This is a guest blog post by Dr. Ayala Laufer-Cahana M.D.

Have you ever noticed the low glycemic Index (GI) term on food packaging and wondered what it means?

The GI also makes frequent appearances in many popular commercial diets and diet books – including the South Beach Diet, Nutrisystem, the Zone diet and Sugar Busters.

Is a low GI diet indeed healthier? Is it useful for weight maintenance?

What is the GI?

The glycemic index, developed initially for the treatment of diabetes, ranks carbohydrate-containing foods based on how they affect blood sugar levels when eaten in isolation. Carbs that break down quickly, like white bread and potatoes, have a high GI, and those that release sugar into the blood stream more gradually, like fruit, have a low GI. Foods are scored on a scale of 0 to 100.

Is low GI food better? Will it help me lose weight?

Blood glucose fluctuations elicit a cascade of hormonal reactions, which potentially affect both metabolism and hunger, and a low GI diet’s ability to decrease hunger and control weight regain showed some promise in a few short term studies.

Low GI corresponds quite often with the age-old understanding of what’s good to eat. Most highly processed grain products have a high GI, whereas minimally processed grains, whole fruits, legumes, and non-starchy vegetables tend to have a moderate or low GI.

On the other hand pure fructose and ice cream have a very low GI, table sugar and high fructose corn syrup have only a moderate GI, and potatoes and white rice are the root of all GI evil, with a GI of about 100.

A few other things to dampen down your enthusiasm for the GI: It’s difficult (and costly) to test, there’s inter-lab variability, although the type and proportion of sugar or starch in a food affects GI, so do a lot of other factors in the meal—the way the food’s been cooked, the presence of fiber, protein, fat, alcohol or acid will all affect the glucose response—and there’s plenty of inter-personal variability.

Finally, the GI of the food matters much less than how much of that food you’re eating.   To really make the GI useful you’ll need to calculate glycemic load (GL).  The GL takes into account the GI, the amount of carbs in that food and the portion size, and will be a better predictor of how your blood sugar will be affected by that certain meal component.

To be quite honest, even diligent adherence to GI charts will leave you guessing about your own sugar level fluctuations after a meal.

Creating processed low GI foods is easy!

If the GI concept really takes on, food processors will have an easy time creating new foods with the hot new low GI buzzword as a selling point: Replacing table sugar with fructose will lower the lab-tested GI. However, it most likely will add nothing to our health, and may even do harm.

In honor of my host, Fooducate, I’ll have to end with:

What to do at the supermarket

GI is helpful in the management of diabetes, but at this point, GI for weight-loss or for general well-being is neither practical nor is its validity fully established.

A better strategy is to look at the ingredients: The amount of added sugar in a food matters much more than its glycemic index.

Dr. Ayala

Ayala Laufer-Cahana M.D. is a pediatrician, artist blogger and co-founder of Herbal Water Inc.

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