What is the glycaemic index (GI)?

GI can be a useful tool in your armoury of healthy eating and including more low-GI carbohydrates in your diet can be beneficial to your health.

But the GI needs to be kept in perspective: it should not be used in isolation and we can’t use it to justify eating more chocolate!

What is the glycaemic index?

The glycaemic index measures how carbohydrate foods act when they are digested. It’s a bit like the story of the hare and the tortoise. They are having a race and the hare races ahead but burns out, exhausted, along the way. Meanwhile, the tortoise moves slowly but steadily along and ends up winning the race.

Foods with a high GI are like the hare: the carbohydrate quickly breaks down to glucose and is absorbed into the blood. This sends your blood glucose (sometimes called blood sugar) zooming up and makes your pancreas work harder, producing more insulin to get it back down to normal.

On the other hand, low-GI foods act like the tortoise. They are slowly digested so the glucose trickles into your blood at a far more sedate rate, allowing a more gradual rise in blood glucose, which keeps you feeling fuller for longer.

There can be times when we need a quick burst of energy, but for long-term health and a steady supply of energy all day long, we are better to follow the example of the tortoise: slow and steady wins the race. That means, when it comes to eating carbohydrate foods, it is sensible to choose ones with a low glycaemic index more often.

Glycaemic index range

Low GI = 55 or less
Medium GI = 56-69
High GI = 70 or more

The most useful way to use the GI is to think in terms of substituting high-GI carbohydrates with low-GI carbohydrates. GI is less useful when foods contain a low percentage of carbohydrate, for example peanuts have only 8% carbohydrate.

The GI value is not fixed. GI values indicate the average glycaemic response to a food when measured in scientific studies: your response could be very different. The GI of fruit and vegetables varies between varieties, countries and how they are prepared.

Bread is an example of a food with a wide range of GI values. White and wholemeal bread typically have a high GI, whereas whole grain bread is low-GI. With so many different varieties on the market, and if its GI value is not stated on the label, how do you know whether your bread is low-GI bread? Professor Jim Mann recommends a simple procedure that he calls ‘the flap test’. Pick up a thick slice of bread and shake it. If it ‘flaps’ then it is probably high-GI as true whole grain (and hence low-GI) bread should be too dense to flap.

To find out the GI of a particular food, go to The Official Website of the Glycemic Index and click on 'GI Database'.

Low GI impact on health

Choosing low-GI carbohydrates may help if you identify with any of the following:

I want to lose weight
I often feel hungry and can’t help snacking on naughty stuff
I’m always tired
I have diabetes and need to improve my glucose and lipid levels
I am at risk of heart disease
I have high cholesterol
I exercise a lot

Regularly choosing low-GI instead of high-GI carbohydrates can help reduce your risk of developing obesity, heart disease and type 2 diabetes.

http://www.healthyfood.co.nz/articles/searchcategories?vocabulary_name=hfm.categories.foodandnutrients&catalog_index=foodandnutrients_categories&vocabulary_term=carbohydrates