Foods containing carbohydrates that are easily digested, absorbed, and metabolized have a high GI while low-GI foods have slowly digestible carbohydrates that elicit a reduced postprandial glucose response.
Carbohydrates that are higher on the GI scale, given a value of 70 or higher, can contribute to a rapid rise in blood sugar levels, whereas foods lower on the GI scale can lead to a much slower response. Simple carbohydrates, such as table sugar, juice, sweetened soda, and candy, are generally higher on the GI scale, whereas most complex carbohydrates and high-fiber foods (such as whole grains, legumes, and vegetables) are much lower. Higher GI foods may be helpful for athletes during pre-training and post-training periods. Easily digestible carbohydrates provide a ready source of fuel when taken immediately prior to training, and in the post-training period, they provide immediate glucose for rapid glycogen replenishment.
The GI is a measure of how quickly a carbohydrate will raise an individual’s glucose levels when consumed on its own. On the GI scale, all carbohydrates are compared to glucose, which is given a GI value of 100 (Harvard Medical School, 2015).
Carbohydrate-rich foods can be categorized as below:
The above are relative to pure glucose (GI=100)