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- All Subjects: Vegetarianism--Physiological aspects.
- Genre: Masters Thesis
- Creators: Johnston, Carol
- Creators: Cohen, Adam
- Creators: Wilkie, Lynn Melissa
- Member of: ASU Electronic Theses and Dissertations
Description
Dietary protein is known to increase postprandial thermogenesis more so than carbohydrates or fats, probably related to the fact that amino acids have no immediate form of storage in the body and can become toxic if not readily incorporated into body tissues or excreted. It is also well documented that subjects report greater satiety on high- versus low-protein diets and that subject compliance tends to be greater on high-protein diets, thus contributing to their popularity. What is not as well known is how a high-protein diet affects resting metabolic rate over time, and what is even less well known is if resting metabolic rate changes significantly when a person consuming an omnivorous diet suddenly adopts a vegetarian one. This pilot study sought to determine whether subjects adopting a vegetarian diet would report decreased satiety or demonstrate a decreased metabolic rate due to a change in protein intake and possible increase in carbohydrates. Further, this study sought to validate a new device called the SenseWear Armband (SWA) to determine if it might be sensitive enough to detect subtle changes in metabolic rate related to diet. Subjects were tested twice on all variables, at baseline and post-test. Independent and related samples tests revealed no significant differences between or within groups for any variable at any time point in the study. The SWA had a strong positive correlation to the Oxycon Mobile metabolic cart but due to a lack of change in metabolic rate, its sensitivity was undetermined. These data do not support the theory that adopting a vegetarian diet results in a long-term change in metabolic rate.
ContributorsMoore, Amy (Author) / Johnston, Carol (Thesis advisor) / Appel, Christy (Thesis advisor) / Gaesser, Glenn (Committee member) / Arizona State University (Publisher)
Created2012
Description
In 2002, a scientifically derived food guide pyramid for vegetarians, the Modified Food Guide for Lacto-ovo-vegetarians and Vegans was published and well received. Now that 10 years have passed, new scientific literature regarding the bioavailability of the nutrients of key concern in vegetarian diets has been published, and the graphical format of the nation's food guide has evolved from a pyramid shape into a circular plate. The objective of this research was to examine the post-2002 literature regarding the bioavailability of key nutrients in vegetarian diets; to use this information to update the recommendations made in the 2002 Modified Food Guide Pyramid for Lacto-ovo-vegetarians and Vegans; and to adapt this revised food plan to the new USDA MyPlate format. This process involved reviewing the scientific literature to determine if the DRIs for the nutrients of key concern in vegetarian diets are adequate for the vegetarian population and using this information to develop new recommendations for vegetarians if necessary, analyzing the nutrient content of representative foods in different food groups, reconfiguring the food groups so that foods with like nutrient components were grouped together, determining the number of servings of each food group required to meet vegetarians' nutrient requirements at three caloric levels, and developing sample menus. A circular plate graphic, the Vegetarian Plate, was designed to illustrate the recommendations of this updated food guide. This updated, scientifically derived food guide provides a sound base for diet planning for lacto-ovo-vegetarians and vegans. Further research is needed to assess the Vegetarian Plate's adequacy for children, pregnant and lactating women, athletes, and individuals with medical conditions or chronic diseases.
ContributorsFladell, Lauren (Author) / Johnston, Carol (Thesis advisor) / Vaughan, Linda (Committee member) / Shepard, Christina (Committee member) / Arizona State University (Publisher)
Created2013
Description
The unpleasant bitter taste found in many nutritious vegetables may deter people from consuming a healthy diet. We investigated individual differences in taste perception and whether these differences influence the effectiveness of bitterness masking. To test whether phenylthiocarbamide (PTC) `supertasters' also taste salt and sugar with greater intensity, as suggested by Bartoshuk and colleagues (2004), we infused strips of paper with salt water or sugar water. The bitterness rating of the PTC strip had a significant positive linear relationship with ratings of both the intensity of sweet and salt, but the effect sizes were very low, suggesting that the PTC strip does not give a complete picture of tasting ability. Next we investigated whether various seasonings could mask the bitter taste of vegetables and whether this varied with tasting ability. We found that sugar decreased bitterness and lemon decreased liking for vegetables of varying degrees of bitterness. The results did not differ by ability to taste any of the flavors. Therefore, even though there are remarkable individual differences in taste perception, sugar can be used to improve the initial palatability of vegetables and increase their acceptance and consumption.
