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- Genre: Academic theses
- Creators: Johnston, Carol
- Status: Published
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
Vegetarian diets can provide an abundance of nutrients when planned with care. However, research suggests that vegetarian diets may have lower protein quality than omnivore diets. Current protein recommendations assume that vegetarians obtain a majority of their protein from animal products, like dairy and eggs. Studies have shown that this assumption may not be valid. The recommended dietary allowance (RDA) may not be adequate in vegetarian populations with high protein requirements. The purpose of this study is to analyze dietary protein quality using the DIAAS (Digestible Indispensable Amino Acid Score) method in both vegetarian and omnivore endurance athletes. 38 omnivores and 22 vegetarians submitted 7-day food records which were assessed using nutrition analysis software (Food Processor, ESHA Research, Salem, OR, USA). Dietary intake data was used to calculate DIAAS and determine the amount of available dietary protein in subject diets. Dietary data was compared with the subjects’ lean body mass (obtained using DEXA scan technology), and strength (quantified using peak torque of leg extension and flexion using an isokinetic dynamometer). Statistical analyses revealed significantly higher available protein intake in the omnivore athletes (p<.001). There were significant correlations between available protein intake and strength (p=.016) and available protein intake and lean body mass (p<.001). Omnivore subjects had higher lean body mass than vegetarian subjects (p=.011). These results suggest that vegetarian athletes may benefit from higher overall protein intakes to make up for lower dietary protein quality.
ContributorsZuelke, Corinne (Author) / Johnston, Carol (Thesis advisor) / Wharton, Christopher (Christopher Mack), 1977- (Committee member) / Dixon, Kathleen (Committee member) / Arizona State University (Publisher)
Created2017
Description
Background: The Academy of Nutrition and Dietetics states that it is possible for a vegetarian to obtain the recommended amount of nutrients with a properly planned diet but nutrient deficiencies, such as vitamin B12 deficiency, may occur if diet planning is not optimal. An early indicator of B12 deficiency is raised homocysteine concentrations in blood which can cause health issues.
Objective: The amino acid methionine is consumed via dietary protein. Methionine is used in the biosynthesis of other proteins. After a removal of a methyl group, it makes homocysteine. Slightly raised homocysteine may promote greater synthesis of glutathione, an important endogenous antioxidant protectant. It can then be recycled back into methionine or converted into cysteine with the addition of various B-vitamins such as vitamin B12, folic acid, and vitamin B6. Cysteine then uses outside sources of glutamate and glycine to create glutathione (GSH). With the catalyst glutathione peroxidase it donates an electron and becomes the oxidized form, glutathione disulfide (GSSG). It can then convert back to GSH with the aid of glutathione reductase by using the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as an electron donor. This study will examine glutathione levels in omnivores and vegetarians and see if it is related to vitamin B12 and homocysteine levels.
Design: This cross-sectional study encompassed 16 omnivores and 17 vegetarians from Phoenix, Arizona. A vegetarian diet was defined as one that excludes red meat, poultry, pork and seafood but allows dairy products and/or eggs; the diet had to be followed for at least one year. An omnivore diet is defined as eats meat daily. Participants completed a diet questionnaire and a vitamin B12, B6 and folate food questionnaire and provided a fasting blood sample.
Results: The mean plasma B12 and homocysteine did not differ between diet groups. Glutathione was significantly lower among vegetarians in comparison to omnivores, 1.9±0.5 and 2.3±0.7 mmol respectively (p=0.046).
Conclusions: The hypothesis was shown to be incorrect that vegetarians would have a higher glutathione level than omnivores as a result of their modest consumption of vitamin B12. The implications of a reduced glutathione status are discussed.
Objective: The amino acid methionine is consumed via dietary protein. Methionine is used in the biosynthesis of other proteins. After a removal of a methyl group, it makes homocysteine. Slightly raised homocysteine may promote greater synthesis of glutathione, an important endogenous antioxidant protectant. It can then be recycled back into methionine or converted into cysteine with the addition of various B-vitamins such as vitamin B12, folic acid, and vitamin B6. Cysteine then uses outside sources of glutamate and glycine to create glutathione (GSH). With the catalyst glutathione peroxidase it donates an electron and becomes the oxidized form, glutathione disulfide (GSSG). It can then convert back to GSH with the aid of glutathione reductase by using the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as an electron donor. This study will examine glutathione levels in omnivores and vegetarians and see if it is related to vitamin B12 and homocysteine levels.
Design: This cross-sectional study encompassed 16 omnivores and 17 vegetarians from Phoenix, Arizona. A vegetarian diet was defined as one that excludes red meat, poultry, pork and seafood but allows dairy products and/or eggs; the diet had to be followed for at least one year. An omnivore diet is defined as eats meat daily. Participants completed a diet questionnaire and a vitamin B12, B6 and folate food questionnaire and provided a fasting blood sample.
Results: The mean plasma B12 and homocysteine did not differ between diet groups. Glutathione was significantly lower among vegetarians in comparison to omnivores, 1.9±0.5 and 2.3±0.7 mmol respectively (p=0.046).
Conclusions: The hypothesis was shown to be incorrect that vegetarians would have a higher glutathione level than omnivores as a result of their modest consumption of vitamin B12. The implications of a reduced glutathione status are discussed.
ContributorsManley, Rachel Christine (Author) / Johnston, Carol (Thesis advisor) / Levinson, Simin (Committee member) / Barth, Christina (Committee member) / Arizona State University (Publisher)
Created2019
Description
Vitamin B12, found only in animal products, is a water-soluble vitamin important for DNA methylation, purine and pyrimidine synthesis, and the myelination of nerves. Symptoms of vitamin B12 deficiency include anemia, gait disturbances, altered vibration proprioception, impaired vision, psychosis, depression, dementia-like illness, and ultimately death. Because vegetarians and vegans consume fewer animal products in their diet than omnivores, they are inherently more at risk for developing these symptoms of vitamin B12 deficiency. Thus, the purpose of this study is to examine the correlation between nervous system markers (balance, dexterity, and vibration sensitivity) and markers of vitamin B12 nutriture (serum B12 and serum holo-transcobalamin II) in a cross-sectional study (n=38). In addition, the impact of daily oral vitamin B12 supplementation on these markers in an 8-week randomized controlled trial was also examined (n=18). The results of the cross-sectional study revealed a moderate correlation (R=-0.351, p=0.031) between serum B12 and left-hand functional dexterity. The results of the intervention study revealed no significant time*group interactions for markers of nervous system functions and biochemical values (after the removal of outliers). In addition, the time*group interaction appeared to be larger for those individuals with a baseline serum B12 of less than 303 pmol/L. These results suggest that vitamin B12 supplementation may have a more pronounced effect on those individuals who are in a state of vitamin B12 depletion (<303 pmol/L serum concentration). In addition, the results also suggest that 8 weeks of oral supplementation is not a long enough period to create significant clinical change, and it is likely that improvements in neurological measures would require long-term supplementation.
ContributorsArnold, Taylor (Author) / Johnston, Carol (Thesis advisor) / Whisner, Corrie (Committee member) / Ohri-Vachaspati, Punam (Committee member) / Lee, Chong (Committee member) / Aleck, Kyrieckos (Committee member) / Arizona State University (Publisher)
Created2016