Harnessing the Power of Glycemic Index Beyond Diabetes Control

There is a lot of evidence to support the growing importance of the GI and GL of diets. The link between high GI and GL diets to the risk of type 2 diabetes has been established recently.

The concept of 'Glycemic List' was first proposed by Prof. David Jenkins of the University of Toronto in 1981. The Glycemic Index (GI) of a food refers to the property of the food to increase the blood glucose level and is a measure of the 'quality' of carbohydrates. Glucose or white bread is used as the comparator. The GI of glucose is taken as 100 and the GI of other foods is given as a percentage of this. Thus, the GI of food is classified as low GI (under 55), medium GI (56-69), and high GI (over 70). The GI multiplied by the amount of the carbohydrate consumed, determines the glycemic load (GL).

Many nutritionists strongly believe in the deleterious effect of consuming diets with high GI and conversely the beneficial effects of taking diets with low GI. Others accept that this is too simplistic an approach. They argue that carbohydrates are only one of the macronutrients of food and the quality of protein and fat are ignored if only GI is used to assess the quality of a diet.

However, there is a lot of evidence to support the growing importance of the GI and GL of diets. The link between high GI and GL diets to the risk of type 2 diabetes has been established recently. However, what is less known is the association of high GI less carbs with cardiovascular disease and mortality. The Prospective Urban Rural Epidemiology (PURE) study, of which we are also a part, involves 137,851 members in 20 countries (including India) in five continents who have been followed for decades. In a paper distributed in the New England of Medicine in 2021, the association of the GI and GL of diets with cardiovascular disease has been explained. By using country-explicit food frequency questionnaires to assess the GIs and GLs of various diets in different countries. The diet with high GI was associated with major cardiovascular events including deaths across all ethnicities. This was an eye-opener regarding the importance of the GI of foods because until this study was published, it was not known that the importance of GI extends beyond diabetes.

These findings are particularly relevant to India and South Asia where carbohydrate consumption in the form of high GI white rice or wheat, forms the bulk of calories, leading to a very high GL of our diet. Hence all attempts should be made to reduce the GI and GL of our diets. This could help, not only in the prevention and control of diabetes but also in reducing the incidence of cardiovascular disease which occurs at much younger ages in India.

In the follow-up after nearly 12 years, 7,326 (5.7%) cases of type 2 diabetes occurred. A diet with a higher GI was significantly associated with a higher risk of diabetes. Participants in the highest quintile of the GL had a higher risk of incident type 2 diabetes compared with those in the lowest quintile. GI's association with diabetes was stronger among people with a higher BMI than those with a lower BMI.

Examples of diets with low GI include brown rice, steel-cut oats, legumes, pulses and beans, organic fruits like apple and guava, vegetables like spinach, lettuce, brinjal, broccoli, tomatoes, paneer, soya, seed, non-starchy vegetables, and dairy products.

Diets with high GI include sugar and sweets, white rice, maida, potato, white bread, sweetened drinks, jaggery, cornflakes, and cookies. Sugar, sugary beverages, white polished rice, potatoes, white bread.

• The findings of an international study suggest that consuming low glycaemic index and low glycaemic load diets might delay the development of type 2 diabetes.

• They also found a strong association between glycaemic index (GI) and the risk of type 2 diabetes among people with a higher Body Mass Index (BMI).

• GI ranks carbohydrates- containing food based on the blood glucose response, post-prandial or after a meal. The higher the blood sugar reading, the higher will be the GI.

If diets with high GI, i.e., the 'bad' carbohydrates, are replaced with 'good' carbs which have low GI and this is combined with adequate physical activity (exercise), it could help to curb the growing incidence of premature cardiovascular disease in India.