Glycemic index is the scale that rates the carb containing foods based on their ability to alter blood glucose levels
Breakdown of ingested carb food increases the blood glucose level. The rate at which a carb increases the blood glucose levels is called glycemic response. This plays an important role in deciding the glycemic index of food.
The food that contains simple carbs is metabolized quickly and so the blood glucose levels are increased rapidly. This indicates a high GI. Foods containing complex carb are digested slowly; the blood glucose levels are increased gradually. So the amount of insulin secreted is also less. Thus the blood glucose levels are maintained for a longer time (as compared to foods with higher GI) this gives a constant feeling of fullness over that period and so the food intake is less resulting in weight loss
Therefore a low GI food diet is recommended for weight loss as well as for patients with diabetes.
However, now the point is being debated that, whether applying GI to select food (especially in the case of diabetes patients) is really useful? It was felt that applying low GI food diet advice has not much clinical utility because in a mixed meal, the differences of GI are lost after all the products are taken together.
Effects of other components of a mixed meal also may alter the glycemic response. Using GI concept to select diets for diseases was considered as adding unnecessary complications and limitations to choosing a diet.
Not only GI of a food, but also other factors like its macronutrients, minerals, fiber, vitamins content, range of health advantages should be considered while deciding on a diet. However, now the importance of glycemic index is being recognized by adding GI rating of the products on nutrition information panel of food products.
The low glycemic index food diets are advisable for patients with problems like type 2 diabetes, insulin resistance, obesity, unstable blood sugar levels and hypothyroidism. It is also applied in management of PCOS.
Generally a low GI diet comprises of low glycemic index carb and lean protein. Easier way to follow a low glycemic index diet is to change the usual high glycemic index products with low GI ones.
- Instead if sugar-containing cereals, oat, barley, bran cereals are preferable
- Instead of white bread, switch over to whole grain or sourdough bread
- Incorporate more vegetables and fruits in the diet
- Basamati or brown rice is preferred over white rice
- Quantity of potatoes should be decreased or replaced with low starch vegetables
- Vinaigrette dressing over salad is advisable
- Include pasta, noodles etc in the diet.
Now glycemic load concept is being applied for deciding diets. But for diabetes patients, a diet applying glycemic index values is shown to be more beneficial. Diet based on GL values could be a mixture of food products, not always healthy for the diabetes patients. But incorporating a healthy low glycemic index food would improve blood sugar levels and provide necessary amounts of carb, fat and proteins. In low glycemic index food diet advice, it is preferable to:-
- Select slow carbs over low carbs
- Apply glycemic index to find carbs which are best suited
- Select portion sizes (especially of high carb foods) so as not to increase the total glycemic load of the diet.
According to the low glycemic index foods diet advice, it is not required to eat only low glycemic index foods for each meals, because the slow release of glucose by low GI foods continue for a longer period, almost up to the next meal and this decreases the glycemic effect of that meal. This is called ‘second meal effect’. However, it is still advisable to include at least one low GI food in each meal. Low GI diet does not mean not to eat other products. If a high GI product is included in diet, it should be combined with a low GI food like vegetables or legumes etc, so that total GI would be medium.
Advantages of low GI diet:-
- Decreases insulin resistance and insulin levels
- Helps in weight loss and weight control
- Deceases chances of heart diseases
- Helpful in the management of diabetes, as it affects glucose and lipid levels for better
- Decreases blood cholesterol levels, increases the HDL cholesterol concentration
- Increases physical stamina
- Gives feeling of fullness for longer periods
- Helpful even in management of PCOS
So it is indicated (by most of the studies) that applying GI in deciding a diet is important in management of chronic diseases.