Overhydration: Are you drinking too much water?

Last week, we began discussing cellular ion concentrations. To exemplify the importance of these concentrations, Dr. Campisi explained how marathon runners can overhydrate, thus throwing off this fine balance between ions. But what exactly happens in the body physiologically when someone becomes overhydrated? And how much water is too much?

The physiological term for overhydration is hyponatremia, which means that sodium in the blood has become too diluted, due to the copious amounts of water ingested. More specifically, the decreased extracellular sodium shuts down the thirst center of the brain in addition to vasopressin secretion, resulting in excessive urine production. Symptoms include headache, lethargy, and nausea, and in severe cases, coma and death can result (Speedy 1999).

In 1999, researchers found that 18 percent of competitors in the New Zealand Ironman triathlon were hyponatremic (Speedy 1999). Overhydration is a very serious issue, and treatment isn’t simple. In order to restore the sodium levels back to normal, doctors must increase the sodium concentration, but at a slow enough pace so as not to cause a neurological injury (Sterns 2009). To prevent hyponatremia, marathoners are advised to drink enough water to keep their body weight after a race within two percent of their starting weight (Kuzma 2011). Some marathons have scales stationed every mile during the race to allow for fluid level monitoring (Engler 2003). However, this technique doesn’t take a person’s sweat rate or saltiness into account, plus body weight is not a good indication of hydration.

So while research is still being done to assess how to avoid hyponatremia in marathoners, the more important issue for non-marathoners is how to avoid dehydration. Some scientists say we should drink eight glasses of water a day, whereas others think we should listen to our bodies and drink when we’re feeling thirsty. It seems as though the latter view is more universally accepted today, and scientists have devised basic tips for measuring hydration levels. For example, you should wake up in the morning feeling hydrated. Urine in the morning should be clear or pale and remain that way throughout the day. Lastly, scientists advise people to drink a low-carb electrolyte drink or hot tea with salt and lemon in the afternoon to increase core temperature and help with fluid absorption (Kuzma 2011).

As shown, maintaining ion concentrations in the body is essential for the correct functioning of the brain and kidneys. Although major strides have been made to prevent marathoners from dying of hyponatremia, hopefully more discoveries are just around the corner.

References:

Engler N. 2003. Marathon Dilemma: How Much Water is Too Much? Reuters Health. The American Medical Athletic Association.

Kuzma C. 2011 Sep 12. Are You Drinking Too Much Water? Men’s Health News.

Speedy DB, Noakes TD, Rogers IR, Thompson JM, Campbell RG et al. 1999. Hyponatremia in ultradistance triathletes. Medicine and Science in Sports and Exercise. 31(6): 809-815.

Sterns RH, Nigwekar SU, Hix JK. 2009 May. The treatment of hyponatremia. Seminars n Nephrology. 29(3): 282-299.