Is too much water a bad thing?

I forgot to share what my secret weapon was at work when I forgot Advil last Wednesday. Cold water. I realized that if I drank cold water, it momentarily relieved the discomfort and pain associated with this damn retainer. So I drank lots and lots of water. I managed to down NINE 32-oz Nalgenes of water during work alone. Add another Nalgene during yoga on Wednesday night, and probably a half more once I got home. That adds up to roughly 336 oz of water on Wednesday. The "recommended" amount of water per day is 8 cups or 64 oz. I definitely exceeded that level. When I mentioned this to one of my rowing friends last week, she brought up the fact that too much water is a bad thing. I remembered hearing about something years and years ago where some high school football player died from drinking too much water during a strenuous practice, so I decided to look it up.

Let's break it down into the mechanics behind this issue. We have to start at the cellular level. The membranes of your cells are made up of phospholipids, forming a lipid bilayer. The heads of the phosopholipids are hydrophilic, while the tails are hydrophobic, so the heads face the inner and outer edges of the cell membrane. These semi-permeable membranes allow certain things like water molecules to pass through the membrane. Hello, osmosis:

See here for the source image.

This permeability allows the cell to exist in balance with its surroundings. But when you flood your body with water, the concentration of electrolytes and sodium in the blood outside of the cells decreases, causing the cell and blood concentrations to be unbalanced. In order to correct this imbalance, water enters the cell via osmosis, thus causing the cell to swell. See the hypotonic image below.

This cell swelling happens throughout the body, and you'll notice the side effects of the intracranial pressure (swelling in the brain). Some of these signs of "water intoxication" are: headache, confusion and dulled perception, drowsiness, as well as personality changes and irritability. You may also experience difficulty breathing during exertion, nausea/vomiting, thirst, and muscle weakness, twitching, or cramping. One example of a situation to be wary of is marathons. Marathon runners tend to consume a fair amount of water while running to stay hydrated, but they aren't eating a ton of food during these strenuous runs. This influx of water while doing an endurance sport can lead to hyponatremia, which is when the sodium ion concentration is lower than normal. This state can lead to collapse or confusion of the runners. That's why you can find tons of mid-run gels or snacks to help prevent hyponatremia. Some runners even use just salt tablets. Watch out for overexertion and heat stress as other contributing factors.

I looked up the LD50 of water and it is 90 g/kg (at least for rats). When I factor in my weight and do a brief conversion (thanks to Dr. Koros my Intro to Chemical Engineering Professor for training me how to do pretty conversions):

... you can see that my water intake was technically higher than the LD50 of water. You can also probably determine that I'm not dead. Otherwise, my ghost is really dedicated to blogging. But there are some big qualifiers here for why I didn't bite the big one last Wednesday... timing and the conditions. Sure if I had chugged 10 Nalgenes of water in one go, I might not have done so well, but considering that my water consumption was spread over 12 hours and that I was eating and consuming electrolytes and salts via my meals, it wasn't an issue. That being said, I don't recommend chugging that much water on a daily basis. Yes, water is good for you, but like with everything else... moderation is key. Drink when you're thirsty, eat when you're hungry, and maintain your balanced, healthy Paleo meals. Good luck!