Microsoft word - gssi statement for runners world-neth 7.28.05.doc
What is the true effect of drinking sports drinks and water on GI Complaints
Senior Scientist for Latin America and Europe
While controlled field studies like “The Effect of Two Sports Drinks and Water on GI
Complaints and Performance During an 18-km Run” are important to supplement the laboratory
findings of a variety of sports nutrition topics, this study by van Nieuwenhoven, Brouns and
Kovacs1 has a few important flaws.
This research study naturally leaves many facets of the issue uncovered but it also clearly
dismisses previous findings on this topic published by other groups working in the area of sports
nutrition. Additionally, the results visibly contradict prior research conducted by these authors2.
Any discussion on sports drinks should consider their broader qualities, together with as the role
of a properly formulated sports drink in promoting voluntary fluid intake to offset dehydration, as
well as in preventing the associated heat-related illnesses. Questionable Conclusions
Van Nieuwenhoven et al. should not dismiss previous results obtained in the laboratory,
especially when no support is provided for the potential mechanisms that may explain the
differences. If their own research in the laboratory has shown no differences in GI function in the
lab among exactly the same drinks (water, sports drink, and sports drink with caffeine), why
should there be any on the field?
While the authors attribute the discrepancy to the nature of the task and to the mental stress
resulting from the competition on the field, there is another important possibility: subjective
evaluation, used in the field study, is much more susceptible to bias. It is important to note that by
choosing to use mineral water instead of a water placebo (one in which the subjects would not be
able to tell apart the water from the sports drinks), the authors leave open the strong possibility
that these self-reported GI symptoms were influenced by a placebo effect, that is, to the
subjective perception of the participants that water is “cleaner and fresher” than any other
beverage. The fact that the questionnaire was filled out post-exercise, after the subjects had an
opportunity to drink ad libitum
of the test drink, exacerbates this problem.
It appears that the results of this study have been blown out of proportion. According to table 2, only two out of eleven
GI complaints evaluated showed a lower incidence with water than with
the sports drinks. None
of the eleven GI complaints showed a significantly lower intensity score
with water than with the sports drinks. It is not possible to know from this study how the GI
complaints would be when no drinking at all takes place. Finally, the study looked at performance
during running, presumable in a steady state, for about 90 minutes in a cool climate, a very
specific situation. There are many other field conditions where ingestion of sports drinks or
carbohydrate solutions has been shown to benefit athletes, such as intermittent, intense exercise
(think interval training)3 and prolonged cycling4.
Flaws in Study Design
In addition to the lack of a water placebo, other limitations of the article in question are related to
the study design. Fluid intake was small – much smaller than in many other published studies
(600 mL for the entire trial, or about 460 mL/h), and unlikely to challenge the gastrointestinal
. Since the level of dehydration reached at the end of the running protocols was not
assessed or reported, it is not possible to understand the role that drinking had in this study. There
is also the absence of a “no fluid” condition, which would allow for interesting comparisons on
the relative magnitude of the effects of drinking vs. the effects of different fluid compositions on
the GI symptoms. In addition, the amount of carbohydrate provided in the sports drinks was
relatively low (41.3 grams of carbohydrate total, or about 32 grams per hour). Since muscles can
use ingested carbohydrate as fuel at twice this rate, this was probably not the ideal amount to
improve performance. Van Nieuwenhoven Claims Not Supported by Recently Published Research
It is unfortunate that this study does not discuss some results published in the past five years,
most notoriously those by Plunkett & Hopkins in 19995 and Morton, Aragón-Vargas and Callister
(2004)6. Plunkett and Hopkins, studying the “side stitch” during a running protocol in the
laboratory, compared four different fluids, including water, and found the sports drink to be
better tolerated than water and the other beverages
The study by Morton and colleagues deserves further discussion because it was, like the van
Nieuwenhoven study, a running protocol where the subjects chose their own pace. The study
included a no-drink condition, and it used a water placebo (undistinguishable from the sports
drink) instead of plain water. Participants were questioned on GI symptoms while running. This is
the largest experimental study on exercise-related transient abdominal pain (ETAP, commonly
known as “side stitch”) to date. The study found no significant differences beween water placebo
and the sports drink in all but one GI symptom under study.
