Intoxicated....with water?

Is it possible to drink too much water?

Actually, yes. “Water intoxication” from drinking too much plain water and not replacing electrolytes is possible..... and it’s happened to me.

Stop! That does not mean you should start limiting your fluid intake! Dehydration is still far more common than water intoxication. We just need to keep both in mind so that we avoid both extremes. Many times in nutrition counseling I think of the repeating mantra in "Goldilocks and the Three Bears"....we don't want too much, or too little....we want it just right......

With so much focus on avoiding dehydration, some cyclists can go a little overboard in their prevention efforts. When I say “some cyclists” I have to include myself in that group, as I have personal experience with drinking too much plain water and not replacing electrolytes on a 100-mile ride…..which led to water intoxication and hyponatremia. (Hyponatremia=low sodium concentration. Remember back to chemistry class and the periodic table? The symbol “Na” is for sodium. “Hypo” means low. So when you put it all together, you get the term “hyponatremia”.)

This basically means that by drinking only plain water (and LOT of it) that my blood supply also had too much plain water compared to the amount of electrolytes. A colleague once gave me this analogy to illustrate what’s going on in hyponatremia. Fill a glass with 1 cup of water and mix in 1 Tablespoon of salt (salt is half sodium). The concentration of salt in the glass is 1 Tablespoon per cup. Pour out half of the salt water. The water you pour out represents what you sweat out during exercise. The water left in the glass has ½ Tablespoon of salt. Add back ½ cup of plain water. The concentration of salt in the glass is now ½ Tablespoon per cup, which is only half of the concentration that was in the initial glass of salt water. So, if after sweating a lot you drink only plain water, a similar thing is going on in your bloodstream: The concentration of the sodium is less.

Severely low sodium is a concern because a normal sodium concentration is required for your body to conduct nerve impulses and for muscle function. Symptoms of hyponatremia include: nausea, muscle cramps, weakness, headache, disorientation. Unfortunately, the symptoms of hyponatremia can sometimes be misinterpreted as dehydration, and a cyclist may think he/she just needs to drink more water, possibly making the situation worse.

Hyponatremia is a risk primarily for endurance events such as marathons and all-day bike rides like the MS ride. You often hear warnings about hyponatremia around the time of the marathon each year. Hyponatremia is not really a concern for the elite runners who finish the course in 2 hours—they are running so darn fast and not drinking enough fluid to overwhelm their system. But for the non-elite-athlete-runners (the "slow-and-steady" folks like me) who may be on the course for 5 or more hours, if they only drink water and don’t include some sports drinks for electrolyte replacement, they can risk hyponatremia.

Hyponatremia is serious, but also very preventable. My main advice to you is to be sure to drink some sports drinks on the days of the MS ride and during long training days. A common recommendation is to have two bottles on your bike—one for water and one for sports drinks—and alternate drinking between the two.

In my next post, I’ll take you step-by-step through my day of mistakes that led to my own hyponatremic experience….and an unplanned visit to the hospital in Galena. It’s a tad embarrassing as a dietitian to show up in the ER with my electrolytes out of whack, but I certainly learned a lot from the experience. :o)

Looks like at last we may get a respite from the rain this weekend….Ride on!