The glycaemic index (GI) is a rating that shows how quickly a food containing carbohydrates affects your blood sugar (glucose) level when that food is eaten on its own.
High GI foods
Carbohydrate foods that are broken down quickly by your body and cause a rapid increase in blood glucose have a high GI rating. High GI foods include:
- sugar and sugary foods
- sugary soft drinks
- white bread
- potatoes
- white rice
Low and medium GI foods
Low or medium GI foods are broken down more slowly and cause a gradual rise in blood sugar levels over time. They include:
- fruit and vegetables (not dried)
- pulses
- wholegrain foods
Are low GI foods healthier?
Some low GI foods, such as wholegrain foods, fruit, vegetables, beans and lentils, are foods we should eat as part of a healthy balanced diet.
However, using the GI to decide whether foods or combinations of foods are healthy can be misleading. Foods with a high GI are not necessarily unhealthy and not all foods with a low GI are healthy. For example, watermelon, bread, rice and potatoes are high GI foods, while chocolate pudding has a low GI value.
Also, foods that contain or are cooked with fat and protein slow down the absorption of carbohydrate, lowering the GI. For example, crisps have a lower GI than potatoes cooked without fat.
If you only eat foods with a low GI, your diet may be unbalanced and high in fat.
Find out more about eating a healthy balanced diet.
Can low GI foods help me lose weight?
Low GI foods, which cause your blood sugar levels to rise and fall slowly over time, may help you feel fuller for longer. This could help control your appetite and may be useful if you’re trying to lose weight.
However, as mentioned, not all foods with a low GI are healthy. Therefore, relying on GI may not be a reliable way to decide whether foods or combinations of foods are healthy.
Read more information about losing weight.
Can the glycaemic index help people with diabetes?
If you have diabetes, it’s useful to understand the GI. This can help you to:
- eat high GI foods with care
- avoid eating only high GI foods
Eating low GI foods can help keep your blood sugar level more stable throughout the day.
Diabetes is a long-term condition caused by too much sugar in the blood. Normally, the hormone insulin controls the amount of sugar in the blood. However, in people with diabetes, there is either not enough insulin, or the insulin that’s there doesn’t work properly.
If you have diabetes, to help control your condition, it’s important to eat a healthy balanced diet. If you you’ve been advised to make changes to your diet or you need advice, a diabetes dietitian can help you work out a plan for your diet.
See the Diabetes UK website for more information on GI and diabetes.
Read the answers to more questions about food and diet.
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