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The role of carbohydrates in sports nutrition
Last reviewed: 15.05.2018
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High-carbohydrate foods are classified as carbohydrates (simple and complex), carbohydrate (liquid and solid) or glycemic carbohydrate index (low, medium, high). Classification of carbohydrates by the type of "simple" or "complex", "liquid" or "solid" does not reflect the effect of food and liquids rich in carbohydrates on glucose and insulin levels in the blood, and the classification by the glycemic index reflects this influence.
Glycemic index is used to classify different types of food by measuring the blood glucose level after their adoption and comparing it with standard food, or glucose or white bread. This index is calculated from the increase in the blood glucose curve after taking a test meal that provides 50 g of carbohydrates, compared to a similar curve after absorbing the same amount of carbohydrates from standard food. All tests are performed on an empty stomach.
Food is divided into high glycemic (glucose, bread, potatoes, cereal for breakfast, drinks for athletes), medium-glycemic (sucrose, soft drinks, oats, tropical fruits: bananas and mangoes) or low-glycemic (fructose, milk, yogurt, lentils, fruit cool climate: apples and oranges). There are published international tables of glycemic indices for many types of products.
The glycemic index reflects the ability to digest and absorb food rich in carbohydrates. Thus, the shape of food (particle size, the presence of whole grains, the structure and viscosity), the degree of processing and cooking, the presence of fructose or lactose (both Glycemic index is low), the ratio of amylopectin and amylose in starch affects the digestion rate (amylose digestion rate is low ), the interaction of starch with protein or starch with fat, as well as the presence of phytins and lectins.
It is assumed that by manipulating glycemic indices of various foods and dishes, you can increase the amount of carbohydrates and improve athletic performance. For example, products with a low glycemic index can be recommended to use before exercise to maintain carbohydrate levels. Foods rich in carbohydrates with an average or high glycemic index can be recommended during exercise to ensure oxidation of carbohydrates, and after it - to replenish glycogen.
The concept of the glycemic index has limitations. This index is based on the same amount (50 g) of carbohydrates, and not on average. The available index values are also mainly based on tests using one type of product, so the response of blood glucose when consuming high-glycemic products can be smoothed when combined with low-glycemic foods in dishes. But mixed dishes can use a weighted average of the glycemic indices of carbohydrate-rich foods that make up this dish.
Glycemic index is useful to athletes for food choice. However, further research is needed. This index should not be used solely to determine the intake of carbohydrates and food before training, during and after. Food has other characteristics that are important for athletes, such as nutrition, taste, compactness, price, tolerance to the body and ease of preparation. Since the choice of food is specific to each individual and the type of training, athletes must choose food in accordance with their nutritional goals.