20 Chapter 2: Basic Nutrition Research shows that regular consumption of high GI foods can increase an individual’s risk for certain metabolic diseases such as cardiovascular disease, stroke, type 2 diabetes, metabolic syndrome, chronic kidney disease, gall stones and various types of cancer (Peterson & Rittenhouse, 2019). While regular consumption of high GI foods is not recommended for improving general health, if timed correctly, they can be used strategically, such as immediately post-workout to help replace and replenish used carbohydrates during exercise. For example, waiting to eat your favorite sugary cereal until after your workout. The Glycemic Index can be a useful tool, but has its limitations. The Glycemic Index rates food solely by the impact it has on blood glucose levels, and not by the quality or quantity of the carbohydrate being consumed. For example, watermelon has a GI rating of 80, which categorizes it as a high GI food and thus should be avoided. However, watermelon has few digestible calories in a typical serving. Conversely, a 2 oz. candy bar has a GI rating of 62, which categorizes it as medium GI food. Because of these limitations, Glycemic Load (GL) was developed to provide a more accurate assessment of carbohydrate food choices. Glycemic Load evaluates both the quality and quantity of the carbohydrate in food and is calculated by multiplying the GI rating of a food by the grams of carbohydrate per serving, then dividing the sum by 100. Watermelon, for instance, has 6 grams of sugar per serving, whereas a candy bar has 40 grams. This means that watermelon has a GL rating of 5 (i.e., GI rating of 80 x 6 g of sugar per serving / 100), which categorizes it as a low GL food. Conversely, a candy bar has a GL rating of 25 (GI rating of 62 x 40 g of sugar per serving / 100), which categorizes it as a high GL food. As you can see from this example, GL is likely the better and more accurate means for assessing and choosing foods containing carbohydrate. Table 2.5 provides the various GI and GL classifications. Appendix A provides the GI and GL ratings for several common foods (Foster-Powell et al., 2002). Table 2.5. Classifications for Glycemic Index and Glycemic Load High Medium Low Glycemic Index 70-100 55-69 0-55 Glycemic Load ≥ 20 11-19 ≤ 10 Protein Similar to carbohydrates, protein also plays an important role within the body. For example, protein is used to build and repair various bodily tissues, support numerous metabolic reactions as well as maintain proper pH and fluid balance. The AMDR for protein is 10-35% of total calories. Protein can be found in a variety of foods with the largest quantities being found in animal products (e.g., meat, poultry and dairy). Whole grains, beans, legumes, nuts and seeds are also good sources of protein.
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