Glycaemic index (GI)

What are carbohydrates?

Carbohydrates, also known as ‘carbs’, are a major source of energy for your body. Your body breaks carbs down into glucose, which is used by your body’s cells for energy.

Foods that are high in carbs include:

• bread and pasta
• rice and grains
• fruits
• starchy vegetables

What is glycaemic index (GI)?

The glycaemic index (GI) (also spelled glycemic index) is a ranking of carbohydrates based on their immediate effect on blood glucose (blood sugar) levels.

The higher the GI, the faster your blood sugar will rise after you eat the food. Low GI carbohydrates break down more slowly, releasing glucose more gradually into your blood stream.

Why is GI important?

Australian diabetes guidelines recommend that people with diabetes include low GI carbohydrates in their diet, in place of high GI foods. This has been shown to reduce their average blood sugar levels, which reduces the chance of developing diabetes-related complications.

For people without diabetes, eating a low GI diet can help with weight management.

What are examples of low and high GI foods?

Lower GI foods include:

• oats (rolled, steel-cut or oat bran)
• grains (for example, pasta, rice noodles, quinoa, barley)
• legumes (for example, lentils, split peas and chick peas)
• starchy vegetables, (for example, corn and sweet potatoes)
• dairy foods (low fat, unsweetened)
• most fruits

Higher GI foods include:

• white bread
• corn flakes
• fruit juice
• instant noodles
• rice cakes
• potatoes

You can check the GI of different foods on The University of Sydney GI database.

Are low GI foods always a healthy choice?

GI is not the only factor to consider when making healthy food choices. Some low GI carbohydrates, such as chips, chocolate and ice cream, take a long time to break down because they contain large amounts of saturated fat. These are not a healthy choice, and it’s best to eat these types of foods only occasionally.

When making healthy choices, it’s important to look at a food’s overall nutritional value. Some important factors to consider are:

• total number of kilojoules
• any added sugar
• saturated fat content
• sodium (salt) content
• dietary fibre content

It’s also important to remember that even low GI foods should be eaten in moderation. A healthy diet will include a variety of foods from all 5 food groups. If you have questions or need more information and advice on healthy eating, ask your doctor or dietitian.

What can I do to lower the GI of the foods I eat?

Here are some tips for lowering the GI of your meal:

• Use dressings containing vinegar or lemon juice — acids can lower a food’s GI.
• Add fibre to your meal.
• Combine your carbs with protein to lower the overall GI of your meal.
• Eat potato or rice cooked but cooled, for example, as part of a salad.