Column 16, May 2009

Glycemic Index – Quality carbohydrate vs low carbohydrate

The low carbohydrate debate

Anyone looking at ways to get lean would have read the claims about low carbohydrate diets.

Adhering to such a regime often causes an initial fast weight drop, but on closer inspection we find that much of this can be attributed to loss of muscle glycogen (the body’s stored form of carbohydrate) and associated fluid stores.

Low carbohydrate diets also claim to work by preventing the rapid rise in blood sugar that can be seen after certain high carbohydrate meals. This spike in blood glucose causes insulin levels to rise, telling the cells in our body to take up the glucose quickly, and use it for growth and storage of lean tissues, glycogen and fat.

But don’t I need carbohydrate to exercise?

Yes! Carbohydrate is the body’s main source of fuel for moderate to high intensity exercise, which is why many who start on a low carbohydrate regime find themselves too tired to train hard.

In addition, a low carbohydrate diet can cause gradually increasing weakness, dizziness, headaches, confusion, abdominal pain, irritability, nausea and vomiting, sleep problems and bad breath.

How can I maintain a high carbohydrate diet and still lose weight?

Follow a healthy, balanced diet, choosing mostly low glycemic index carbohydrates. A recent study from the University of Sydney compared healthy diets containing high or low GI carbs, and high or low protein, on heart health and weight.

They concluded that those on the high-carb, low GI diet lost the most fat, and reduced their ‘bad’ (LDL) cholesterol the most.

What is Glycemic Index (GI)?

The glycemic index measures the effect of carbohydrate foods on blood sugar levels, compared with pure glucose. Glucose is given a value of 100 as it is very rapidly digested and absorbed, resulting in marked fluctuations in blood sugar levels. Foods can then be grouped as:

Low GI	Moderate GI	High GI
<55	55-70	>70

What are the benefits of a low GI diet?

Reduced appetite and hunger

Weight loss

Improved glucose control in those with diabetes

Lowered blood lipids

Reduced risk of developing heart disease and diabetes

Is the glycemic index affected by serving size?

Yes. GI is usually measured based on a portion containing 50g of carbohydrate, however the amount of carbohydrate in a ‘usual’ serve of a particular food varies greatly, altering the impact on our blood glucose.

Glycemic Load (GL) takes quality (GI) and quantity into account to predict the effect on our blood glucose. GL = GI x amount of carbohydrate divided by 100.

A particular meal can be categorized as:

Low GL	Medium GL	High GL
10 or less	11-19	20 or more

Example 1) Pumpkin has a high GI of 76, but a usual serving size contains only 7g of carbohydrate, therefore the GL = 76 x 7 divided by 100 = 5.3 = Low GL

Example 2) Fresh pasta has a low GI of 40, however a pasta meal at an Italian restaurant may contain 90g of carbohydrate, therefore the GL = 40 x 90 divided by 100 = 36 = High GL.

Should I just reduce sugars and increase starchy carbohydrates?

Unfortunately it’s not that simple. Many factors affect GI, including the type and amount of carbohydrate, the amount and form of fiber, processing and cooking, and the presence of protein and fat.

Potatoes for example have a high GI, whereas apples (which contain the sugar fructose) have a low GI. Potato chips also have a low GI due to the fat content, but they should not form a regular part of a healthy diet.

Some products have started to add GI to the label. Alternatively you could check out http://www.shoeclinic.co.nz/l?lnum=103853 .

Practical Suggestions

High GI Foods

Healthy Low GI Alternatives

Breads & Cereals
White Breads	Sourdough
Wholemeal Breads	Most Vogels & Burgen breads/ heavy rye breads/
Cornflakes/Wheat Biscuits/Puffed Rice & most	Buckwheat bread
processed cereals	All Bran/Rice Bran/Oat Bran/Special K
	Porridge/Some whole grain cereals and mueslis (not
	puffed whole grain)
Starchy Vegetables/Rice
Potatoes	Kumara/Yams/Taro
White rice	Basmati/brown rices
	Sushi
	Barley/Buckwheat
	Pasta/noodles
Legumes and Nuts
	Most beans/chickpeas/lentils and nuts
	Hummus
Fruit
Over-ripe bananas	Most other fruit
Raisins
Drinks
Soft drinks	Soy milk/milk smoothies
Sweetened fruit drinks	Up & Go
Sports drinks*	Sustagen
	Yakult
Dairy & Soy
	Unsweetened or fruit Yoghurt
	Custard
	Reduced fat milk and soy milk
Snacks
Most cakes/muffins/biscuits	Burgen fruit bread
Most muesli and sports bars*
Sweets
Most crackers	Arnotts Vitawheats

* sports bars and drinks, as well as other high GI foods are important during and after prolonged, high intensity workouts. At this point these foods will speed muscle glycogen replenishment, rather than cause fat storage.

Other guidelines to lower the Glycemic Load

Spread meals out over the day, rather than eating large amounts

Use low fat vinaigrettes with meals – vinegar lowers the GL of a meal

Include a small amount of lean protein food (eg low fat dairy, lean meat/fish or chicken) or healthy fats (eg avocado, olive oil, peanut butter) with meals and snacks to slow digestion and absorption.

Recommended Reading

Jennie Brand-Miller and co-authors have published numerous books on GI including:

The Diabetes and Pre-diabetes Handbook, The New Glucose Revolution and The Low GI Diet.