# Osmolality of Components and Their Application in the Design of Functional Recovery Drinks
###### Abstract
Rehydration with large amounts of plain water may cause hyponatremia (i.e., low blood sodium) [7; 15; 16; 17], but not hypokalemia (i.e., low blood potassium) nor hypomagnesemia (i.e., low blood mag--magnesium). [PERSON] et al. 1992 [18] compared water absorption rates in a segment of the small intestine after perfusion with solutions of either isotonic sodium chloride or isotonic CHO-electrolyte (i.e., 8% sucrose and 16 mmol/L Na) and found that sodium chloride alone only marginally affected such rates, whereas CHO with sodium chloride increased the rates by around five-fold. Apart from sodium chloride, (and only in the presence of CHO), no other electrolytes affect water absorption [19]. Recent studies have shown that the CHO content is the most important factor affecting the rate of gastric emptying of rehydration drinks. CHO solutions at concentrations of >8 to 10% (w/v) significantly inhibit gastric emptying, thereby reducing fluid available for absorption, and should therefore not be used whenever there are sweat losses and the body's resulting fluid requirements are high. Regular soft drinks and fruit juices containing large amounts of CHO therefore cannot be used as functional rehydration drinks; for example, most fruit juices and soft drinks contain >100 g CHO/I. This is also the case for designer energy drinks where osmolalities range from 500 to 800 mOsm/kg H\({}_{2}\)O, which reduces rapid fluid uptake by the body. Studies [7; 19; 20; 21] on performance and fatigue recommend carbohydrate concentrations ranging from 60 to 80 g/L in rehydration drinks as providing optimal support for performance. Whenever fluid losses are relatively small, it is possible to increase a drink's CHO content to a maximum of 150 g/L if an optimal CHO supply of 30 to 60 g/h for performance support is the desired prime criterion. To this amount of CHO, sportspersons should then add appropriate amounts of water tailored to their individual needs and preferences. To keep the osmolality as low as possible, long-chain glucose polymers and/or maltodext are preferred because strongly hypertonic drinks will greatly increase secretion of fluid from the blood into the gut, thereby increasing the risk of gastrointestinal discomfort and diarrhea [7]. Sports drinks having a >8% CHO content may slow down gastric emptying and intestinal absorption during exercise compared to those with lower CHO concentrations. There appears to be no difference in rates of gastric emptying or fluid absorption between water and sports drinks when carbohydrate concentrations are between 4% and 8% [3]. Studies of CHO on sports performance and fatigue indicate that the minimum supply of CHO should be >20 g/h [7]. A study by [PERSON] et al. (2009) [12] demonstrated that a hypertonic 10% glucose-electrolyte solution of about 667 mOsm/kg was more effective in maintaining a state of euhydration after exercise-induced dehydration of about 1.9%body mass than a 2% glucose solution with an osmolity of about 193 mOsm/kg and a 0% glucose solution with an osmolality of about 79 mOsm/kg. The literature reflects the possible risks of compounds, including sugars, caffeine, glycerol, and vitamin B2 found in sports drinks and energy drinks ingested by athletes and synergistic or antagonistic interactions of components of sports drinks [22]. Regarding dental health and sport dietary drinks, this study related the dental decay to the consumption of sports drinks with low pH [11]. Some of these beverages have variogenic properties due to their sugar content. Furthermore, long-term exposure of the body to an excess of simple sugars is associated with the development of obesity, insulin resistance, and diabetes. In the case of caffeine, the literature underlines some adverse effects including nervousness, irritability, anxiety, and others. Concerning vitamin B2, one case report indicated suspected anaphylaxis after the intake of this ingredient as part of an energy drink.