We hear it so often that we accept it without question—drink 8 glasses of 8 ounces each of water a day, or 8x8. But is this accurate and do we need this much?
It depends. According to Web MD, the Institute of Medicine advises that men need about 125 ounces of liquid daily and women 91 ounces. The first thing to note is that the liquid doesn't all have to be water. The second? Most of us are probably getting enough hydration if we eat an average diet from food and beverages. Did you know that an apple is 84% water, broccoli is 91%, and a plain bagel 33%?
Also, take note of what you're drinking—alcohol is dehydrating. Coffee and sodas are hydrating, but caffeine is a natural diuretic. Water is the best choice because it's free and calorie-free.
How much water you need in a day depends on a number of factors from your age to your gender, health, weight, activity level, and even the weather. If it's hot and you're perspiring--you probably need to drink more water. But you may also need more water in other extreme weather conditions such as when it's cold, humid, or you're at high altitude. Children need lots of liquid—they get dehydrated more easily than the rest of us and seniors may need to drink extra liquid because of health issues. Heavier people need more water also.
Can you drink too much water and does it matter?
It's uncommon, according to the Mayo Clinic, but if “your kidneys are unable to excrete the excess water, the electrolyte content of the blood is diluted, resulting in hyponatremia.” This mostly affects endurance athletes such as marathon runners and is rare in healthy adults who eat the average diet. But some health conditions including “heart failure and some types of kidney, liver and adrenal diseases may impair excretion of water and require that you limit your fluid intake.”
If you're exercising intensely (or for more than an hour), experts recommend sports drinks that contain sodium. “This also reduces the chances of hyponatremia, which can be life-threatening,” says the Mayo Clinic. For short periods of exercise or any activity that makes you perspire, drink an extra 1.5 to 2.5 glasses of water.
According to Web MD: Our kidneys process 20 to 1000 ml of fluid per hour. So it's not easy to go into fluid overload, but it can happen if you drink too much, too quickly. Symptoms include weight gain, nausea, and bloating and may reduce the sodium levels in your blood, “which can result in headaches, confusion, seizures, and coma.”
Can you lose weight by drinking water?
Studies show this to be true—when you drink before a meal it fills you up and you tend to eat less/fewer calories. However, longer-term studies need to be carried out, say the experts.
Is your body 60% water?
“Absolutely not,” says Dr. Eric Berg in the 8 Glasses of Water Per Day Lie, Your body is not really 60% water, as conventional wisdom would have us believe, but is 60% “electrolyte fluid. Water is just one component of these fluids, and your body constantly works to maintain the proper balance of water, electrolytes, and minerals in these fluids. Drinking significantly more water than you need does nothing but tax this function of the body.”
How much water should you drink?
Dr. Berg's recommendation is that you “drink when you're thirsty.” So it's not wrong if you're not consuming 64 ounces daily—your water intake is probably fine as long as you're not thirsty.”
Whether you monitor your water intake or are sure you're getting your liquids from your healthy diet, the bottom line is that water keeps your body and brain working. Without it your health would suffer—so if you're thirsty, drink up!
p.s. It varies, but in general, we can survive up to about three weeks without food, but only three days to a week without water.