The Glycemic Index/Load

The Glycemic Index/Load: What is it and how does it work in the body?

• At present, the American Diabetes Association (ADA)' does not recognize a role for the glycemic index in the prevention of disease. On the basis of its review, diets with a low glycemic index may reduce postprandial glycemia but may be difficult to maintain long term.

• The ADA holds that additional evidence to support the glycemic and lipid benefits of low-glycemic index diets is needed. Data from a later review of the literature, however, suggest that glycemic index information should be incorporated into exchanges and teaching materials specifically for disease prevention of diabetes, cardiovascular disease, inflammation, and, possibly, some cancers. In this chapter, the definitions of glycemic index and glycemic load are reviewed, and studies demonstrating their possible use in disease prevention are provided.

• The glycemic index (GI) has proved to be a useful nutritional concept-the chemical classification of carbohydrate (simple or complex, sugars or starches, available or unavailable)-that fosters new insights into the relationship between the physiologic effects of carbohydrate-rich foods and health.

• The Gl measures how quickly a consumed carbohydrate affects postprandial serum glucose levels in a specified time. By definition, the Gf compares equal quantities of available carbohydrate in foods and provides a measure of carbohydrate quality.

• Available carbohydrates can be calculated by summing the quantity of available sugars, starch, oligosaccharides, and maltodextrins. In effect, the Gl is an indicator of the relative glycemic response to dietary carbohydrates.

• Glucose and white bread are often used as the "gold standard" because they cause the fastest and most dramatic rise in glucose levels. In the evaluation of individual foods, either glucose or white bread is assigned a value of 100, the highest index possible.

• All other foods are then assigned proportionately lower values on the basis of how they affect serum glucose levels in comparison with glucose or white bread." The Gl is now widely recognized as a reliable, physiologically based classification of foods according to their postprandial glycemic effects.

• For example, in healthy individuals, step-wise increases in GI have been shown to predict stepwise. elevations in postprandial blood glucose and insulin levels.

Important points to consider

• The Gl measures how quickly a consumed carbo-hydrate affects postprandial serum glucose levels in a specified time.

• A low Gl has correlated with a reduction in hemoglobin A1c, elevated high-density lipoprotein concentration, and lower levels of triglycerides.

• Increase consumption of fruits, vegetables, and legumes. Consume fruits that are underripe instead of overripe (e.g., bananas).

• Consume grain products processed according to traditional rather than modern methods (e.g., al

  dente pasta, stone-ground breads, old-fashioned oatmeal) Avoid puffed grains and finely ground flour or grain products.

• Acid in food lowers Gl (i.e., sourdough bread has a lower Gi than non-sourdough bread).

• Limit intake of potatoes and concentrated sugars.

• Consume high glycemic foods with fat and protein to reduce their Gl. In general, reduce consumption of "white foods" (potatoes, breads, pasta) and increase consumption of multicolored whole, no processed foods.

Key Web Sources

• http://www.glycemicindex.com

• http://www.fammed.wisc.edu/sites/default/files//webim-uploads/documents/outreach/im/handout glycemic index patient.pdf

• http://www.ajon.org/content/76/1/5/11.expansion