Food for Thought

There May Not Be a Magic Bullet, But We Still Have Commonsense
While numerous studies have consistently shown the glycemic index (GI) to be an effective tool in reducing blood glucose and insulin levels and the risks of certain diseases, it sometimes comes under criticism for not being the ‘magic bullet’ people sometimes expect in weight management.

The glycemic index is a powerful tool when used in the right way—that is, in combination with healthy eating, regular exercise, and medications as needed. The glycemic index is not intended to be used in isolation, with a disregard to commonsense. When used appropriately (ie in the context of a good diet), the GI can benefit overall health, promoting satiety and minimising diabetes risk and complications. The concept of the GI improves outcomes because it involves a more complete understanding of how carbohydrates are digested in the human body, recognising differences between different carbohydrate-containing foods (not just sugars versus starches), and how this will affect our physiological responses after consumption.

This leads to what some view as criticisms of the GI—that there is a such a broad range of GI values for different types of potatoes, for example, or that the GI of bananas will change depending on their stage of ripeness. However, we should not hold the GI to higher standards than we apply to other nutrient factors. We know the carbohydrate and fibre content of a banana will vary with ripeness, or its vitamin C content with storage. We would never expect the fat content of the local supermarket’s sausages to be exactly the same as that listed in the national tables of food composition.

While there are notable variances in GI (eg for different varieties of rice), there is also notable consistency. Apples, oranges, legumes and pastas have GI values in the 40s, white bread in the 70s, cornflakes in the 80s. Moreover, clinical intervention studies suggest that current GI tables are sufficiently accurate to produce differences in average blood glucose values in people with diabetes (Brand-Miller et al, Diabetes Care 2003).

Many people today are ready and willing to be active participants in their own health care, wanting to learn more about their conditions and how to manage them, even if this entails more than a few simple rules, and requires a deeper understanding of how their body works. Those who put the effort into understanding their physical condition and how they can help themselves will surely reap the long-term rewards and health benefits relating to the GI and beyond.

—Atarah Grysman, MSc, Glycemic Index Laboratories, Toronto