The average person weighs 150lbs, so they should drink three quarts per day. A 200lb person should drink a full gallon per day. Athletes should drink even more than that. Follow these guidelines and you’ve adopted one of the most crucial health habits.

Our bodies are mostly water, and so this ongoing intake of water is essential to our every function. Drink the appropriate amounts, and everything is much more likely to function at optimal levels. Don’t drink enough water, and over the short term you will experience routine fatigue, dry skin, headaches and constipation; over the longer term, every body function will degrade more quickly. It really is as simple as that.

Things get a bit more complicated in what type of water to drink. Bottled spring water and filtered water are both good options. Do not drink tap water or distilled water.

The spring (not “drinking”) water should be bottled in clear polyethylene or glass containers, not the one-gallon plastic (PVC) containers that transfer far too many chemicals into the water. Filtered water can be obtained through low-cost filters, such as those provided by Brita or PUR brands. Another recommendation of mine is the GE Smart Water, which was top rated in Consumer Reports December 2002.

Tap water should be avoided because it contains chlorine and may contain fluoride, toxic substances that, with ongoing consumption, can have dire consequences for the body. Distilled water should also be avoided because it has the wrong ionization, pH, polarization and oxidation potentials, and can drain your body of necessary minerals. It has been tied to hair loss, which is often associated with certain mineral deficiencies.

Finally, drink water at room temperature if possible, as ice-cold water can harm the delicate lining of your stomach.