Subtitles section Play video Print subtitles Water is amazing! It's necessary for life to exist, makes you healthier, and it's incredibly refreshing especially after an intense workout. But is water intoxication a real thing? Can you drink too much water? We're often told to drink around 8 glasses of water a day to stay healthy, but the honest truth is that this specific number is somewhat arbitrary, and no scientific research exists to support it. Regardless, we know water is incredibly important; in fact, every organism we know of requires water to survive. Not only does it help the human body to bring oxygen and nutrients to the cells, regulate body temperatures and aid metabolism, but it flushes waste out of the body. Sweat out too much during a sporting event, and you'll start to feel a bit woozy. Three days without water, and you likely won't survive. So how could such an essential substance hurt us? It all comes down to the cellular level. The water you drink has very few electrolytes in it - things like sodium or potassium - especially compared to your cells. The electrolytes in your cells allow your muscles and nerves to work properly, and help to control blood pressure and blood volume. Without them, your body cannot function. Now normally, the difference in the electrolyte concentration inside and outside the cell wouldn't pose a problem, because your kidneys flush out any excess water. However, the kidneys can only excrete fluid at a certain rate. This means that consuming a lot of water in a short period of time creates a large concentration difference. As a result, water is drawn into the cells in an attempt to dilute the concentration and even out the proportion of electrolytes, and this causes the cells to swell. The problem is, unlike other parts of your body, the brain literally has no room inside the skull for these newly plump cells. This results in extreme headaches and confusion, leading to seizures, comas, respiratory arrest and even death. So should you be worried? Not likely! Cases of water intoxication are very rare, though they do happen in extreme circumstances. Close to 1/6 of marathon runners develop mild cases in their careers, with all endurance athletes at a higher risk. This is because under the extremes of athletic stress, the body attempts to conserve water. So not only are you taking more water in, you're peeing less out. Science says, though you're not likely to suffer from water intoxication, you should drink to your thirst - it's the best indicator! Don't forget: we have a new video out every day during the Olympics. But if you can't wait, head to cbc.ca/olympics/ScienceSays for more. Keep asking those burning questions with the hashtag ScienceSays, and subscribe for more awesome science videos!