Supplement Science Series
Exploring some Caffeine Myths Part One:
Dehydration
Dehydration
By Veeraj Goyaram
Cape Town, South Africa
Cape Town, South Africa
"Coffee: the elixir of Life"
Let
me come straight to the point: In this article we will debunk a myth that
surrounds the use of caffeine from either coffee, its major food source, and
pure crystalline form. Caffeine is very often said to lead to dehydration in exercising individuals. We provide scientific evidence that these claims are false and that these
are invalid reasons why you shouldn't pop your caffeine tabs or even better,
drink your cup of coffee or before
training.
 |
| With compliments |
If Caffeine dehydrates at rest that doesn't mean the same thing happens during exercise
The earliest report of effect of caffeine on diuresis (water loss) comes from a study published in 1928 (Eddy and Downs, 1928) which, using a very small sample size of subjects, showed that caffeine ingestion induces an acute state of dehydration.
There is a major catch to this:
a) the subjects in which this was seen were not exercising but rather at rest. Consuming caffeine at rest and under exercise are two different scenarios. We cannot extrapolate what has been found in resting individuals to what may be happening under exercise.
b) The status of hydration of the individual when he/ she consumes caffeine affects whether he/ she will lose water. Most of the published studies didn't take this into consideration. This means that a subject who is taking caffeine may not lose water if adequately hydrated.
In the following section I will summarise some scientific studies done on the topic of water loss and caffeine using exercising individuals:
Study A: Treadmill walking with a backpack: No effect!
Subjects were given 5mg/kg caffeine 2hrs before exercise and 2.5mg/kg 30 mins before exercise and were asked to walk on a treadmill with a 22kg backpack in a thermoneutral (neither hot nor cold) environment. The scientists (Falk et al., ) did not see any difference in water loss between the caffeine and no caffeine groups. Since the research was done in thermoneutral environment further research looked at the effects of caffeine under more stressful conditions
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| Waterlogged: The Bible of Hydration Guidelines for sports By Professor Tim Noakes of the University of Cape Town Prof. Noakes is my head professor at the ESSM Research Unit Click to purchase on amazon.com |
Study B: Again, diuresis only at rest, not during exercise.
In a study by researchers from Ohio State University (Wemple et al., 1997), subjects were given 8.7mg/kg of caffeine (that's a hell of a lot) in divided doses and were asked to either cycle for 180 minutes at moderate intensity or remain rested. The results are interesting: an increase in urine volume was noted at rest whereas no significant effect in fluid balance was seen during exercise. This means that during exercise, the subjects consuming caffeine were not losing water any more than if they those who cycled without caffeine, even through sweating.
"A lot of the research between 1970 and 1990 that reported water and electrolyte loss by caffeine consumption used samples taken at rest rather than during exercise. We now know that the diuretic effect is indeed present during rest. People might have severely been misled"
In a study by researchers from Ohio State University (Wemple et al., 1997), subjects were given 8.7mg/kg of caffeine (that's a hell of a lot) in divided doses and were asked to either cycle for 180 minutes at moderate intensity or remain rested. The results are interesting: an increase in urine volume was noted at rest whereas no significant effect in fluid balance was seen during exercise. This means that during exercise, the subjects consuming caffeine were not losing water any more than if they those who cycled without caffeine, even through sweating.
"A lot of the research between 1970 and 1990 that reported water and electrolyte loss by caffeine consumption used samples taken at rest rather than during exercise. We now know that the diuretic effect is indeed present during rest. People might have severely been misled"
 |
| Caffeine improves rather than impairs performance |
In
this study by Fiala et al. (199) athletes exercising in the heat were asked to
rehydrate themselves using either Caffeinated or caffeine-free drink (they in
fact used Coca Cola at 7 cans a day or 740mg/ day of caffeine). The caffeine
athletes didn't experience any change in plasma volume (a measure of hydration
status), sweat rate, heart rate and body temperature. Interesting stuff,
indeed!
"The scientific literature does not support caffeine-induced diuresis during exercise. In fact, several studies have failed to show any change in sweat rate, total water loss, or negative change in fluid balance that would adversely affect performance, even under conditions of heat stress"
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| Caffeine is a great preworkout. The strength of pre-workout supplements in fact comes from caffeine! |
- There may be an argument for caffeine-induced water loss at rest
- Scientific literature does not show any negative effect of caffeine on water loss that could negatively impact on performance.
- Enjoy your caffeine or coffee but moderation is always the key. Consult your doctor if you have any heart condition.
- If you feel jittery from caffeine ingestion before a workout this indicates that you are sensitive to the stuff. Adjust your intake accordingly.
Related article: Caffeine as a recovery aid
References
Eddy
NM, Downs AW: Tolerance and cross-tolerance in the human subject to the
diruetic effect of caffeine, theobromine and theophylline. J Pharmacol Exp
Therap 1928, 33:167-174.
Falk B, Burstein R, Rosenblum J, Shaprio Y, Zylber-Katz E, Bashan N: Effects of caffeine ingestion on body fluid balance and thermoregulation during exercise. Can J Physiol Pharmacol 1990, 68:889-92.
Fiala KA, Casa DJ, Roti MW: Rehydration with a caffeinated beverage during the nonexercise periods of 3 consecutive days of 2-a-day practices. Int J of Sport Nutr Exerc Meta 2004, 14:419-29.
Wemple
RD, Lamb DR, McKeever KH: Caffeine vs caffeine-free sports drinks: Effects of
urine production at rest and during prolonged exercise. Int J of Sports Med
1997, 18:40-46.
©,2013, Veeraj Goyaram, Bodybuilding Mauritius. Any reprinting in any type of media is prohibited.
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