Barley has been receiving increased attention as a human food due to the health benefits associated with β-glucan fiber and its potential as a low glycemic index (GI) functional food. Research has shown a relationship between the physico-chemical properties of β-glucan and the physiological effects, which may be altered by processing. However, it is not known if the physiological effects of consuming barley are affected by variations in chemical composition among cultivars or by common processing methods such as pearling or milling. The primary objective of this thesis was to characterize the effects of differences in cultivar starch and fibre content, level of pearling and milling on the GI, satiety and the physico-chemical properties of β-glucan. Nine barley cultivars varying in starch-type and β-glucan content were studied in three experiments in separate groups of ten healthy participants. Blood glucose and satiety ratings were measured and the GI was calculated. Total starch, total fibre, β-glucan, molecular weight (MW), solubility and β-glucan viscosity were determined in vitro. Results showed that GI varied by cultivar (CDC-Fibar, 26 ± 3 vs. AC-Parkhill, 35 ± 4, P < 0.05) and pearling (WG, 26 ± 4 vs. WP 35 ± 3, P < 0.05). When two cultivars were milled and processed to wet pasta the GI increased by 184% (P < 0.05). The pearled wet pasta had a significantly lower GI compared to the whole grain (P < 0.05). Boiled barley kernels tended to elicit greater satiety than white bread, but the difference was not significant. In both the boiled barley kernels and the wet pasta, pearling did not affect the MW, viscosity and solubility. MW did not significantly differ between cultivars but solubility and viscosity did (P < 0.05). The wet pasta had significantly lower MW, solubility, viscosity but not β-glucan content than the boiled barley kernels (P < 0.05). In conclusion, pearling did not have an effect but milling and extruding resulted in significant reduction in MW, solubility and viscosity. The GI of barley is influenced significantly by cultivar, pearling and milling. Further studies are required to determine the effect on satiety.

As part of a project to see whether potatoes with a low glycemic-index (GI) could be developed through plant breeding, the GI values of 4 new potato varieties differing in starch structure was determined in 3 studies over 2 years in human subjects. Since cooking and cooling affects starch structure the potatoes were studied both freshly cooked (boiled) and cooled. The first study showed that cooling reduced the GI of two varieties by 40-50% but had no effect in the others (treatment × variety interaction, p=0.024), an effect which was confirmed in study 2. Differences in GI were readily explained by differences in starch structure or in-vitro digestion rate. Carbohydrate malabsorption increased from 3 to 5% upon cooling, not enough to account for the reduced GI. It is concluded that the effect on GI of cooling cooked potatoes varies in different varieties. Further research is needed to understand the mechanism.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 90-99)

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 132-151).

Please read the abstract in the dissertation / Dissertation (M (Dietetics))--University of Pretoria, 2008. / Human Nutrition / M (Dietetics) / unrestricted

Carbohydrates and fats are the main fuel sources for energy production during exercise. Consumption of low glycemic index foods slows digestion and absorption in the small intestine. The slow digestibility of resistant starch containing foods contributes to the slow and sustained release of glucose into the bloodstream, minimizing occurrence of hyperinsulinemia-induced suppression of lipolysis. The objectives of this study were to determine the consumption of resistant starch (RS) by regular exercisers (Blacksburg and San Jose (SJ)); and to analyze the eating and exercise habits of the subjects. Subjects were recruited at gyms in SJ (n=27) and Blacksburg (n=26). Participants kept 3-day food records and completed a questionnaire on eating habits and physical activity. Mean body mass index for the subjects was similar (SJ: 23.06 Kg/m² ± 2.55; Blacksburg: 23.53 Kg/m² ± 3.09). Average exercise time was 12 hours/week, and > 50% engaged in weight training in addition to aerobic type exercise. Percentage contribution of carbohydrates to the total energy intake was significantly higher for SJ males (53.53% ± 8.06%) compared to Blacksburg males (48.39% ± 6.33%; alpha=0.10). Prominent RS food sources in both groups were pasta, potatoes, bananas, and corn. Rice and various legumes were more frequent in the SJ group. It appears that consumption of RS is higher among SJ subjects. Consumption of RS prior to prolonged exercise could cause stable glycemic and insulinemic responses that may help delay the onset of fatigue during exercise. / Master of Science

