The ethnicity enigma: Unravelling the dietary, metabolic and physiological differences

• Main Author: Verena, Tan Ming Hui
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01.01.2015
• Subjects: Health care management
• ISBN: 9781369480368; 1369480369

Background Within the Asian population, there are ethnic differences in susceptibility to and prevalence of obesity and Type 2 Diabetes Mellitus (T2DM). We aimed to understand the dietary habits of individuals with T2DM in Singapore, examine ethnic differences in glucose homeostasis, glycemic response and insulin kinetics, as well as physiological digestive factors amongst the ethnic groups to provide insights into the varying susceptibilities to T2DM. Objectives 1. To examine the dietary habits (carbohydrate sources and dietary GI) of individuals with T2DM in Singapore. 2. To study beta-cell function in relation to insulin sensitivity and understand glucose homeostasis amongst the ethnic groups. 3. To measure physiological factors involved in digestion amongst the ethnic groups. Methods 1. Three hundred and six participants (99 Chinese, 96 Malays, and 111 Asian- Indians) were recruited. Blood samples, anthropometric and clinical ix measurements, and two 24-hour dietary recalls were obtained. Nutrient intake, dietary glycemic index (GI) and glycemic load (GL) were computed. 2. Fifty nine normoglycemic lean males (14 Chinese, 21 Malay and 24 Asian- Indians) underwent a euglycemic-hyperinsulinemic clamp procedure and a liquid mixed meal tolerance test (LMMTT). Insulin sensitivity, beta-cell function, postprandial glucose and insulin responses were determined. 3. Seventy five healthy males (25 Chinese, 25 Malay, and 25 Asian-Indians) were recruited. Subjects were served glucose reference, Jasmine rice (JR) and Basmati rice (BR) on separate occasions. Postprandial blood glucose and plasma insulin concentrations were measured over 180 min. Mastication parameters, saliva α-amylase activity, AMY1 gene copy numbers and gastric emptying rate were also determined to investigate their relationships with glycemic response. Results 1. The Malays had both poorer metabolic (higher BMI, poorer lipids profile) and dietary profiles (high GL, GI, intake of saturated fat and sugars) compared to Asian-Indians and Chinese. 2. Asian-Indians were the least insulin sensitive among the ethnic groups. The glycemic response during LMMTT was significantly greater in Malays compared to Asian-Indians and Chinese. However, there were no significant differences in insulin response between ethnic groups. The oral disposition index, a measure of beta-cell function relative to insulin sensitivity during the LMMTT, was the lowest in Malays, followed by Asian-Indians and Chinese. 3. The GI and Insulinemic Index (II) of JR and BR did not differ significantly between ethnicities. We found no effect of ethnicity, salivary α-amylase activity, particle size distribution, gastric emptying rate and AMY1 gene copy numbers on glycemic response (GR). Mastication parameters such as the number of chews at each mouthful and the chewing time per mouthful showed a significant relationship with GR. Conclusion We found ethnic differences in the diet of individuals with T2DM in terms of the quantity and quality of the carbohydrates consumed. The understanding of such dietary differences can aid ethnic-specific nutrition recommendations to achieve better glycemic control and metabolic profile. Through understanding glucose homeostasis and insulin kinetics among the ethnic groups, we demonstrated that the pathways leading to T2DM might differ between Malay and Asian-Indians. In the final study, we showed that digestive function such as mastication rate, salivary α-amylase activity and gastric emptying rate modulates carbohydrate metabolism and influenced the glycemic response.