We hear a lot about carbs and how they may help or harm us. But what we usually forget is that carbs, or carbohydrates as a more precise word, are not one single thing. Carbs are a group of molecules that have different physiological impacts. One aspect that varies in different carb molecules is the concept of the glycemic index. We have good carbs and bad carbs, based on their glycemic index.
But what is the glycemic index? Before digging further, let’s first take a look at an essential hormone in our body concerning carb metabolism: insulin.
A little bit about insulin
Our body regulates the level of blood glucose in a narrow range. Too high or too levels of blood sugar are both harmful and physiologically unacceptable. So we have a very sensitive system for controlling blood sugar. We have multiple hormones that increase blood glucose when it goes down a certain level. However, there is only one hormone that functions to lower our blood sugar, insulin. Insulin is the product of the pancreas. The time when we need insulin most is when we eat something. After eating, the carbs in the food are digested and then absorbed into the blood. This causes an increase in blood sugar, which triggers insulin secretion.
Impacts of insulin on carbs
Insulin functions to lower this load of glucose by:
- Directing muscle, fat and other tissues (except the brain) to take glucose from the blood and use it as a source of energy.
- Promoting the liver and muscles to store glucose in the form of glycogen, which the storage carb in the body.
These two actions result in the lowering of blood sugar back to normal after eating.
Effects of insulin on fat
Insulin has far more effects than just controlling the blood sugar level. Insulin facilitates the convert of excess glucose into fat. When we eat carbs, insulin makes most cells of the body use that glucose for their energy requirements. However, if glucose is present in excess of our body’s energy needs, insulin helps this excess glucose to convert into fat. This the way that eating extra carbs leads to overweight.
Glycemic index
Glycemic index (GI) is a measure that shows how much a food increases blood glucose level after eating. Pure glucose has a GI of 100. All other foods are compared to this. Therefore, the glycemic index of foods falls between 0-100. A food high in GI increases the blood glucose level more and sooner compared to a food with a low GI. Here you can see how glycemic index is measured, and here you can find a list of some common foods with their GIs.
We can group foods based on their GI:
Low GI (equal to less than GI 55)
Moderate GI ( GI 56-69)
High GI (GI 70 and more)
Why foods differ in their GIs? The GI depends on many factors: The physical structure of the food, the fibre content, the processing of the food, the presence of other materials like fat or acid, and the starch structure all can play a role in the GI.
Why is the glycemic index important?
The more the glycemic index of a food, the more is the amount of insulin secretion after eating. If we eat many of these foods, we will have multiple surges of insulin. This type of frequent insulin peaks is harmful to the body. Remember that insulin promotes fat production in the body. Longterm increases of insulin will cause fat deposition in the body, overweight, an increase in blood triglyceride level and proneness to type 2 diabetes. The less the glycemic index of the foods in our diet, the less the risk of conditions like cardiovascular diseases, diabetes and obesity,