Master of Science / Food Science / Fadi Aramouni / Little in vivo research on glycemic index (GI) values or the digestive impact of sorghum based food products currently exists. Because sorghum is a gluten-free grain, its utilization in the United States is growing, especially in baking applications. Information on how sorghum affects blood sugar levels would be beneficial as new products emerge because glycemic effect has an impact on human health and in controlling diabetes. The objective of this study was to determine the GI of a sorghum muffin, and compare this value to the GI of muffins made from commonly consumed grains in the United States. The effects of particle size and damaged starch on GI were also studied. GI values were determined for muffins made from white sorghum, corn, brown rice, whole wheat, and all-purpose flours. All muffin formulations were composed of flour, water, baking powder and salt. To determine the GI, weighed portions of muffin containing 20g of available carbohydrates were eaten on separate occasions by eight healthy volunteers (ages 18-40) after an overnight fast (10 hours). Each muffin was administered twice. Two capillary blood samples were taken at 0 (fasting), 30, 45, 60, 90 and 120 minutes after consumption and averaged. Blood glucose curves were constructed from mean blood glucose values. The GI was calculated by dividing the incremental area under the curve for the test food (muffin) by that for the standard (20g dextrose drink) and multiplying by 100. The GI for the muffins was calculated as the mean from the respective average GIs of the 8 volunteers. The data indicated that sorghum flour milled at particle size < 400 um resulted in the lowest GI of 32 ± 16.8. These findings should assist in development of lower GI sorghum foods.

[Truncated abstract] Type 1 Diabetes is emerging as a significant public health problem faced by nearly every country in the world. It has major economic and social implications with considerable burden of illness. Approximately 140,000 Australians have been diagnosed with T1DM with an annual increase in incidence rate of 3% per year, comparable to the overall global increase. The management of T1DM requires insulin therapy which places considerable burden on the patient and their carers. Coping with daily insulin injections, dietary changes, modification of physical activity and vigilant monitoring of blood glucose levels, will impact on patient?s quality of life. The optimum goal for the treatment of type 1 diabetes is to safely achieve near-normal glycaemia and failure to maintain this goal accelerates the progression of the devastating long term complications of diabetes. Unfortunately attempts to achieve near normal glycaemia are limited by the risk of excessive lowering of blood glucose levels and hypoglycaemia remains a major barrier to strict glucose control of diabetes. In general this thesis focuses on two fundamental issues related to the epidemiology of severe hypoglycaemia. Namely, methodological consideration when analysing prospective observational data and application of the most robust methodology. A prospective open cohort study of the Princess Margaret Hospital diabetes clinic established in 1992, with 99% case ascertainment was used. This hospital is the only paediatric referral centre for type 1 diabetes and every child diagnosed in the state of Western Australia is treated at this centre. ... The results of this study showed that severe hypoglycaemia remains a major problem and recent approaches to therapy may be allowing a degree of improved control without the expected increased risk of severe hypoglycaemia. The study in chapter 7 investigates genetic risk factors related to severe hypoglycaemia. A significant relationship where the presence of the iv deletion (D) allele of the angiotensin-converting enzyme (ACE) increases risk of severe hypoglycaemia has been reported. This study concludes that the presence of D allele of the ACE gene does not predict a significantly higher risk of severe hypoglycaemia. In an attempt to optimize glycemic control, patients may suffer multiple episodes of severe hypoglycaemia which can adversely affect quality of life as well as educational and intellectual disadvantage. The study in chapter 8 investigates the factors related to recurrent severe hypoglycaemia. A rigorous and informative time-to-event approach is used to account for within child correlation, staggered enrolment and timevarying covariates. This allows important risk factors to change over time. Preschool children have an increased risk of experiencing recurrent severe hypoglycaemia. The findings of this thesis highlights the importance of selecting appropriate analytical methodology to identify risk factors associated with severe hypoglycaemia and also to dismiss factors that had previously been thought to be important. This will help in formulating management plans in order to limit the impact of severe hypoglycaemia.

