Most of us have accepted that we need that amount in addition to any other beverages we were consuming. The truth of the matter is that there is nothing found in the research to back that belief.
Dr. Heinz Valtin of Dartmouth Medical School conducted a literature review to find the research behind the recommendation for eight ounces of water eight times per day.He never found it although he thinks he knows where the idea originated.
The Food and Nutrition Board of the National research Council has recommended “1 milliliter of water for each calorie of food”. One ounce of water is approximately 30 milliliters. If a person consumed around 2,000 calories per day, their need would be about 67 ounces of water per day based on this recommendation. That’s pretty close to the 64 ounce recommendation made by the “8 x 8” rule.
Total water intake includes water from the food we eat, water in beverages and drinking water. For men ages 19-30, the Adequate Intakes (AI) for water is 3.7 liters or the equivalent of about 15 cups; for women of the same age the AI is 2.7 liters or 11 cups. This turns out to be more than the eight cups we have always thought was the correct amount. Keep in mind that AIs are figured based on actual average intake of men and women who may have been drinking more than they actually need. Your need may be more or less. Another important thing to remember is this includes fluid from all sources including food.
If you always thought that the water in coffee, tea and soda didn’t count toward total fluid intake, you can rest assured that it does. You may have heard that caffeine in some of these drinks acts as a diuretic so it doesn’t count. For people who regularly drink beverages with caffeine, the diuretic effect is minimal so your body does benefit from the fluid. The food you eat supplies about 20 percent of the fluid eaten in a day.
The bottom line is that most people get enough water in the food and beverages they consume throughout the day. Just pay special attention on these hot summer days because having enough fluid in your body helps keep you cool.