The warning, made by sports medicine expert Dr Timothy Noakes in the current edition of the British Medical Journal, follows recent reports of a number of deaths from hyponatraemic encephalopathy – severe salt deficiencies in the blood caused by excessive drinking.

He explains that until the late 1960s, athletes were advised not to consume fluids during exercise sessions and competitions because it was thought to impair performance. However, the publication of an article in 1969, entitled “The danger of an inadequate water intake during marathon running”, lead to a change in guidelines on drinking during exercise.

But, Dr Noakes, from the Sports Science Institute of South Africa, says that this change in advice was not corroborated by scientific evidence, nor were any trials undertaken to assess whether the new guidelines were safe.

Shortly after the advice on fluid consumption during exercise changed, the first reports of hyponatraemic encephalopathy in athletes, military personnel and hikers began to appear.

However, Dr Noakes stresses that, now the condition is known about, further deaths from excessive fluid intake can easily be prevented. He adds that the safest and most effective advice is to only drink when personal thirst dictates – a fluid intake that would equate to between 400ml and 800ml per hour during most recreational and competitive exercise.

“The recent adoption of these guidelines by USA Track and Field provides the hope that this sad scientific aberration has finally run its tragic course,” Dr Noakes concludes.

© HMG Worldwide 2003
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