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By Mark Anthony, Contributing Editor | 02/24/2006
Once upon a time, carbohydrates were good, as long as they were low in fat and sugar. It was fat that made us fat.
In the late 1990s, carbohydrates became bad and had to be rationed, and fat made us skinny. Do we finally have carbs right? Do we have their number? More importantly, is that number the glycemic index (GI)?
In 1981, David Jenkins and colleagues at the University of Toronto developed a method to rank carbohydrates according to their immediate impact on blood glucose as a guide for diabetics. It was christened the "glycemic index."
The theory behind glycemic index is simple: As blood sugar rises after eating carbohydrates, insulin — secreted by the pancreas to metabolize sugar — rises in response. If you can predict the effect of eating different carbohydrates, you can avoid sharp insulin peaks and control blood sugar more effectively.
|Solo GI was the first clinically validated, low-glycemic line of nutrition bars on the market.|
At some point, glycemic index made the jump from a diabetic tool to a weight-loss regimen. It was gradual, actually, but picked up a head of steam after the demise of the Atkins Diet. In one best-selling diet book after another, low GI is now supplanting the low-carb message left over from the recently deceased "carbs bad, fat and protein good" fad.
Here again, the theory seems sound. If sugar enters the blood too rapidly, insulin will spike, cells will grab glucose too quickly to be used for immediate energy, thus favoring the storage of fat. Blood sugar will then drop dramatically, leaving you hungry for more carbohydrates. This will make overeating and obesity inevitable.
Many natural carb sources, such as beans and most whole grains, have a low GI. Lots of refined carbohydrates like white bread have a high GI. Many health experts believe there is a close link between the modern diet of highly refined foods and the epidemic of obesity and type II diabetes. So with low-carb mania dying and obesity still raging, many food manufacturers are stepping up to meet the demand for low-GI products.
At the same time, there are incongruities. Chocolate fudge cake has a GI of 38, almost identical to pinto beans with a GI of 39. Boiled potatoes, by far the most satisfying food on the satiety index, is at 101, while potato chips and pound cake are 54. Fava beans are at 79, higher than a donut with cinnamon and sugar at 76, and nearly the same as jelly beans at 80.
Some believe glycemic index is the silver bullet that will pull us out of the obesity trap. "I believe eating low-glycemic nutrition can address the growing, dual epidemics of diabetes and obesity, 'diabesity,' head-on," says Saul Katz, president of Solo GI Nutrition (www.solo-gi.com), Edmonton, Alberta.
"The glycemic index is a very important new tool that can help manufacturers become part of the solution, instead of contributing to the problem, by designing foods that deliver energy to our bodies as nature intended,” Katz continues. “That is why we developed Solo GI Low Glycemic Nutrition Bars, to address the need for sustained energy and hunger management between meals or on the run."
Solo GI was the first clinically validated, low-glycemic line of nutrition bars on the market. The product was honored by the Specialty Nutrition Group as the Most Innovative Product of 2004.
Despite the enthusiasm, GI is a concept with issues, not the least of which is the fact that GI is not an inherent property of food. GI is a measure of the impact on blood sugar over a two-hour period after eating 50g of a test food.
This measure is compared with that of 50g of a reference food (glucose or white bread), and expressed as a percentage of the reference — assigned a value of 100. The number is an average taken in only 10 subjects. A score of 70 or above is considered a high GI, 55-69 is medium and 54 and below is considered low GI.
Many factors affect GI, including fat, protein, fiber, food particle size, cooking method, moisture content, type of starch (amylose or amylopectin) and type of sugar (for example, glucose or fructose). GI can vary from lab to lab, person to person and even in the same person at different times of the day. This makes standardization difficult, if not impossible.
|Kellogg’s Kashi Go Lean rolls do not tout a low GI, but are marketed as providing "optimized glycemic response."|
Go Lean rolls were created around the aspect of glycemic load (GL), the relation of GI to grams of carbohydrate. Many nutritionists feel GL gives a more realistic picture than GI because we eat mixtures of ingredients, all of which affect blood glucose. Others point out foods with the same GL may vary significantly in glycemic response.
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