Includes bibliographical references (leaves 196-220) Studies the growth, body composition, feed intake of grazing animals, the use of anabolic agents, fatty acid composition of ruminants fats; and, the effect of saturated fat on human health.

Whole fruits, grains and vegetables contain thousands of potential disease-fighting, healthpromoting nutrients. These foods play a critical role in bowel function, especially in the elderly. Strong epidemiological evidence has shown that greater amounts of crude dietary fibre are associated with a lesser prevalence of constipation and other gastrointestinal disorders. Constipation usually presents as a variety of symptoms, including reduced frequency of defaecation and impacted forms of stools and/or increased effort required to defaecate. Constipation is a problem that could affect any person at any time in his or her life, but in the elderly is more prevalent.Although anecdotal reports and dietary advice have suggested the use of kiwifruit as a laxative in humans, there are, at present no data available to support this. Kiwifruit is reported as the most nutrient-rich of the top 27 fruits eaten in the world today. The laxative property of kiwifruit could provide a natural remedy for constipation and would be cheaper than the laxatives on the market.Objective: The main objective of this study was to investigate if kiwifruit can act as a laxative, especially in elderly people.Study Design and Methods: This study was carried out in two stages, as a pilot and then a main study. In the pilot study, 71 participants (aged 18 - 50y) were divided into Group I and Group II. Group I made no changes to their normal diet for a six weeks period, while Group II were asked to add one kiwifruit for every 30kg body weight per day to their diet for a six week period. After the six weeks, the two experimental groups crossed over, maintaining the dietary regime followed by the other group for a further six weeks. So each subject was his or her own control. Daily recording of the frequency and characteristics of the stool were made by the participants in a diary. In the main study, 42 participants (aged 60 years and over) carried out the same dietary regime as the pilot study subjects. Elderly subjects of Group I made no changes to their diet, but was asked to record their daily frequency and characteristics of their stool for 3weeks. Group II subjects ate one kiwifruit for every 30kg body weight per day for a period of 3weeks. After the three weeks period, the two groups crossed over.Results: It was found from the pilot study that kiwifruit consumption was associated with significant softening of the stool (P<0.001); a significant increase in bulking of the stool (P=0.034) and the ease of bowel movement was improved (P<0.001). For the main study, kiwifruit consumption also showed softening of the stool (P<0.001) and the ease of bowel movement was improved (P<0.001), there was a slight but significant increase in bowel frequency (P=0.012) and the bulking of stool (P=0.002).Conclusion: The results from this study provide evidence that consumption of kiwifruit enhances laxation and that bowel function can be improved through changes in diet, both for younger and elderly people.

There is much interest in the nature and quality of the diet consumed by adolescents. To determine whether there are significant associations between diet and gain in height and weight in this age group, the present study analysed data on food intake and weight and height obtained on three occasions over a 30-month period from a total of 326 adolescents aged between 12 and 15 years. Information on sociodemographic and other lifestyle factors, including an indicator of physical activity, was also obtained. Energy intake was found to be a significant positive predictor of both height and weight gain. In addition intake of fat, calcium and riboflavin were found to be significant positive predicators of height gain and intake of carbohydrate and starch significant positive predictors of weight gain. After controlling for energy intake only riboflavin approached significance as a positive predictor of height gain. A food group analysis identified intake of dairy foods as a significant predictor of height gain. Although statistically significant the dietary predictors explained only a small proportion of the variability in height and weight (≤3.5%). Given the difficulties in obtaining complete dietary records from this age group and the generally adequate nature of the diet in the study group, the small proportion of height and weight gain explained by diet is not unexpected. Nevertheless the nutrient predictors identified are consistent with nutrient requirements for growth during adolescence and highlight the importance, for this age group, of an adequate intake of nutrients specifically provided by dairy foods. Few significant associations were found between growth rates and the sociodemographic and the lifestyle factors measured in this study. The ethnic diversity of the study sample may have contributed to this outcome.