Research investigating the effects of pre-exercise meals with varying glycemic indices on exercise performance in intermittent sports is scarce. This study determined whether whole foods of low glycemic index (GI) resulted in a metabolic and performance advantage, in comparison to high GI foods, when eaten prior to extended intermittent cardiovascular exercise, such as tournament soccer play. Consenting trained participants (10 males, 4 females, 25.8 ± 7.3 y) completed two simulated soccer tournaments separated by at least seven days. Each testing day included two 90-minute soccer matches separated by a three hour break. Using a randomized cross-over design, low-GI, lentil-based meals (GI~42) or high-GI, potato-based meals (GI~78) matched for caloric value were consumed two hours prior to and then within one hour after the first soccer match. Blood glucose, lactate, insulin, free fatty acids, and respiratory gases were measured throughout the post-prandial and testing periods. Ratings of perceived exertion (RPE) and gastrointestinal symptoms were also recorded. Performance was measured by the distance covered during five one-minute sprints, separated by two minute and thirty second rest intervals, at the end of each match. Peak post-prandial blood glucose was higher (p<0.05) in the high-GI trial (8.9 ± 2.2 molL-1 [SD]) compared to the low GI trial (5.9 ± 1.3 mmolL-1) as was insulin prior to the start of exercise (19.4 ± 2.0 versus 9.2 ¬± 1.3 umolL-1, p<0.05). Blood lactate levels were significantly higher (p<0.05) at the end of the second match during the high-GI trial (6.1 ± 1.2 mmolL-1) compared to the low-GI trial (2.5 ± 0.4 mmolL-1). Breath-by-breath analysis showed lower (p<0.05) carbohydrate oxidation during the low-GI trials compared to the high-GI at the start of the first soccer match (p<0.05). Subjects reported greater feelings of hunger during the high-GI trial versus greater feelings of fullness during the low-GI trial (p<0.05), but RPE during the low-GI (14.1 ± 0.3) was similar to the high-GI meal (14.2 ± 0.3). Sprint distance was not significantly different between treatments (p=0.27). Overall, these findings suggest that lentil-based, low-GI foods are a comparable alternative to traditional high-GI pre-exercise meals, as they result in similar performance outcomes but improved metabolic profiles. Over the long-term, improving metabolic conditions during exercise may be beneficial to the health of athletes.

Research investigating the effects of pre-exercise meals with varying glycemic indices on exercise performance in intermittent sports is scarce. This study determined whether whole foods of low glycemic index (GI) resulted in a metabolic and performance advantage, in comparison to high GI foods, when eaten prior to extended intermittent cardiovascular exercise, such as tournament soccer play. Consenting trained participants (10 males, 4 females, 25.8 ± 7.3 y) completed two simulated soccer tournaments separated by at least seven days. Each testing day included two 90-minute soccer matches separated by a three hour break. Using a randomized cross-over design, low-GI, lentil-based meals (GI~42) or high-GI, potato-based meals (GI~78) matched for caloric value were consumed two hours prior to and then within one hour after the first soccer match. Blood glucose, lactate, insulin, free fatty acids, and respiratory gases were measured throughout the post-prandial and testing periods. Ratings of perceived exertion (RPE) and gastrointestinal symptoms were also recorded. Performance was measured by the distance covered during five one-minute sprints, separated by two minute and thirty second rest intervals, at the end of each match. Peak post-prandial blood glucose was higher (p<0.05) in the high-GI trial (8.9 ± 2.2 molL-1 [SD]) compared to the low GI trial (5.9 ± 1.3 mmolL-1) as was insulin prior to the start of exercise (19.4 ± 2.0 versus 9.2 ¬± 1.3 umolL-1, p<0.05). Blood lactate levels were significantly higher (p<0.05) at the end of the second match during the high-GI trial (6.1 ± 1.2 mmolL-1) compared to the low-GI trial (2.5 ± 0.4 mmolL-1). Breath-by-breath analysis showed lower (p<0.05) carbohydrate oxidation during the low-GI trials compared to the high-GI at the start of the first soccer match (p<0.05). Subjects reported greater feelings of hunger during the high-GI trial versus greater feelings of fullness during the low-GI trial (p<0.05), but RPE during the low-GI (14.1 ± 0.3) was similar to the high-GI meal (14.2 ± 0.3). Sprint distance was not significantly different between treatments (p=0.27). Overall, these findings suggest that lentil-based, low-GI foods are a comparable alternative to traditional high-GI pre-exercise meals, as they result in similar performance outcomes but improved metabolic profiles. Over the long-term, improving metabolic conditions during exercise may be beneficial to the health of athletes.