Effect of beverage glucose and sodium content on fluid delivery, Jeukendrup et al, 2009

Background

Rapid fluid delivery from ingested beverages is the goal of oral rehydration solutions (ORS) and sports drinks.

Objective

The aim of the present study was to investigate the effects of increasing carbohydrate and sodium content upon fluid delivery using a deuterium oxide (D2O) tracer.

Design

Twenty healthy male subjects were divided into two groups of 10, the first group was a carbohydrate group (CHO) and the second a sodium group (Na). The CHO group ingested four different drinks with a stepped increase of 3% glucose from 0% to 9% while sodium concentration was 20 mmol/L. The Na group ingested four drinks with a stepped increase of 20 mmol/L from 0 mmol/L to 60 mmol/l while glucose concentration was 6%. All beverages contained 3 g of D2O. Subjects remained seated for two hours after ingestion of the experimental beverage, with blood taken every 5 min in the first hour and every 10 min in the second hour.

Results

Including 3% glucose in the beverage led to a significantly greater AUC 60 min (19640 ± 1252 δ‰ vs. VSMOW.60 min) than all trials. No carbohydrate (18381 ± 1198 δ‰ vs. VSMOW.60 min) had a greater AUC 60 min than a 6% (16088 ± 1359 δ‰ vs. VSMOW.60 min) and 9% beverage (13134 ± 1115 δ‰ vs. VSMOW.60 min); the 6% beverage had a significantly greater AUC 60 min than the 9% beverage. There was no difference in fluid delivery between the different sodium beverages.

Conclusion

In conclusion the present study showed that when carbohydrate concentration in an ingested beverage was increased above 6% fluid delivery was compromised. However, increasing the amount of sodium (0–60 mmol/L) in a 6% glucose beverage did not lead to increases in fluid delivery.

 

I came across this study when I looked up whether electrolyte powders / oral rehydration salts (ORS) without added glucose were effective. Wikipedia explains that this cannot be the case (bolding mine):

This study confirms that glucose is essential for absorbing the rehydration solution, but it seems that there are no advantages to adding more than 6% (weight/volume) and is in fact detrimental. In contrast, the WHO’s reduced osmolarity ORS formula, which NormaLyte uses, contains 13.5 g/L of glucose. Perhaps this should be lowered?

Edit: my calculation is wrong; see @Jonathan Edwards’ comment below.

 

That would be 1.35% W/V. Sounds OK?

 

I am always puzzled by these claims about rehydration. If I drink a pint of pure water I absorb it. I don't have watery diarrhoea, I have a pee after a bit - indicating it was absorbed.

Same happens with beer (more often) which I gather usually has no glucose and only 0.004% sodium.

 

My mistake. 6% glucose w/v is 6 g glucose per 100 mL of solution, not 1 L.

It seems to me that most of the research is oriented towards rehydrating athletes, that is, both retaining fluid and accelerating its delivery. At least, the latter is the focus of this review of the evidence base: Fate of ingested fluids: factors affecting gastric emptying and intestinal absorption of beverages in humans, Leiper, 2015

 

I can see that if you are running you would want absorption of fluid in upper small intestine rather than colon so maybe that is the rationale.