15 August 2009

Why Gatorade May Not Rehydrate You Any Faster Than Water

Research Summary Critique

Reference: Jeukendrup AE, Currell K, Clarke J, Cole J, Blannin AK. Effect of beverage glucose and sodium content on fluid delivery. Nutr Metab (Lond) 2009;6:9. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=19232115

Purpose of study: The objective of many oral rehydration drinks is rapid fluid delivery to correct fluid balance in sports. This study investigated carbohydrate (CHO) and sodium (Na) effects on fluid delivery with a deuterium oxide (D20) tracer.

Previous research suggests Na concentration may increase delivery, but that CHO content is more important factor.

Type of study: Equivalence trial of eight different solutions.

Method used to conduct study: Two groups of 10 male subjects (ages 20 +- 1 y, weight: 81.2 +-7.5kg) were split into a CHO or NA group. The CHO group ingested four drinks, each with 20 mmol/L sodium, and with a stepped increase of 3% glucose from 0-9%. The Na group ingested four drinks, each with 6% glucose, with a stepped increase of 20 mmol/L from 0 mmol/L to 60 mmol/L. All drinks contained 3g of D20.

Each trial was performed in laboratory after overnight fast (7-9a.m.) and emptying of bladder. After ingesting drink, blood was taken every five minutes in the first hour and every 10 minutes in the second hour. Plasma D20 was analysed using isotope ratio mass spectrometry.

Summary: CHO concentration at 3% increased fluid delivery in comparison to 0%. Concentration above 6% led to fluid delivery that was slower than 0% and 3%. Sodium concentration in any amount did not show any increase in intestinal water absorption.

Critique: The researchers acknowledge that the investigation, which used the “triple lumen technique”, takes into account a section of the small intestine, but not gastric emptying. It may not represent total fluid availability in the body. However, D20 is useful to provide an integrative measure of gastric emptying and intestinal fluid absorption.

Nutritional implications and implications of future study: Because the study’s findings are that added sodium to oral rehydration drinks (sport drinks) has no effect on fluid delivery, it may change the way consumers choose these beverages. Sodium addition may not be preferred or it may still be for other reasons unrelated to fluid delivery such as for possible electrolyte replacement.

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