Glycaemic index and diabetes – Q&A
What else affects GI?
- Cooking methods: frying, boiling and baking
- Processing and the ripeness of fruit and certain vegetables
- Fibre: wholegrains and high-fibre foods act as a physical barrier that slows down the absorption of carbohydrate. This is not the same as ‘wholemeal’, where, even though the whole of the grain is included, it has been ground up instead of left whole. For example, some mixed grain breads that include wholegrains have a lower GI than wholemeal or white bread.
- Fat lowers the GI of a food. For example, chocolate has a medium GI because of it’s fat content, and crisps will actually have a lower GI than potatoes cooked without fat.
- Protein lowers the GI of food. Milk and other diary products have a low GI because they are high in protein and contain fat.
Is it ok to only focus on GI?
If you focus only on the GI of foods, without looking at other aspects, your diet could be unbalanced and high in fat and calories, which could lead to weight gain (making it harder to control your blood glucose levels) and increase your risk of heart disease. It’s important to think about the balance of your meals, which should be low in saturated fat, salt and sugar and contain plenty of fruit and vegetables.
The amount of carbs you eat has a bigger effect on blood glucose levels than GI alone. For example, pasta has a lower GI than watermelon, but pasta has more carbs than watermelon, so if you eat similar amounts of either of these two foods, the pasta will have more of an impact on your blood glucose levels. The most important thing to do is get your portion size right – once you do this, you will get an added bonus for choosing low-GI alternatives.
Low-GI foods in your healthy, balanced diet
It’s easy to include low-GI carbs in everyday meals:
- Choose basmati or easy cook rice, pasta or noodles. Or, try plantain, quinoa or bulgur wheat for a change.
- Eat wholemeal roti and include dhal in your meals.
- Use new potatoes instead of old potatoes – try sweet potatoes for a change.
- Instead of white and wholemeal bread, choose granary, pumpernickel or rye bread.
- Swap frozen chips for pasta or noodles.
- Try porridge, natural muesli or wholegrain breakfast cereals.
Educating yourself on GI
There are books that give a long list of GI values for many different foods. This kind of list does have its limitations. The GI value relates to the food eaten on its own and in practice we usually eat foods in combination as meals. Bread, for example is usually eaten with butter or margarine, and potatoes could be eaten with meat and vegetables.
An additional problem is that GI compares the glycaemic effect of an amount of food containing 50g of carbohydrate but in real life we eat different amounts of food containing different amounts of carbohydrate.
Note: The amount of carbohydrate you eat has a bigger effect on blood glucose levels than GI alone.