The Glycaemic Index - How it can help you

Not all carbohydrates are equal, says Nutritionist Catherine Saxelby. 'Slow carbs' are now seen as the key to help you shed weight and stabilise blood sugars.

Introduction

In the past nutritionists recommended high fibre and whole grain foods such as bran cereals, brown rice, potato and baked beans, to help fill dieters up and keep blood sugar levels steady for those with diabetes. Now a more scientific approach is gaining momentum based on how slowly or how rapidly a carbohydrate food is digested and absorbed. Known as the Glycaemic Index, it is not only useful for those with diabetes but has been shown to help anyone wanting to loose weight, control heart disease and boost their energy levels.

What is the Glycaemic Index?

The Glycaemic Index (or G.I) is a ranking of foods from 0 to 100 that tells us whether a food will raise blood sugar levels dramatically, moderately or just a little. The term was first coined in 1981 by a Canadian professor Dr David Jenkins but has taken a long time to be put into standard dietary practice.

Low GI = 55 or less
Moderate GI = 56 to 69 inclusive
High GI = 70 or more

Starch vs sugar

Originally nutritionists believed that starchy carbohydrates like bread and potatoes were "complex" and took longer to be digested and absorbed than "simple" sugars, which caused a rapid rise of blood sugar (difficult for someone with diabetes to handle). Hence sugar was banned from diabetic diets and sugar-free recipes for desserts, cakes and biscuits became a necessary part of therapy (even though they may have been high in fat).

Now research from Canada and Australia has turned this notion on its head. It showed that many starchy foods like white bread, potato and many types of rice are digested and absorbed very quickly, giving them a high GI. It also showed that sugar has only a moderate GI so affects blood sugar quite modestly, often less than bread or rice.

Low carbohydrate diets - only part of the answer

If you are trying to drop kilos, cutting out all carbohydrates is not the solution nor is it practical, despite the claims from popular "no-carb" diet books. The body requires some carbohydrate for fuel for the brain, nervous system and red blood cells (these rely exclusively on carbohydrates in the form of glucose to keep working).

So eliminating all carbohydrates means that these diets often leave you feeling irritable and low in energy. And carbo foods such as grainy breads, pasta, starchy vegetables like pumpkin and sweet potato, and legumes provide fibre and important vitamins that the body needs.

Which carbohydrates should you choose?

The key is to:

1. Modestly reduce your intake of carbohydrates (usually easiest if you cut out 'extras' like lollies, chocolate, cakes, biscuits and soft drink).
2. Choose some 'slow carbs' with a low GI which will take longer to be digested and slow the return of hunger.

How the GI can help your weight

With modernization our lifestyles have become less active and our diets more highly processed. These two factors have played a big role in Australia's rising rate of overweight and obesity.

Originally cutting out fats was believed to be the simplest easiest way to cut kilojoules, as fats provide 37 kilojoules per gram - twice as much as carbohydrate at 16 and protein at 17 kilojoules per gram. Research into the GI has revealed that the type of carbohydrate Australians choose has not helped their weight loss efforts.

These modern carbohydrates enter the blood stream quickly, raising blood sugar levels and triggering a surge of insulin. They flow through our bodies quickly but leave us feeling hungry soon after.

Low GI foods help suppress your appetite

Professor Jennie Brand Miller, a leading researcher in the GI and author of 'The New Glucose Revolution' says: "One of the biggest challenges to losing weight can be feeling hungry all the time, by this gnawing feeling is not a necessary part of losing weight. Foods with a low GI are amongst the most filling of all foods and delay hunger pangs for longer."

Switching some of your carbohydrates from high to low GI is one strategy to make your diet more satisfying and filling without eating more kilojoules (see table for easy swaps). For example, a potato has around the same carbohydrate and kilojoules as pasta but the pasta takes longer to be digested so delays the return of hunger before the next meal. A standard diet sheet would let you interchange one medium potato for half a cup of cooked pasta but they're not treated the same but the body.

GI and snacks

Professor Brand Miller believes snacks are probably one of the most important foods to target with low GI substitutions. "Carbohydrate tends to have a stronger effect on our blood glucose level when eaten alone," she comments.

10 low GI snacks

1. low fat yoghurt
2. corn-on the-cob
3. slice of raisin toast or fruit loaf
4. snack pack of fruit in natural juice
5. 20 cherries
6. small can baked beans
7. 5-6 dried apricot halves
8. slice of grainy toast with jam
9. low fat flavoured milk
10. large peach or pear

Go GI for diabetes

Professor Brand-Miller believes the GI has many benefits for those with diabetes because "not only is it important in treating people with diabetes, but it may also help prevent people getting diabetes in the first place and possibly even prevent some of the complications of diabetes."

Swapping some high GI foods in your diet for low GI alternatives as in our "putting it into practice" meal plan (see below) can go a long way helping blood sugar levels.

Putting the GI into practice

High GI

Breakfast: Wheat flake or biscuit cereal with low fat milk, Wholemeal toast with a scrape of margarine and cheese, Tea, water or fruit juice

Morning Tea: Plain sweet biscuits

Lunch: Ham and salad sandwich on white bread roll, Fruit muffin, Orange flavoured soft drink

Afternoon Tea: Puffed crisp bread with scrape of margarine

Dinner: Lean grilled steak or skinless chicken fillet, Jacket potatoes, Green salad no dressing

Supper: Scoop chocolate ice cream

Low GI

Breakfast: Porridge, All-Bran™ or natural muesli with low fat milk Toasted Multigrain™, Ploughman's wholegrain™ or Multigrain 9-grain™ with a scrape of margarine and cheese Tea, water or fruit juice

Morning Tea: Toasted fruit loaf with scrape of margarine

Lunch: Ham and salad Pita Pocket, Fresh fruit salad, Low fat flavoured milk

Afternoon Tea: Low fat fruit yoghurt

Dinner: Lean grilled steak or skinless chicken fillet, Three bean mix and pasta salad, Green salad with oil-vinegar dressing

Supper: Scoop low fat vanilla ice cream and sliced banana

Want more information?

Read about the GI in The New Glucose Revolution by Jennie Brand-Miller, Kaye Foster-Powell, Assoc Prof Stephen Colagiuri (Hodder Headline Australia)

http://www.glycemicindex.com/
http://www.gisymbol.com/

Catherine Saxelby is a dietitian-nutritionist and author of Nutrition for Life (Hardie Grant Books). This article first appeared in Super Food Ideas magazine in Feb 2003.
For more information, visit her website: http://www.foodwatch.com.au/