ContributorsWilkie, Lynn Melissa (Author) / Phillips, Elizabeth D. (Thesis advisor) / Cohen, Adam (Committee member) / Johnston, Carol (Committee member) / Arizona State University (Publisher)
Created2012
Description
Epidemiological studies have identified obesity as a risk factor for numerous chronic diseases such as adult onset diabetes, hypertension, and hypercholesterolemia. In both humans and laboratory animals, high-fat diets have been shown to cause obesity. Increases in dietary fat lead to increased energy consumption and, consequently, significant increases in body fat content. CD36 has been implicated in fat perception, preference, and increased consumption, but it is yet to be tested using a behavior paradigm. To study the effect of CD36 on fat taste transmission and fat consumption, four CD36 knockout (experimental) mice and four Black 6 wildtype (control) mice underwent 20 days of fat preference and perception testing. Both groups of mice were exposed to foods with progressively increasing fat content (10%, 12.5%, 15% 17.5%, 20%, 45%) in order to assess the effect of CD36 on fat preference. Afterward, the mice were subjected to an aversive conditioning protocol designed to test the effect of CD36 on fat taste perception; development of a conditioned taste aversion was indicative of ability to taste fat. Especially, knockout mice exhibited diminished preference for and reduced consumption of fat during preference testing and were unable to identify fat taste as the conditioned stimulus during aversive conditioning. A repeated measures ANOVA with Bonferroni correction revealed a significant main effect of group on fat consumption, energy intake, and weight. Linear regression revealed CD36 status to account for a majority of observed variance in fat consumption across both phases of the experiment. These results implicate CD36 in fat taste perception and preference and add to the growing body of evidence suggesting fat as a primary taste.
ContributorsJasbi, Paniz (Author) / Johnston, Carol (Thesis advisor) / Lespron, Christy (Committee member) / Wadhera, Devina (Committee member) / Arizona State University (Publisher)
Created2018
Description
There is a considerable amount of research stating that vegetarian diets have an alkalizing effect while the typical western diet is acid-forming. There is substantial evidence regarding the health benefits of an alkaline diet. Although vegetarian diets demonstrate the ability to foster these health benefits, many people are still not willing to adopt a completely vegetarian diet. PURPOSE: To evaluate the effect of following a vegan diet two or three days per week on acid-base balance in a healthy college student population aged 18-30. METHODS: In a one-week interventional design, 23 people were randomly assigned to follow a vegan diet 2 days per week (VEG2;n=7), 3 days per week(VEG3;n=8), or 7 days per week (VEG7;n=8). Urine pH and dietary PRAL were assessed in each group at baseline and after the one-week intervention. RESULTS: There was no significant difference in urinary pH between the three groups (p=0.12). The change in PRAL values after the dietary intervention was different between the 3 groups (p=0.03). CONCLUSION: Adherence to a vegan diet 2 or 3 days per week did not show a significant change in urinary pH or PRAL.
ContributorsCosgrove, Kelly (Author) / Johnston, Carol (Thesis advisor) / Sweazea, Karen (Committee member) / Mayol-Kreiser, Sandra (Committee member) / Arizona State University (Publisher)
Created2015
Description
Background. Research suggests that non-O blood types are at an increased risk of thrombosis and related health complications in cardiovascular disease (CVD). This is due in part to higher concentrations of von Willebrand factor (VWF), an important factor involved in blood clotting. Objective. The purpose of this study was to examine the effects of a vegetarian-like diet on blood coagulation and other health parameters in adults with type A blood compared to type O blood over a four week intervention. Given the lack of previous research on blood type and diet, it was hypothesized that no difference in blood coagulation would be observed. Design. This study was a randomized, parallel arm, dietary intervention using healthy, omnivorous adults with blood types A and O. A total of 39 subjects completed the study. Subjects were randomized into two groups: a vegetarian-like diet group made up of 12 type As and 12 type Os and an omnivorous control diet group made up of 11 type As and 12 type Os. At weeks 0 and 4, fasting blood was drawn and analyzed for prothrombin time (PT), activated partial thromboplastin time (APTT), von Willebrand factor (VWF), total cholesterol, LDL, HDL, triglycerides, and CRP. In addition, subjects were weighed and filled out a FFQ at weeks 0 and 4. Results. After adhering to a vegetarian-like diet for four weeks, type Os had a significant increase in PT (+0.24±0.32 sec/ p=0.050), whereas type As saw no significant change. There was a trend of weight loss for type Os in the vegetarian-like diet group (-1.8±2.6 lb/ p=0.092) and significant weight loss for type As (-0.9±2.1 lb/ p=0.037). Both blood types O and A experienced significant decreases in BMI (-0.3±0.4/ p=0.092 and -0.2±0.3/ p=0.037, respectively). No change was seen in APTT, VWF, total cholesterol, LDL, HDL, triglycerides, or CRP. Conclusion. Type Os saw an increase in PT, perhaps indicating a reduction in risk of thrombosis and its related health complications. Type As were less responsive to the dietary intervention and may require more rigid dietary guidelines or a longer time on such a diet to see the benefits.
ContributorsBrown, Jennifer (Author) / Johnston, Carol (Thesis advisor) / Martin, Keith (Committee member) / Shepard, Christina (Committee member) / Arizona State University (Publisher)
Created2013