Author(s)： Cássia Pegoretti, Adriane Elisabete Costa Antunes, Fúlvia de Barros Manchado-Gobatto, Caroline Dario Capitani
The hydration status of a physically active individual or athlete can influence his/her physical or mental performance. The degree of hypohydration may lead to serious health problems, and consequently to impair athletic performance. The consumption of water or carbohydrate-electrolyte beverages before, during and after exercise is essential to maintain fluid balance and prevent dehydration. Besides these drinks, research findings have pointed using bovine milk as an alternative to sports drinks to optimize hydration levels in athletes and physically active individuals. The nutritional composition of cow’s milk promotes post-exercise rehydration process, due to the natural presence of water and electrolytes such as sodium and potassium. Although most studies have confirmed that bovine milk is a viable alternative for rehydration, recent studies have not reported significant differences between milk and some sports drinks for hydration process. Thus, milk consumption could be used as an alternative beverage for the hydration process.
Physical activity results in loss of body water and electrolytes through sweating, which are essentials for regulating body temperature. The loss of 2% of body mass during exercise can cause a decrease in performance and can also compromise aerobic, cognitive and mental performance  . Therefore, adequate fluid intake during exercise is highly recommended. According to the American College of Sports Medicine (2007)  , pre-exercise hydration ensures euhydration and water balance, in order to subsequently ensure the goal to replace fluid and electrolyte looses. Thus, the consumption of carbohydrate-electrolyte beverages (sports drinks), especially during exercise, is better than water consumption to ensure the replacement of fluids and electrolytes  .
An alternative to available commercial sports drink is cow’s milk or drinks containing cow’s milk proteins, especially whey proteins, which has shown positive results in the post-exercise rehydration process, according to some referenced studies  - . These studies associate the hydration benefits with nutritional aspects of milk, namely natural electrolytes composition (sodium and potassium), presence of water, carbohydrates and proteins and longer gastric emptying time  –  .
As an alternative strategy to improve hydration during sporting activities, the aim of this work was to conduct a literature review about the use of milk as an option to replace the lost fluids during exercises.
Thus, a qualitative systematic review was conducted in international databases (PubMed, Science Direct, Scielo) between August and October 2014 using the keywords: hydration, dehydration, fluid replacement, bovine milk, milk proteins, athletic performance, and exercises, in order to synthesize qualitative evidence to address aspects other than effectiveness on sports beverage to hydration. The inclusion criteria considered articles published between 2006 and 2014.
These studies suggested that the use of milk in the post exercise can help to replace fluids and promote the hydration. Despite the benefits regarding the intake of milk in post-exercise, it should be pointed out that some individuals have hypolactasia/alactasia, allergy to milk proteins or some other intolerance that prevents its consumption. In this case, are recommended to ingest alternative drinks rather than milk-based drinks to restore the normal physiological hydration state in the post-exercise  . For individuals with hypolactasia diagnosis, may be prescribed the lactose-free milk  as an alternative. Lactose-free milk was described as good recovery drink when compared to water and sports drink  . However, there are no studies that compared the effects of this type of milk on post-exercise hydration.
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