Carbohydrate Classifications

Simple or Complex?
Mono- and disaccharides are also classified as “simple” carbohydrates, and polysaccharides as “complex”. This is an outdated mode of carbohydrate classification and there is currently no use for characterizing carbohydrates in this manner. This classification system has been replaced by Glycemic Index, discussed below.

High Glycemic Index (HGI) or Low Glycemic Index (LGI)?
This newer classification system assesses the ability of the carbohydrate to elevate your blood glucose levels (glycemic response). The index uses either glucose dextrose) or white bread as the standard to which all other carbohydrates and foods are compared. On their respective scales, glucose (dextrose) or white bread is assigned an arbitrary value of 100. Therefore, using glucose (dextrose) as a reference standard of 100, a carbohydrate resulting in 70% of the elevation in blood glucose would be assigned a value of 70. Glycemic response tests are done by ingesting 50 grams of the carbohydrate/food in question, and measuring the blood glucose level at two hours.

Many factors influence the glycemic index of a carbohydrate, and include size of the molecule, type of component monosaccharides, degree of thermal processing, contents/timing of the previous meal and the make-up of other co-ingested foods. Because fructose and galactose must be converted to glucose by the liver first before they can elevate the blood glucose level, they have a low glycemic index i.e. this process takes time, resulting in slower increases in blood glucose. On a 100 point scale, fructose has a GI of 24, and galactose 22. These low GI scores mean that these substances are ‘slow burn’ carbohydrates. Use of these carbohydrates may lead to the body’s overdependance on using its’ glycogen stores, meaning eventual bonking. This concept is backed up by good research with respect to galactose, and the same problem can be reasonably inferred to exist with fructose (36). Carbohydrates, especially in the heat, must be able to supply quick energy, so the closer to 100 on the GI scale, the better. All high GI carbohydrates are immediately available and ready to use by the body once absorbed because they require no processing in your liver, giving you the energy you need now to fuel performance; they are therefore also called ‘fast burn’ carbohydrates. Dextrose is certainly in this category and also has the benefit of being easy to digest and absorb, with no remnants passing into the large intestine. Polysaccharides like maltodextrin, glucose polymers, amylopectin and amylose also have GI scores around 100, but may be associated with incomplete digestion, as discussed above, a process potentially detrimental in the heat.