBARS) were also not significantly different between groups (p = 0.412).
Conclusion: The addition of the novel fiber-rich complex did not significantly affect high-fat diet-induced weight gain, adiposity, high blood sugar, lipid imbalance, or oxidative stress in this experimental design.
ContributorsLing, Jingyu (Author) / Sweazea, Karen (Thesis advisor) / Sears, Dorothy (Committee member) / Kim, Min-Hyun (Committee member) / Arizona State University (Publisher)
Created2024
Description
Studies show that having greater weight-for-length in infancy and obesity in childhood can lead to obesity in adolescence and adulthood. Reducing obesity risk factors may decrease one’s chance of developing obesity. This longitudinal observational study’s objective was to investigate longitudinal associations of infant nighttime sleep proportion with gut microbiome diversity and taxa abundance (n=30). Fecal samples, sleep diaries and sleep actigraphy were taken at 3 and 8 weeks, and 3, 6, 9, and 12 months during infancy. Diversity analysis was completed in Quantitative Insights Into Microbial Ecology 2 (QIIME 2.0) in conjunction with PERMANOVA tests for group comparisons. QIIME2 diversity plug-ins were used to calculate alpha diversity (Shannon index) and beta diversity (Unweighted UniFrac distance) metrics. Percent abundance values for bifidobacteria and lactobacillus were exported at the genus level for subsequent analyses. Mixed linear models (MLM) and Adonis multiple regression analyses were used to test for significant (alpha = 0.05) effects of nighttime sleep fraction on alpha and beta diversity metrics and abundance of specific microbial taxa. All statistical models accounted for individual effects (baby/subject ID), time, and a time*sleep fraction interaction. For aim 1, the regression model was: Shannon = baby + time + sleep fraction + time*sleep fraction. The overall regression was statistically significant (R2 = 0.518, F = 3.9576, p < 0.0001). Nighttime sleep proportion did not significantly predict gut microbiome richness in infants (β = 0.281, p = 0.8603). For aim 2, when adjusting for covariates in a multiple regression model, sleep fraction was insignificant. The R2= 0.005106, F= 0.810996, p=0.619). For aim 3, the fitted regression models were Bifidobacteria/Lactobacillus= baby + time + sleep fraction + time*sleep fraction. The overall regression for Bifidobacteria was statistically significant (R2 = 0.371944, F = 2.6286, p = 0.0008) but nighttime sleep proportion did not significantly predict Bifidobacteria abundance in infants (β = -54.40518, p = 0.2723). The overall regression for Lactobacillus was statistically significant (R2 = 0.236381, F = 1.8687, p = 0.0208) but sleep fraction was not associated with taxa abundance. Further research is needed to describe associations between sleep, gut microbiome, and the distal outcome of obesity.
ContributorsGross, Tav (Author) / Whisner, Corrie (Thesis advisor) / Sears, Dorothy (Committee member) / Petrov, Megan (Committee member) / Arizona State University (Publisher)
Created2024