Do You Really Need to Drink 8 Glasses of Water a Day?

For years now, the conventional wisdom has been to drink eight glasses of water a day if you want to maintain good health. But is that really true? According to Heinz Valtin, MD, a retired professor of physiology from Dartmouth Medical School, the answer is no. 

In a study of peer-reviewed documents Dr. Valtin made several years ago, he find no scientific evidence supporting the claim that healthy people need to guzzle eight glasses of water a day, known as 8 x 8 (for eight, eight-ounce glasses). Other scientific reviews of the evidence came to similar conclusions.

So why has this myth been perpetuated for so long? According to Dr. Valtin, the 8 x 8 notion may have started in 1945 when the Food and Nutrition Board of National Research Council recommended that people consume approximately "one milliliter of water for each calorie of food," about two to two-and-a-half quarts per day (64 to 80 ounces). Although many people failed to take notice that much of that daily need for water could be met by the water content found in food.

The Health Benefits of Water

So how much water should you drink every day? That answer depends on a variety of factors including your health, your level of physical activity, the climate you live in, and whether you are pregnant or breastfeeding, according to the Mayo Clinic. Water is your body's principal chemical component and makes up about 60 percent of your body weight and every system in your body depends on it. Water flushes toxins out of your vital organs, carries nutrients to your cells and provides a moist environment for your ear, nose, and throat tissues. When your body doesn't get enough water to carry out its normal functions, you can become dehydrated, which can make you feel tired.

Each day, your body loses water through your breath, perspiration, urine, and bowel movements. To keep your body functioning at a high level, you must replenish its water supply by consuming enough beverages and foods that contain water.

Generally, you'll know that you consumed enough fluids from foods and beverages if you rarely feel thirsty, and if you eliminated 1.5 liters (6.3 cups) or more of colorless or slightly yellow urine a day. Drinking eight glasses or more of fluids a day is appropriate for people suffering from certain diseases, such as kidney stones, or for those participating in strenuous physical activity, taking long airplane flights, or living in hot climates. For everyone else, consuming less than eight glasses of fluids a day is adequate. Check with your doctor or dietician to help you determine how much water is best for you.




Scientific American
Fact of Fiction? You Must Drink 8 Glasses of Water Daily: Do healthy people really need liquids even when they are not thirsty?

Science Daily
"Drink At Least 8 Glasses of Water A Day"-Really?

Mayo Clinic
Nutrition and healthy eating
Water: How much should you drink every day?