Diet & insulin resistance: a review & Asian Indian perspective

Insulin resistance is associated with type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD). These abnormalities have been aggravated because of imbalanced and excess nutrition in developed countries, and rapid nutritional and lifestyle transition occurring in developing countries. This review presents evidence linking dietary nutrients with insulin resistance and its metabolic correlates, and also describes these issues from a Asian Indians and South Asian perspective. Despite possible influences from genetic and perinatal factors, diet and physical activity are likely to have greater and often overriding influence in pathogenesis of the insulin resistance, the metabolic syndrome, and T2DM. In animal studies, a link has been established between dietary nutrients and insulin resistance. However, in human studies evidence is not as strong as in animals. Data suggest that dietary omega-3 polyunsaturated fatty acids (PUFAs) improve lipid profile and may have beneficial effect on insulin resistance. Dietary saturated fatty acids intake is positively associated with insulin resistance. Also, low glycaemic index foods and whole grain intake decrease insulin resistance. Importantly, high carbohydrate diets increase plasma triglycerides, cause hyperinsulinaemia and decreases low-density lipoprotein cholesterol. Among micronutrients, high magnesium and calcium intake have been reported to decrease insulin resistance. High intake of dietary carbohydrate and omega-6 PUFAs, low intake of omega-3 PUFAs and fiber, and high omega -6/omega-3 PUFAs ratio have been reported in South Asians. Our recent investigations have shown that increased dietary omega-6 PUFAs and saturated fat intake are significantly associated with fasting hyperinsulinaemia and sub-clinical inflammation, respectively. Such imbalanced diets contribute to high prevalence of insulin resistance, the metabolic syndrome and T2DM in South Asians and Asian Indians.