- In endurance exercise lasting for more than an hour, sports drinks can be beneficial over plain water because they can promote water absorption and retention, maintain physical performance and prevent water intoxication.
- The optimal content of sports drinks: sugar: 3-6 g/100 mL; sodium: 20-50 mmol/L (460-1,150 mg/L).
1) Stimulation of water absorption:
Sugar in sports drinks can increase the rate of water absorption by ~10%, but sugar content above 6% can slow down the delivery of water from the stomach into the small intestine and thus slow down the absorption (Nutrition & Metabolism, 2009 - Fig 1 - the blue line (G0) is water, G3, G6, G9 are sports drinks with diff % of glucose).
According to European Food Safety Authority (EFSA), 2011, sports drinks enhance water absorption during exercise, "which may be a beneficial physiological effect."
2) Improvement of water retention:
Sodium in sports drinks increases fluid retention in the body, which means it keeps water in your body for longer than plain water (International Journal of Sport Nutrition and Exercise Metabolism, 2017):
The purpose of this study was to examine the efficacy of water and a
50 mmol/L NaCl solution on postexercise rehydration when a standard
meal was consumed during rehydration. Eight healthy participants took
part in two experimental trials during which they lost 1.5 ± 0.4% of
initial body mass via intermittent exercise in the heat. Participants
then rehydrated over a 60-min period with water or a 50 mmol/L NaCl
solution in a volume equivalent to 150% of their body mass loss during
exercise. In addition, a standard meal was ingested during this time
which was equivalent to 30% of participants predicted daily energy
expenditure. Urine samples were collected before and after exercise
and for 3 hr after rehydration. Cumulative urine volume (981 ± 458 ml
and 577 ± 345 mL; p = .035) was greater, while percentage fluid
retained (50 and 70%) was lower during the water
compared with the NaCl trial respectively.
3) Prevention of water intoxication (dilutional hyponatremia):
Prolonged exercise (usually 4+ hours), like a marathon, during which participants drink 3+ liters of fluid with insufficient sodium content, can result in a drop of blood sodium, known as dilutional hyponatremia with brain edema, which can be life-threatening (NEJM, 2004). Sodium in sports drinks can prevent dilutional hyponatremia, but, the sodium content of some sports drinks is too low to prevent it. For example, in a 2002 Boston marathon, a 28-years-old woman has died due to hyponatremia after drinking a large amount of a sport drink during the race (Crossfit). To prevent hyponatremia, a sports drink should contain at least 20 mmol (460 mg) sodium per liter (5 mmol or 110 mg per 8 oz) (NSCA’s Guide to Sport and Exercise Nutrition).
4) Increased physical performance:
According to European Food Safety Authority (EFSA), 2011, sports drinks help to maintain endurance performance, but they do not reduce perceived effort during exercise.
In 2 small studies, drinking sports drinks was associated with increased physical performance:
a) In 7 cyclists pedaling for 2 hours in a hot environment (36 °C), Gatorade® and Powerade® preserved muscle power better (–3.1% and –3.8%) than plain water (–6%) (Applied Physiology, Nutrition and Metabolism, 2007).
b) 16 athletes were cycling for 80 minutes and then had a 10 km cycling trial. The time in a 10 km trial was better when they drank a sport drink (17.3 minutes) than when they drank water (17.8 minutes) (International Journal of Sport Nutrition and Exercise Metabolism).