Water has a very substantial responsibility within the body. Without water, bodily processes necessary for life would shut down in a matter of days. Water makes up the greatest component of the human body, comprising 50–70 percent of the body's weight. Interestingly, human beings can survive for up to eight weeks without food but only a couple of days without water.

Water has many jobs throughout the body. It acts as a lubricant all over the body — in joints and connective tissues and within organs and vessels — and it even lubricates the body's cells. It also provides electrolytes (sodium, calcium, and magnesium) to the body that are necessary for the balance of fluid compartments found throughout the body.

Water also contributes to temperature regulation, helps remove wastes from the body, and can even act as a shock absorber in some parts of the body.

Adults should drink approximately eight to twelve cups of water per day, maybe more if heavy sweating occurs. If you don't drink enough water your brain will let you know by telling you that you're thirsty. Once you have become thirsty, it usually means you have waited too long to intake water and you may already be dehydrated. It's best to drink water throughout the day to stay properly hydrated.