How Much Do You Know About Glycemic Index?

GI (Glycemic Index) is "glycemic index",simply referred as GI. It is an indicator that reflects the degree to which food causes blood sugar to rise in the human body, and is the response to the body's blood sugar production after ingestion. In other words, it is the proportion of blood sugar that rises when we take food into the body(relative to when we eat glucose).

Simply put, the easier the food that quickly raise blood sugar, the higher the GI value, such as sugar and starchy foods. On the contrary, foods that raise blood sugar much slower with more stable blood sugar, and have a strong feeling of satiety will have a lower GI value, such as fatty foods and high-protein foods.

Food GI value classification

Foods with glycemic index below 55 are considered as low GI food;

Foods with glycemic index between 55 and 69 are considered as medium GI food;

Foods with glycemic index above 70 are considered as high GI food.

But low GI ≠ low calories!

The GI value is not a caloric value. The glycemic index of food is based on the carbohydrate content of the food. Many fatty foods have low GI values, but too much fat not only means higher calories, but also reduces insulin sensitivity. Many fruits contain fructose, which is low in GI but high in calories. For example, banana has a GI value of 52 due to the presence of dietary fiber, phenols and other ingredients, making them a low-GI food, but with a sugar content of more than 20%. Therefore, low GI food does not mean that you can eat more and does not gain weight. We still need to control the total calories and have a balanced diet.

There are many factors that affect GI, the main ones are

1.Amount and type of carbohydrates in food.

Both fructose and glucose are monosaccharides, but due to different absorption and metabolism pathways, the GI of fructose (23) is significantly lower than that of glucose (100). Monosaccharides and disaccharides have simple structures and can be absorbed directly, so they have a higher GI. Starch is a polysaccharide, and its structure determines the level of GI. Amylopectin is easily broken down and digested faster than amylose, so its GI is higher. Prebiotics (such as fructooligosaccharides, isomaltooligosaccharides, etc.) are good substitute for sugar, and their sweetness is low (generally 0.4-0.6,) and cannot be digested and absorbed by the human body itself. They can only be used by the beneficial bacteria of human intestines. The ideal energy supply and sweetening substance is isomaltulose.

2.The physical and chemical properties of food.

It mainly includes food matrix composition, starch particle size, moisture content, and pH, etc. Firmly embedded starch (such as whole grain wheat) has a lower GI than puffed and loose starch (such as wheat flour). Insoluble starch (such as cellulose) has a lower GI than soluble starch (such as mung bean starch). Alkali-Added Pasting(such as dietary alkali steam bun, cooked rice porridge) will increase the GI of starch.

3.Food processing and cooking methods.

Generally speaking, the more finely processed the food, the easier it is to be absorbed and the greater the glycogen effect; and the longer the same raw materials are cooked, the higher the GI of the food.

4.Content of other food ingredients.

It refers to fat, protein, dietary fiber, antinutrients, and organic acids. When the same amount of available carbohydrates is available, increasing protein can stimulate a higher insulin response, fat can help delay gastric emptying, and dietary fiber (such as resistant dextrin) can delay starch degradation through wrapping effect. Taking in staple food with meat and vegetables can also lower the GI of the staple food.