Hyponatremia
While dehydration can be dangerous, the danger from Hyponatremia is far greater. Hyponatremia is where the sodium (salt) levels in the blood becomes too dilute.
Contents
1 Symptoms
Initial symptoms tend to be a gain in weight and a general swelling and 'puffiness', most noticeable in the hands. More severe symptoms are caused by a swelling of the brain (cerebral edema) including nausea, vomiting, headache and malaise [1].
2 Causes
The cause of Hyponatremia is poorly understood, but commonly believed to be related to excessive water intake [2]. However, I would argue that Hyponatremia is caused excessive fluid intake in the absence of sufficient electrolytes. Hyponatremia can be common in endurance athletes:
- In a 1997 Ironman triathlon, almost 4% of competitors received attention for Hyponatremia [3].
- In a study of the 2002 Boston Marathon, 13% of finishers had some level of Hyponatremia, and 0.6% had critical Hyponatremia [4].
3 Risk Factors
The study revealed that the risk factors for Hyponatremia include
- A slow finish time (>4 hour)
- Consumption of >6 pints (3 liters) of water during the race
- BAA suggests a 'slight build' is also a risk factor[5].
Healthy kidneys can excrete about 2 pints (1 liter) of fluid per hour, but this may be reduced by exertion or illness [6]. So drinking >6 pints in 4 hours could easily exceed the kidneys capacity to cope. The recent rise in Hyponatremia may be due to earlier advice to athletes to "drink as much as possible" [7], combined with a general concern about salt intake.
4 References
- ↑ Hyponatremia http://en.wikipedia.org/wiki/Hyponatremia
- ↑ Exercise-Associated Hyponatremia http://cjasn.asnjournals.org/cgi/content/abstract/2/1/151
- ↑ Micronutrient Information Center - Sodium http://lpi.oregonstate.edu/infocenter/minerals/sodium/
- ↑ Hyponatremia among Runners in the Boston Marathon http://content.nejm.org/cgi/content/abstract/352/15/1550
- ↑ BAA - HYDRATION, DEHYDRATION AND HYPONATREMIA http://www.bostonmarathon.org/BostonMarathon/WelcomeBooklet.asp#hydration
- ↑ Water Intoxication http://en.wikipedia.org/wiki/Water_intoxication
- ↑ USATF Announces Major Changes in Hydration Guidelines for Long Distance Runners http://www.rrm.com/archive03/042803n2.htm
