Drinking 8 to 10 glasses of water per day can provide significant health benefits such as reducing daytime fatigue, easing back and joint pain for 80% of sufferers, and decreasing the risk of cancer, including lowering the risk of colon cancer by 45% and breast cancer by 79%. Proper hydration is also important for brain function as even a 2% drop in body water can negatively impact short-term memory, math skills, and focus. While water intake has clear upside, drinking too much can also have strange side effects.