Glycaemic Index (GI) has become a familiar term over the past few years, and in 2004 Tesco became the first UK retailer to label their products as medium or low GI.
What does GI mean?
GI is a ranking system for carbohydrate-containing foods based on their effect on blood sugar (glucose) levels. GI runs from 0 to 100 and usually uses glucose - which has a GI value of 100 - as a reference point. The effect that other foods have on blood sugar levels are then compared with this.
- High GI Food = A food that is quickly absorbed by the body and tends to cause a higher rise in blood sugar levels
- Low GI Food = A food that is slowly absorbed by the body and tends to cause a lower rise in blood sugar levels
Examples
Low GI
(GI 55 or less) |
Medium GI
(GI 56 to 69) |
High GI
(GI 70 or more) |
| Pasta |
Couscous |
White Bread |
| Beans and lentils |
Pitta Bread |
Mashed Potato |
| Porridge |
New Potatoes |
White Rice |
| Apples |
Ice cream |
Watermelon |
GI and health
Diets that are based on low GI foods can be beneficial to health. The main benefit is for people with diabetes, but research into other areas suggests there could be benefits for weight loss and heart disease. Low GI and high GI foods can also be useful for sport.
- Diabetes: Reducing the peaks in blood glucose following a meal may have a role in preventing or reducing the risk of getting Type 2 diabetes. For those with diabetes, low GI foods can help maintain even blood glucose levels and can help avoid ‘hypos’ (low blood sugar levels).
- Weight loss: Because low GI foods produce a slow, steady rise and fall in blood sugar levels, they can help people to feel full for longer. These foods may therefore play a role in weight management by helping to control appetite, if used in combination with a reduced calorie intake and regular physical activity.
- Heart Disease: Research has shown that people who have an overall low GI diet have a lower incidence of heart disease. Lower GI diets have also been associated with improved levels of ‘good’ cholesterol.
- Sport: Low GI foods such as pasta can be eaten before a sport event to help the body store energy. High GI foods such as a sports drink can help replace energy immediately after an event or training, helping with recovery.
GI and healthy eating?
GI can be affected by a number of factors: fat and protein will lower the GI e.g. crisps have a lower GI than potatoes cooked without fat. Cooking method, processing, the ripeness of a fruit and the variety of a vegetable will also all affect a food’s GI rating. The structure and texture of a carbohydrate have an effect as well. Whole grains and high-fibre foods act as a physical barrier that slows down the absorption of carbohydrate and lowers the GI.
It is important to remember that a diet with a low GI can still be high in calories and fat. High GI foods don’t have to be avoided but by eating them with low GI foods, you can change the overall GI of a meal. For example, cornflakes (high GI food) with milk (low GI food)make a medium GI breakfast while a jacket potato (high GI food) eaten with baked beans (low GI food) makes a medium GI meal.
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