Glycaemic Index- An Introduction

INTRODUCTION

Glycaemic index (GI) had been plagued with controversies and faced with scepticism and resistance by scientists and clinicians these past years. The concept had been questioned for its complexity, practicality and utility in the clinical setting (1-4). However, research done by Dr David J. A. Jenkin, Dr Jeannie C. Brand-Miller and Dr Thomas M.S. Wolever ,in particular, had proved time and again that the concept works (5-7). The term “glycaemic index” was first coined by Dr David Jenkins since 1981. Glycaemic index (GI) is the classification of foods based on their blood glucose-raising potential up to 3 hours after eating(6). Based on the GI concept, foods could illicit a high blood glucose level response (high GI foods), moderate blood glucose response (intermediate/moderate GI foods) or a slower rise in blood glucose response (low GI foods)(8).

The higher blood glucose level response from high GI food would result in hyperinsulinemia and is associated with the “metabolic” syndrome; faster weight gain in rats; increase risk of developing type 2 diabetes mellitus and coronary heart disease. “Metabolic” syndrome is characterised by insulin resistance, hyperlipidemia, hypertension and visceral obesity. It is clear that lifestyle diseases can be linked to high GI foods. (6) One of the risk factor of lifestyle diseases is obesity. Obesity is increasing worldwide in both developed and developing countries at such an alarming rate that it is becoming a global epidemic. With 30.4% of Singaporeans being overweight and 6% who are obese (NHS’ 98)(9), Health Promotion Board (HPB) have organise campaigns such as the National Healthy Lifestyle Programme, Healthier Choice Symbol (HCS) Programme and “Ask For” Programme. Despite numerous factors that cause obesity, diet remains to be one of the important and modifiable factors. Nutrition policies such as the Healthy Diet Pyramid and the Singapore Nutrition Guidelines advocate a diet that is high in carbohydrate, high in fibre, low in fat and moderate in protein. One of the implications of GI would be that it allows consumers to choose carbohydrate-rich food that would allow them to lose excessive weight.(

Lifestyle diseases such as diabetes mellitus is becoming a global health problem. In Singapore 15% of Singaporeans had been found to have diabetes mellitus, making it the sixth leading cause of death in Singapore (NHS’ 98)(9). Diabetes mellitus is a chronic disease caused by inherited and/or acquired deficiency in production of insulin by the pancreas, or by the ineffectiveness of the insulin produced (WHO 2003)(10). The consumption of low GI foods have been shown to reduce glycosylated hemoglobin, fructosamine, urinary C-peptide, day-long blood glucose, cholesterol and triglycerides. (11)

The GI concept can also be utilise by sportsmen in their strategies to enhance their performance. Low GI food is favourable towards athletes who need a more moderate and sustainable blood glucose level to enhance performance and endurance(12). Athletes can also benefit from the use of high GI food during and after competition. High GI foods should be used during events lasting longer than 90 minutes and during recovery, as it is important to restock the glycogen stored in the muscles. (