Dietary GIycaemic Index, Glycaemic Load and insulin resistance (HOMAIR) of healthy South Asians in Glasgow, UK

George, Ramlah (2015) Dietary GIycaemic Index, Glycaemic Load and insulin resistance (HOMAIR) of healthy South Asians in Glasgow, UK. PhD thesis, University of Glasgow.

Abstract

High habitual dietary glycaemic index (GI) and glycaemic load (GL) may relate to elevated insulin resistance and therefore may be more important and relevant in South Asian populations known for high prevalence of insulin resistance. The main objective of this research was to investigate the dietary GI, GL and insulin resistance of a sample of healthy South Asians in Glasgow, UK (a total of 111 healthy individuals: 60 males, 30 South Asians and 30 Europeans; 51 females, 22 South Asians and 29 Europeans). Estimation of dietary GI and GL (from weighed food intake records) considered the GI values of single foods and mixed-meals from relevant publications and from laboratory food/mixed-meal GI measurements (Chapter 3). The GI of key staple South Asian foods alone (chapatti, rice, pilau rice) and as mixed meals with curried chicken was measured using standard methods on 13 healthy subjects. The key staples had medium GI (chapatti, 68; rice, 66 and pilau rice, 60) and glycaemic responses to the mixed-meal of staples with curried chicken were found to be lower than the staples eaten alone. GI of the mixed-meals fell in the low GI category (chapatti with curried chicken, 45 and pilau rice with curried chicken, 41). Weighed food intake records (WFR) (recorded for 3-7 days) and self-administered previously validated food frequency questionnaires (FFQ) (applied to habitual food intakes in the past 6 months) was assessed for agreement through correlation analyses, cross-classification analysis, weighted Kappa statistics and Bland and Altman statistics. The two methods mostly agreed in carbohydrate (CHO) food intakes implying that the WFR reflected habitual intakes (Chapter 4). In consideration of potential confounding effect of physical activity on the relationship between dietary variables and HOMAIR, physical activity level (PAL) and Metabolic equivalent score (METS) of main daily activities of study subjects were derived from self-reported physical activity records (Chapter 5). Mean PAL were similar between South Asian and European males (median PAL of 1.61 and 1.60, respectively) but South Asian females tended to be less physically active than European females (mean PAL of 1.57 and 1.66, respectively). South Asians were less physically active in structured exercise and sports activities, particularly South Asian females and South Asians (males and females combined) with reported family history of diabetes showed inverse relationship between daily energy expenditure and HOMAIR. South Asians were found to be more insulin resistant than Europeans (HOMAIR median (IQR) of 1.06 (0.58) and 0.91 (0.47), p-value= 0.024 respectively in males; mean (SD) of 1.57 (0.80) and 1.16 (0.58), p-value= 0.037, respectively in females) despite similarities in habitual diet including dietary GI and GL. The mean habitual dietary GI of South Asians was within the medium GI category and did not differ significantly from Europeans. South Asian and European males’ dietary GI (mean, SD) was: 56.20, 2.78 and 54.77, 3.53 respectively; p-value=0.086. South Asian and European females also did not differ in their dietary GI (median, IQR) was: 54, 4.25 and 54, 5.00; p-value=0.071). Top three staples ranked from highest to lowest intakes in the South Asian diet were: unleavened breads (chapatti, Naan/Pitta, Paratha), rice, bread (white, wholemeal, brown), and potatoes. After statistically controlling for energy intake, body mass index, age, physical activity level and socio-demographic status, an inverse relationship (Spearman partial correlation analyses) between dietary GI and HOMAIR was observed (r, -0.435; p-value, 0.030) in South Asian males. This may be explained by the observation that the lower the dietary GI, the lower also, the total carbohydrates and fibre intakes and the higher the fat intake. In South Asian females, dietary GI and GL respectively, did not relate to HOMAIR but sugars intake related positively with HOMAIR (r, 0.486; p-value, 0.048). South Asian females, compared to European females, reported higher intakes of dietary fat (38.5% and 34.2% energy from fat, respectively; p-value=0.035). Saturated fatty acid (SFA) intakes did not differ between ethnic groups but SFA intakes were above the recommended level of 10% of total dietary energy for the UK in all groups, the highest being in SA females. In conclusion, Ethnicity (South Asian), having family history of diabetes, the wider diet profile rather than habitual dietary glycaemic index and glycaemic load alone (low GI, low fibre and high fat diets in males for instance; and high fat, high sugar diets in females) as well as low physical activity particularly in structured exercise and sports may contribute to insulin resistance in South Asians. These observations should be confirmed in larger future studies.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Chapter 3 of this thesis has been published: George R., Garcia A.L. and Edwards C.A. (2014) Glycaemic responses of staple South Asian foods alone and combined with curried chicken as a mixed meal. J Hum Nutr Diet. doi: 10.1111/jhn.12232
• Keywords: dietary glycaemic index, dietary glycaemic load, blood glucose, insulin resistance, HOMA-IR, healthy South Asians.
• Subjects: R Medicine > R Medicine (General); R Medicine > RA Public aspects of medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
• Supervisor's Name: Edwards, Professor Christine A.
• Date of Award: 2015
• Depositing User: Ms Ramlah George
• Unique ID: glathesis:2015-6600
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 18 Aug 2015 08:16
• Last Modified: 11 Aug 2016 11:00
• URI: https://theses.gla.ac.uk/id/eprint/6600