Exercise - to drink or not to drink?
Izelle Theunissen, MRC News
Sometimes it takes time to make your point. After almost 20 years, other
experts have come to recognise that Prof. Tim Noakes was right after all.
Drinking too much water can do more harm than good to athletes doing prolonged
exercise. In fact it can be fatal!
To drink, or not to drink? According to Prof. Noakes, the answer to this
question is slightly different than the standard 'drink, drink and drink some
more' fare that is usually dished out to sports enthusiasts.
"There have been quite a few paradigm shifts in theories about water
ingestion during exercise," says Noakes, who directs the MRC's Exercise
Science and Sports Medicine Research Unit. "Before 1969, the standard
belief was that athletes shouldn't drink during exercise. They accomplished many
world records, with only a few problems - despite not drinking much by today's
standards," he continues.
This was changed by a study by two South African researchers (Wyndham and
Strydom) who maintained that too little water caused dehydration, causing the
body temperature to rise, leading ultimately to heat stroke. "But they
unfortunately neglected to say that it was the intensity of the exercise that
led to the rise in body temperature - not the lack of water," explains
Noakes.
Sports drinks
The 1970s saw the rise of the sports drink industry. People were told to
drink 1,2 litres of fluid per hour - this was later changed to 'drink as much as
possible'. Paradoxically, the more people were told to drink, the more problems
athletes were having in the marathons and ultra-marathons. Particularly women
athletes in North America were literally paying with their lives.
Noakes explains why: "These athletes were running the marathons at very
slow speed - contrary to the elite athletes, who would finish in 2-3 hours,
these runners were running times of 5-6 hours. This meant that they were
ingesting 1,2 litre of water, every hour, for up to 6 hours. This led to massive
over-hydration and our Unit was the first to report this problem in the Comrades
Marathon in 1985," he explains.
Hyponatraemia
Over-hydration is no joke. It causes the body - and brain - to swell. The
pressure of the brain against the skull increases, leading to convulsions, heart
failure and cessation of breathing.
Dr Tony Irving from Prof. Noakes' Unit then studied a group of 8 Comrades
runners who were hospitalised with hyponatraemia after the 1988 Comrades
Marathon. "We showed that, during recovery, they were passing out large
quantities of water. They didn't need any salt to make them better, so they
weren't salt deficient, but purely water overloaded," Noakes says.
This theory was scoffed at by experts from all over the world. Athletes were
still encouraged to drink as much as possible. But the Houston Marathon of 2000
changed at least one researcher's mind. Before the race, pamphlets were given
out that stated 'when you've drunk enough, you must drink some more'. Many
athletes landed into trouble and Dr Tamara Hew was in the medical tent when they
were admitted.
"Many of the athletes were unconscious when they were brought in, and
were given intravenous fluid immediately. But this only made them worse. So Dr
Hew decided to study runners in the next Houston Marathon. She was able to show
that there was a direct linear relationship between the amount of fluid these
ill athletes had consumed, and the severity of their hyponatraemia at the end of
the race. One lady who finished the race in desperate condition had managed to
drink more than 100 cups of fluid during the race as well as substantial amounts
of fluid the day before the race. Dr Hew has been working with us more recently
and Jonathan Dugas, a Texan currently studying for his Ph.D. in this Unit, will
be completing a joint study with Tamara's group at the 2003 Houston
Marathon," says Prof. Noakes.
More theories and experiments
Still the penny hadn't dropped, and the following year athletes were asked to
participate in an experiment - they were asked to drink as much as they could.
One group was given water and the other group a well-known American sports
drink. Predictably, it didn't make a difference to the result - runners who
overdrank were equally hyponatramic, whether they had water or the sports drink.
"The organisers of the Marathon finally got the message. So for next
year's race they will be halving the number of water stations on the course
during the race. But that did not stop the sports drink company producing an
advertisement in January 2002 stating that runners should drink 1,2 litres of
fluid per hour. This was followed by another advertisement in June 2002, which
said that you could drink up to 1,6 litres per hour during exercise,"
Noakes says.
Noakes then wrote a letter to the running magazine in which the advert was
featured, pointing out the dangers of this advice. But the magazine refused to
publish it because Noakes' view conflicted with those of one of their chief
sponsors.
About turn
Then suddenly, within a month, the same magazine ran a completely different
advert warning runners that they should not overdrink during exercise. "It
was the most remarkable change I have ever seen in my medical career - in less
than 30 days, the advice of how athletes should drink during exercise was
suddenly reversed", he laughs.
Prof. Tim Noakes recently received an award for this research at the
prestigious Prix Nationale 4th International Symposium of Water in Cannes. Nine
awards are given for excellent research, and Prof. Noakes bagged the prize in
the Medical Section.
Noakes believes that this has something to do with the death of an athlete
taking part in the Boston Marathon in April 2002. This was a women amateur
runner who, literally, had too much sports drink during the event. Then in
August, the Boston Globe and New York Times newspapers carried front page
reports of the autopsy findings in this case. The conclusion was that the young
lady had died because she had drunk too much Gatorade (sports drink) during the
race and that this had directly caused her death. "So sadly it has taken
all these years, with numerous deaths, to believe something that had been
proposed in 1985 and definitively proven by 1991," Noakes says.
Noakes has a very down-to-earth explanation for the over-hydration
phenomenon. "I believe that the body is adapted for conditions of mild
dehydration. We evolved from hunters - we had to run and chase animals on the
hot African plains. We didn't have time to pause for a drink! Physiologists who
did not understand either human's prehistory and the history of running then
came along with the unproven hypothesis that to become even the slightest bit
dehydrated during exercise would kill you. And then the sports drinks industry
in the United States used this bad, indeed non-existent science to market their
products."
More information:
For more advice about sports drinking matters, please contact Prof. Noakes at
tel.: (021) 650-4557 or
e-mail: noakes@iafrica.com.
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