As part of his regular series on triathlon nutrition, Joel Enoch looks at the risk of hyponatraemia

In the 2005 great North Run four runners collapsed and died during the event. Following the competition, there were calls for runners to ‘drink more water’ to combat unseasonably hot conditions. Advice like this is understandable, but may add to the misconception that water is the best thing to drink and that more water is better.

Over the last few months I have been privileged to work with many people preparing for the Virgin London Marathon. I admire every single runner for taking on such a massive challenge, but have been surprised by the lack of awareness regarding how to stay hydrated during running and sport in general.

The last article in the current series looked at some of the reasons for the use of sports drinks containing carbohydrate and electrolytes. This time we look more closely at the need for electrolytes and the possible consequences of drinking too much water.

As stated in the last article, when we sweat we lose both fluid and salts (electrolytes). During prolonged exercise, drinking water alone can potentially result in the development of a condition called hyponatraemia or water intoxication. When drinking just water the concentration of sodium in an around the cell is reduced and the cell cannot function as it should. The symptoms of this include fatigue, irritability, dizziness, nausea or vomiting. Crucially, these are very similar to symptoms of dehydration. Often, therefore, athletes will assume dehydration is occurring, drink more water in an attempt to combat the problem, thereby exacerbating the severity of symptoms. This chain of events may be a factor in some sporting deaths during exercise in hot conditions.

Whatever level of athlete you are, you can take some simple steps to ensure you avoid the risk of developing hyponatraemia.

Firstly, you need to replace salts lost in sweat by drinking fluids that contain sodium. It may be that you are only doing a short amount of exercise such as an hour turbo training session or run so your requirement for extra carbohydrate, such as that found in a traditional sports drink, is reduced. In this case, a low-calorie hydration drink can provide the fluid and sodium required to ensure the concentration of fluid consumed is similar to that which surrounds the cells.

Secondly, you need to make sure you don’t over-drink. Over drinking, even of drinks containing electrolytes, can cause medical issues and increase the risk of stomach problems during sport. Therefore, rather than trying to match sweat and urine loss during sport with fluid intake (up to 2 L an hour), you should try to limit your intake to around 200 ml of fluid every 15-20 min.  In most cases, this will be enough to limit the effects of dehydration, without causing other problems associated with overdrinking.

Whatever your sport, whatever your level, if you’re sweating, drink a hydration drink, rather than just water alone.

About Joel

Joel has competed in both European and World Championship Age-Group level triathlons. In 2009 he also raced Elite on two occasions and if it wasn’t for a dodgy zip on his tri suit he wouldn’t have done too badly! This year is his 3^rd ‘once in a lifetime opportunity’ to prove something on an international age-group level and he hopes to win some medals this time around! He has a BSc in Sports Science from Brunel University, an MSc in Nutrition from Bristol University and has been a Sport Scientist for the Lucozade Sport Science Team since the beginning of 2009. He works with both Olympic athletes and people who have never heard of carbohydrate!

Lucozde has recently launched a new low-calorie electrolyte drink, Lucozade Sport Lite

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How, when and why to use sports drinks

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