The Glycaemic Index (GI) is a rating system for foods containing carbohydrates. It shows how quickly each food affects your blood sugar (glucose) level when that food is eaten on its own.
It then ranks the quality of carbohydrates based on this score. Foods are ranked on a scale of 0 to 100, with pure glucose (sugar) given a value of 100. High GI carbohydrates cause blood sugar levels to spike and then crash, whereas low GI foods are digested and absorbed more slowly.
The GI principle was first developed as a strategy for guiding food choices for people with diabetes.
Carbohydrates, or carbs, a type of nutrient in foods, are an essential part of our diet since they provide fuel for the brain, most other organs and muscles during exercise. However, not all carbohydrate foods are equal. Different types of carbohydrate foods have properties that affect how quickly your body digests them and how quickly glucose enters your bloodstream. The three basic forms are sugars, starches and fibre. When you eat or drink something with carbs, your body breaks down the sugars and starches into a type of sugar called glucose, the main source of energy for cells in your body. Fibre passes through your body undigested.
Two main hormones from your pancreas help regulate glucose in your bloodstream. The hormone insulin moves glucose from your blood into your cells. The hormone glucagon helps release glucose stored in your liver when your blood sugar level is low. This process helps keep your body fuelled and ensures a natural balance in blood glucose. This slow release of glucose into the bloodstream is proven to be much more beneficial for the body – from improving energy levels to managing weight, diabetes and other health concerns.
Understanding the GI value of a food can help you make healthier food choices and improve your overall health in the long run. The GI value of foods is calculated in a food laboratory using valid scientific methods. There are three classifications for GI: