Nov 15, 2023
Study compares sodium & carb levels for effective rehydration

Inadequate fluid intake during sports can cause dehydration, impair performance, and increase the probability of heat sickness. Proper rehydration is critical between training sessions and tournaments, especially during brief recuperation periods.

Rehydration involves stomach emptying, intestinal fluid absorption, and fluid retention to replenish bodily fluid compartments.

rehydrationThe impact of varying sodium and carbohydrate content on rehydration beverages is unclear and requires further research.

A recent story from detailed a study comparing sodium and carbohydrate levels in sports drinks for effective rehydration. Below is an excerpt from the story.

The study aimed to assess the completeness of rehydration after 3.5 hours of beverage administration. The researchers compared water (W) as a placebo to an oral-rehydrating solution (45.0 mmol/L sodium and 2.5% carbohydrates) and a regular sports drink (18.0 mmol/L sodium and 6.0% carbohydrates). The team expected that rehydrating the ORS and SD would surpass the W.

The study included physically fit male individuals aged between 18 and 30 years who engaged regularly in moderate-strong exercise. Females were not included to evade the potential confounding influence of estrogen levels on the retention of water, which may influence rehydration comparisons in the testing duration. The study participants were healthy, without metabolic, cardiovascular, renal, or endocrine illness or malfunction, and followed a uniform diet. The peak oxygen intake was 50 mL/kg/minute.

Participants exercised during a 90-minute session consisting of three 25-minute periods of intermittent-intensity exercise performed indoors after a 2.0-minute warm-up. Sweat samples were collected during the second 25-minute phase of activity, and sodium concentration was determined to estimate whole-body sodium loss during exercise. No fluids were administered during the exercise-dehydration interval to achieve a 2.5% to 3.0% drop in body mass.

In total, 20 individuals participated in three trials performed over 3.5 hours. The ORS and SD had similar and higher %FR at 3.5 hours, with the ORS having increased suppression of urine production in the first 60 minutes compared to the W. By 3.5 hours, the ORS and SD promoted greater rehydration than the W, but the pattern of rehydration early in recovery favored the ORS.

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The water placebo showed more excretion of urine at the 30-minute timepoint than the SD trial, and at 60 minutes, it promoted more significant fluid loss compared to ORS and SD. By 135 minutes, W induced greater fluid loss compared to the ORS. The statistically significant interactions observed between 30- and 60-minute collections for SD versus the oral-rehydrating solution indicated that the ORS suppressed urine secretion to a greater extent than SD.

Overall, the study findings showed that beverages with higher sodium and lower cholesterol content promoted better rehydration completeness. The ORS and sports drinks rehydrated the athletes to a greater extent than the placebo. The ORS was 32% more effective than the water placebo, indicating that carbohydrates may offset the effects of lower sodium content. The ORS also promoted a more rapid recovery, as rapidly absorbed beverages with sodium and glucose osmolytes kept plasma osmolality higher and reduced urine excretion.

To read the full story from about the study, click here. 

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