Let's start with a couple of quiz questions. Put your hands up if you have given the following pieces of advice to your patients/athletes. (1) Thirst is not a good indicator of hydration. You must drink lots of fluids before, during and after exercise. (2) The optimum diet for weight control, general health and athletic performance consists of low fat, high carbohydrate.

Well, both my hands are up, and I suspect I am in good company among sports medicine professionals. For the past 30 years, these have been two of the basic tenets of sports nutrition. Recently, however, both these universally regarded ‘truths’ have been challenged.

MYTHBUSTERS #1

We now know that excessive intake of fluid during endurance events can lead to exercise-associated hyponatraemic encephalopathy (EAHE) or ‘water intoxication’.1 There have been a number of deaths reported from this syndrome. One of the researchers who has been prominent in researching this topic is Professor Tim Noakes from the University of Cape Town. In his recent book ‘Waterlogged’,2 Noakes explains how drinking too much water can lead to fluid retention and EAHE in those who also have the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Endurance athletes have been encouraged for the past three decades to not wait until they were thirsty, but to drink large amounts of water or sports drinks to prevent dehydration and heat illness. Noakes advises that excessive fluid overload is the major danger in endurance exercise, not …