The research presented in this thesis relates to the gastrointestinal control of appetite and some of the consequences of nutritional frailty, namely postprandial hypotension and vitamin D insufficiency. Undernutrition and its consequences are increasingly common problems in an ageing population, and improved management is dependent on an understanding of the factors which are involved in the control of appetite, and the physiological decline of appetite with increasing age termed ‘the anorexia of ageing’. The role of the gastrointestinal hormone ghrelin was specifically evaluated, in relation to the effects of age and nutrient digestion on circulating ghrelin concentrations (Chapters 6 and 7). The effect of fat digestion on the postprandial blood pressure response in healthy older subjects was evaluated in the study reported in Chapter 8. In addition, the results of some intervention studies are described in Chapters 9 and 10, the former study relating to nutritional supplementation as a strategy to increase energy intake, and the latter study to the effects of vitamin D replacement therapy on glucose and insulin metabolism. Whilst plasma ghrelin concentrations are less in older than young rodents, the consequences of healthy ageing on circulating plasma ghrelin concentrations in humans are unclear. The variations in fasting ghrelin concentrations over a sixty year age range were evaluated in healthy young and older subjects (Chapter 6). Plasma ghrelin concentrations were higher in females than males, but did not correlate with age, and were inversely related to body mass index. Ghrelin was independently, and inversely, related to total body skeletal muscle mass, but not to any other body composition variable. Strategies for increasing muscle mass, through resistance exercises, may, accordingly, aid in abolishing the compensatory rise in ghrelin concentrations seen with undernutrition and weight loss. Plasma ghrelin concentrations increase before, and decrease to trough levels within one hour of ingestion of a meal. Macronutrients differ in their ability to suppress ghrelin, being earlier and more pronounced after carbohydrate, and relatively delayed after fat or protein, ingestion. The role of carbohydrate and fat digestion in the suppression of plasma ghrelin concentrations was investigated in healthy young adults (Chapter 7). The suppression of ghrelin concentrations following a sucrose drink was attenuated by acarbose, which slows small intestinal carbohydrate absorption. Ghrelin concentrations were also suppressed after consumption of a fat-enriched drink, however addition of orlistat, which reduces fat digestion and absorption, attenuated the fall in plasma ghrelin. Thus, nutrient digestion is required, in addition to exposure of the small intestine to nutrients, for suppression of ghrelin. Postprandial hypotension describes a significant fall in blood pressure occurring up to two hours after a meal. The magnitude of the fall in postprandial blood pressure depends, in part, on the macronutrient composition of a meal, and the effects are particularly discernable in older adults. Although carbohydrates are particularly potent in reducing postprandial blood pressure in older adults, fat ingestion appears to have comparable, but delayed effects. The role of fat digestion in modifying the blood pressure responses was evaluated in healthy older adults (Chapter 8). There was a fall in blood pressure after ingestion of a high-fat drink. Orlistat, a lipase inhibitor which reduces intestinal fat absorption, potentiated the fall in postprandial blood pressure after a fat-enriched drink. Gastrointestinal function and appetite can be modulated by dietary manipulation of the macronutrient composition of an individual’s diet. The intervention study described in Chapter 9 evaluated the effects of two weeks of dietary fat supplementation on the sensitivity to the satiating effects of intravenous cholecystokinin-8 in healthy older subjects. No differences were observed in fasting, or postprandial plasma cholecystokinin concentrations after the dietary supplementation period compared to regular diet. There were also no differences in spontaneous energy intake at a buffet meal in response to exogenously administered cholecystokinin between the two diet periods. Vitamin D deficiency is common, as is type 2 diabetes, and the two conditions may be linked. There is mounting evidence linking vitamin D deficiency with abnormalities of glucose and insulin metabolism. The effects of vitamin D therapy in healthy young and older adults with low vitamin D concentrations in the setting of normal or impaired glucose tolerance were evaluated (Chapter 10). Vitamin D therapy, which normalised serum 25-hydroxyvitamin D concentrations in these individuals, did not alter glucose or insulin concentrations or insulin sensitivity during an oral glucose tolerance test. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339020 / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

"June 2004" / Includes bibliographical references. / 1 v. : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004

Graduation date: 1992

Thesis (M.S.)--Eastern Illinois University, 2004. / Includes bibliographical references (leaves 49-54).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / "Fmet" after tRNA in title is superscript. Vita. Includes bibliographical references (leaves 102-119). Available also in a digital version from Dissertation Abstracts.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 105-117).

published_or_final_version / Botany / Master / Master of Philosophy