The glycemic index, or GI, is a measurement of how quickly different carbohydrates increase your blood glucose after you consume them. The glycemic index was introduced in the early 1980s by Dr. David Jenkins at the University of Toronto as a means to assist diabetics in menu preparation. Glucose, with a GI value of 100, is the standard against which other foods are measured. Honey, with a GI of 55 to 60, enters your circulation more quickly than xylitol, a sugar alcohol with a GI of around 8.
Carbohydrate Digestion
Whenever you consume carbohydrates, they are broken down into smaller molecules by digestive enzymes in your gastrointestinal tract. Simple sugars, polysaccharides and starches are all reduced to their simplest constituents so they can be absorbed into your bloodstream. Glucose, fructose and galactose -- the end products of carbohydrate digestion -- pass readily through your intestinal wall and enter your circulation. After reaching your liver, fructose and galactose are converted to glucose, which is your body's preferred fuel. Glucose and fructose, the primary sugars in honey, cause a relatively rapid increase in your blood glucose when compared to xylitol.
Glucose and Insulin
Insulin is a hormone produced by your pancreas in response to rising blood glucose levels. Insulin stimulates the cells of your liver, muscles and adipose tissue to absorb glucose, which is either burned for energy or stored as glycogen or fat. Higher GI foods introduce more glucose into your bloodstream in a shorter period of time, triggering a more robust insulin response from your pancreas. If you are diabetic, sweeteners with a low GI, such as xylitol, help to control your blood glucose level, thereby reducing your need for insulin.
Glycemic Load
Glycemic load, which is a modification of the glycemic index, makes it easier for you to decide how foods affect your blood glucose in "real-world" situations. While GI measures your glucose response to 1 g of a given carbohydrate, glycemic load determines the impact of a standard portion size of that same carbohydrate. Eating small amounts of high GI foods has the same impact on your blood glucose as eating larger amounts of low GI foods. Xylitol, a low-GI sweetener that's measured like table sugar, can be useful for people who are trying to control their blood glucose levels.
Considerations
Glycemic index and glycemic load are important nutritional concepts that allow you to compare the relative impacts of various carbohydrates on your blood glucose level. Different sweeteners have different effects on your blood glucose level, so they have been assigned different GI values. Xylitol, with a glycemic index of 8, has a much smaller impact on your blood glucose than honey, with a GI of 55 to 60. If you are concerned about sudden or dramatic increases in your blood glucose, xylitol might be useful for you. If you have not used xylitol before, it can initially cause diarrhea if you consume more than 30 to 60 g daily.
References
- "The American Journal of Clinical Nutrition"; Glycemic Index of Foods: A Physiological Basis for Carbohydrate Exchange; D.J.A. Jenkins et al.; March 1981
- "The American Journal of Clinical Nutrition"; International Table of Glycemic Index and Glycemic Load Values: 2002; K. Foster-Powell et al.; July 2002
- Oulu University Library: Xylitol
