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Nutrition > Theory to practice- Gut upsets in athletes: are there differences between water and sports drinks?
Theory to practice- Gut upsets in athletes: are there differences between water and sports drinks?
Issue: Volume 28 Number 3
Background
Over my many years of involvement in endurance training and competition, I have tried most sports drinks and gels, and have had all sorts of gut upsets ranging from burping to flatulence to diarrhoea. While never pleasant, particularly when racing, all endurance athletes and coaches know these things are a fact of life in endurance sports, where fluid and food intake often determines the success or failure of an athlete by maintaining fluid status and blood glucose levels. Research has consistently shown that gastrointestinal complaints are frequently experienced during running rather than cycling or swimming, probably due to the increased movement of the gut during running. However, what type of drink is best suited to athletes to prevent these gut upsets? A recent Dutch study investigated the effect of three different drinks on gastrointestinal complaints and performance during competitive running in a controlled field study.
Research
Ninety-eight well-trained subjects (90 males, eight females, age 41 ± 8 years) performed a competitive 18-kilometre run three times within eight days in moderate temperatures of around 21 oC. Three different drinks were compared in a random order: water, a commercially available sports drink containing carbohydrate and electrolytes, and the same sports drink with added 150 mg/litre caffeine. The incidence of gastrointestinal complaints and the effect of the drinks on performance were studied. Each subject consumed four 150ml drinks at the start, after 4.5 kilometres, 9 kilometres, and 13.5 kilometres of the run. Incidence and intensity of gastrointestinal complaints during the run were determined using a 10-point scale questionnaire.
Findings
There were no significant differences in performance among the three drinks. Running time for the 18 kilometre run were:
- water — 1hr 18min 3sec ± 8min 30sec
- sports drink — 1hr 18min 23sec ± 8min 47sec
- caffeine-sports drink — 1hr 18min 3sec ± 8min 42sec.
The use of carbohydrate-containing sports drinks led to higher incidences of all types of gastrointestinal complaints compared to water. Significant differences (p < 0.05) were reached for:
- flatulence incidence: water 17.9 per cent, sports drink 28.6 per cent, caffeine-sports drink 30.6 per cent
- reflux incidence: water 55.7 per cent, sports drink 78.6 per cent, caffeine-sports drink 72.5 per cent.
There were no significant differences in intensity of the gastrointestinal complaints. The addition of caffeine to the sports drink had no effect on gastrointestinal complaints compared to sports drink alone, but water alone had the lowest incidence of gastrointestinal upsets.
Coaches’ takeout
As we would expect, water had the lowest impact on gut upsets because of its lack of ingredients that may lead to reflux or flatulence. However, these results also suggest that the addition of caffeine to sports drinks has no negative effects on gut upsets during endurance performance more than an hour long, the time frame in which all previous research suggests fluid and carbohydrate intake is required to maintain performance. Indeed, research suggests that the addition of caffeine in amounts of 1.5mg/kg acts as a performance enhancer during prolonged exercise.
Reference
van Nieuwenhoven, A, Brouns, F and Kovacs, MR 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(4), pp. 281–5.