The researchers tested 40 stitch-prone, physically active subjects (fitness participants, not
athletes), who underwent a 23-minute treadmill running protocol. Participants completed 4
sessions each, according to a Latin-Square design for the order of the four trials: no fluid,
flavored water (FW, a water placebo with no carbohydrate, 48 mOsm/L), sports drink (SD,
Gatorade®, 6% carbohydrate and 295 mOsm/L), and reconstituted fruit juice (FJ, 10.4%
carbohydrate, 489 mOsm/L). A fifth session involved repeating the FJ trial, to measure reliability
of the instruments. The subjects were requested to consume an average of 1582 mL of fluid
(much more than they would normally need) during each 43-min testing session (20 minutes
before the run, and regularly during the run). Measures of "stitch" (ETAP), bloating, and other GI
disturbances were obtained.
ETAP was slightly more severe and frequent when drinking FW or SD than when no fluid
was used, but FJ was clearly worse. Most of the ETAP-related measures showed no
difference between FW and SD, but a clear disadvantage for the FJ
. The occurrence of ETAP
under all conditions is not surprising, as both the participants and the fluid volume were selected
to result in enough cases, to be able to make comparisons among beverages. A lower incidence of
ETAP and the other symptoms would be expected under normal fluid ingestion volumes.
Incidence of side-stitch, bloating, reflux and nausea was not significantly different between the
flavored water and the sports drink; only belching was higher in the sports drink than in the water
condition (98 vs. 88% of participants, compared with 15% when running was performed without
drinking any fluid). These results show that when runners cannot distinguish between a
sports drink and a water placebo, they rate their GI symptoms very similar under both
Sports Drinks for Runners: a Few Scientifically Proven Benefits
Minimizing dehydration is the simplest, yet most effective step athletes can take to protect both
health and performance during training and competition, especially in the heat. Sports drinks
offer several advantages over water for proper hydration, including better fluid retention thanks to
their sodium content7, better maintenance of plasma sodium8, and improved voluntary fluid
Sports drinks also provide carbohydrates. Carbohydrate intake during exercise has been shown to
improve performance during prolonged running and cycling at moderate intensity. Studies from
the past 20 years have also shown improvements during exercise lasting about one hour at higher
intensity, and during intermittent high intensity exercise, both in running and cycling activities10 References:
Van Nieuwenhoven M.A., Brouns F., and Kovacs E.M.R. (2005). The Effect of Two Sports Drinks and Water on GI Complaints and Performance During an 18-km Run. International Journal of Sports Medicine 26:281-285.
Van Nieuwenhoven M.A., Brummer R.-J.M., and Brouns F. (2000). Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine. Journal of Applied Physiology 89:1079-1085.
Welsh, R. S., J. M. Davis, J. R. Burke, and H. G. Williams. (2002). Carbohydrates and Physical/Mental Performance During Intermittent Exercise to Fatigue. Med Sci Sports Exerc 34(4): 723-31.
Coggan, A.R., and E.F. Coyle (1991). Carbohydrate ingestion during prolonged exercise: Effects on Metabolism and Performance. Exercise Sports Sciences Reviews 19: 1-40.
Plunkett B.T. and Hopkins W.G. (1999). Investigation of the side pain "stitch" induced by running after fluid ingestion. Medicine and Science in Sports and Exercise 31 (8):1169-1175.
Morton D.P., Aragón-Vargas L.F., and Callister R. (2004). Effect of Ingested Fluid Composition on Exercise-related Transient Abdominal Pain. International Journal of Sports Nutrition and Exercise Metabolism 14(2):197-208.
González-Alonso J, Heaps CL, and Coyle EF. (1992). Rehydration After Exercise With Common Beverages and Water. Int J Sports Med 13(5): 399-406.
Vrijens DM, and Rehrer NJ. (1999). Sodium-Free Fluid Ingestion Decreases Plasma Sodium During Exercise in the Heat. J Appl Physiol 86: 1847-51.
Passe, D. H., M. Horn, J. Stofan, and R. Murray. (2004). Palatability and Voluntary Intake of Sports Beverages, Diluted Orange Juice, and Water During Exercise. Int J Sport Nutr Exerc Metab 14(3): 272-84.
Aragón-Vargas L.F. (2001). Metabolic and Performance Responses to Carbohydrate Intake During Exercise. In Sports Drinks: Basic Science and Practical Aspects. Editors Maughan RJ, and Murray R, 153-82. Boca Raton, FL: CRC Press.
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