In the past, carbohydrates were classified as simple or complex based on the number of simple sugars in the molecule. Carbohydrates composed of one or two simple sugars like fructose or sucrose (table sugar; a disaccharide composed of one molecule of glucose and one molecule of fructose) were labeled simple, while starchy foods were labeled complex because starch is composed of long chains of the simple sugar, glucose. Advice to eat less simple and more complex carbohydrates (i.e., polysaccharides) was based on the assumption that consuming starchy foods would lead to smaller increases in blood glucose than sugary foods. This assumption turned out to be too simplistic since the blood glucose (glycemic) response to complex carbohydrates has been found to vary considerably.
Thus the concept of glycemic index (GI) has been developed in order to rank dietary carbohydrates based on their overall effect on blood glucose concentration relative to a carbohydrate, generally pure glucose.
Glycemic Index (GI) is a method of ranking foods containing carbohydrates. GI measure the rate at which carbohydrates are broken down and appear in the blood as simple sugars. Low GI foods are absorbed by the body at a slower rate than high GI foods and provide greater satiety and sustained energy. Research shows that choosing low GI foods in conjunction with a healthy eating plan may be beneficial if you have diabetes or are at risk of developing diabetes.
Such foods can be classified into one of two broad classes, in respect to carbohydrate content i.e.
- “No carb” foods that consist entirely or mainly of proteins, fats, and/or water.
- “Good carb” foods that – because of the biochemical properties of the component carbohydrates, which are the main objectives and should constitute our carbohydrate sources.
Glycemic index (GI) measures the effect on blood glucose level after a food containing carbohydrates is consumed. Glucose is one of the body’s main sources of energy. It is the fuel used by the brain, muscles, and other organs of the body. Low Glycemic index foods affect blood glucose and insulin levels less and has a slower rate of digestion and absorption.
The goal of the low glycemic diet is to eat unprocessed and unrefined carbohydrates in combination with healthy proteins and fats to improve satiety by keeping digestion slow. To understand the low glycemic diet, everyone needs to understand the way that the carbohydrates affect blood sugar and that all carbohydrates are not created equal.
Low glycemic foods are often rich in fiber, protein, or fat, though it is not healthy to eat foods containing fats just for the sake of our blood sugar unless those fats are “good” (so- called unsaturated) fats.
Some strategies for lowering dietary glycemic index includes:
- To increase the consumption of whole grains, nuts, legumes, fruits, and no starchy vegetables.
- To decrease the consumption of starchy high-glycemic index foods like potatoes, white rice, and white bread.
- To decreasing the consumption of sugary foods like cookies, cakes, candy, and soft-drinks.
Carbohydrate-containing foods can be classified as high-GI (≥70), moderate-GI (56-69), or low-GI (≤55) relative to pure glucose (GI=100).