Liquid and solid carbohydrates
Last reviewed: 15.05.2018
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The benefits of consuming carbohydrate-containing beverages during the load are generally recognized. But hardy athletes often consume high-carb foods, such as energy drinks, figs, homemade biscuits and fruits. Hard food empties the stomach more slowly than liquids, and protein and fat found in many high-carbohydrate foods can further delay the emptying of the stomach. Despite this, liquid and solid carbohydrate food is equally effective for increasing blood glucose levels and exercise performance.
Ingo et al. Evaluated metabolic effects of consumption of liquid carbohydrates, hard carbohydrates or in combination during a two-hour bicycle race at 70% V02max followed by a temporary test. The liquid was a 7% carbohydrate-electrolyte drink, and solid carbohydrates were represented by energy tiles, which gave 76% of calories from carbohydrates, 18% from proteins and 6% from fats. Each serving contained 0.4 g of carbohydrate-kg (an average of 28 g per serving and 54 grams per hour) and was consumed immediately before the load, and then every 30 minutes during the first 120 minutes of the load. The content of calories in these products was different, but they were isoenergetic for carbohydrates.
The presence of carbohydrates and indicators of time tests were the same if an equal amount of carbohydrates was consumed in the form of liquid, solid products or a combination thereof. Regardless of the shape of the carbohydrates, differences in blood glucose, insulin, or total oxidized carbohydrates for 120 min cycling at 70% V02max were not observed.
Robergs et al. [32] from the University of New Mejiko in Albuquerque compared the reactions of glucose in the blood and glucoregulatory hormones (insulin and glycagon) to the consumption of liquid and solid carbohydrate foods during a two-hour bicycle race at 65% V02max followed by a 30-minute maximum isokinetic drive. As a liquid, a 7% carbohydrate-electrolyte drink was used, and a solid carbohydrate was a briquette replacing food, which gave 67% of calories from carbohydrates, 10% from proteins and 23% from fats. Each serving provided 0.6 g carbohydrate-kg1 body weight per hour (on average 20 g per serving and 40 g per hour) and was absorbed at 0, 30, 60, 90 and 120 minutes of physical activity. Two tests were also conducted to study the glycemic reaction at rest. After consuming 75 g of liquid or solid carbohydrates, blood glucose and insulin levels were measured every 20 minutes for 2 hours.
Study of the glycemic reaction at rest has shown that with the same amount of absorbed carbohydrates, liquid carbohydrate food is more associated with insulin-dependent glucose than solid. This was due to the combination of proteins, fats and fibers in hard carbohydrates, which are known to delay gastric emptying and thus smooth out the insulin response to the given amount and type of carbohydrates in food. However, during a long cycling race, there was no difference in the effect of liquid and solid carbohydrate nutrition on blood glucose, glucoregulatory hormones, and exercise performance.
Each form of carbohydrates (liquid and solid) has its advantages [33]. Drinks for athletes and other liquids support the consumption of water necessary for stable hydration during exercise. Compared with liquids, high-carb products, energy tiles and gels are more convenient for transportation and provide both variety and saturation.
Consumption every 15-20 minutes of 150-300 ml (5-10 ounces) of sports drinks - Gatorade, Allsport and Powerade - provides enough carbohydrates. For example, consumption of 20 ounces per hour of a sports drink containing 6% carbohydrates gives 36 g carbohydrates and 8% 48 g carbohydrates. One banana (30 g), one energy cooker (47 g) or three large crackers from wholemeal flour (66 g), consumed every hour, also give an adequate amount of carbohydrates.
Specialists of the American College of Sports Medicine (ACSM) believe that the need for liquids and carbohydrates can be satisfied by taking 600-1200 ml per hour (20-40 ounces) of drinks containing 4-8% carbohydrates.
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