You’ve probably heard on several occasions that you’ll only be truly healthy if you guzzle eight glasses of water every day. While this health rule might not be completely true, it still makes an important point -- the human body simply cannot survive without water. According to “Nutrition and Diet Therapy: Evidence-Based Applications,” the human body can live for one month without food, but it can only survive for six days without water. Rather than relying on the outdated eight-glasses-per-day theory, consider your age, gender, health status, environment and lifestyle to determine proper daily fluid intake.
As with other nutrients, the Food and Nutrition Board recommends a specific daily water intake depending on age and gender. As a general rule, adult males need 3.7 liters of water per day, while adult women need 2.7 liters per day. However, pregnant women should aim for 3 liters per day, and lactating women need 3.8 liters per day. The daily adequate intake of water is lower before the age of 18. From birth to 12 months of age, infants need just 0.7 to 0.8 liters per day -- which is easily achieved through breast milk alone. The daily intake increases to 1.3 liters from age 1 to 3 and 1.7 liters from age 4 to 8. Males then need 2.4 to 3.3 liters per day until the age of 18, while females need just 2.1 to 2.3 liters per day until they reach adulthood.
Only 80 percent of your daily water intake needs to come from fluids. The remaining 20 percent can be obtained from the foods you eat. Fruits and veggies are the most fluid-filled foods, with some containing up to 90 percent water. Grains, meat, eggs and dairy products also contain a hefty dose of water. And pure water isn’t your only liquid choice to fulfill your fluid needs, as all beverages contribute to your daily intake. While milk, tea and juice might be your best non-water choices, even coffee and soda can help you meet your recommended intake.
8x8: Rule or Myth?
Drinking eight 8-ounce glasses of water every day would equate to a total of 64 fluid ounces, or roughly 1.9 liters of fluid. A 2009 Scientific American article suggests that the 8x8 rule was originally developed because the Food and Nutrition Board once suggested that people consume 1 milliliter of water for every calorie of food consumed, which equates to about 64 ounces on a 1,900-calorie-per-day diet. But while the 8x8 idea might not actually be based on scientific evidence, it’s not a bad rule to include in your lifestyle -- it's an easy way to remember to drink plenty of water throughout the day.
Although the Food and Nutrition Board’s adequate intake is a good rule to follow, it’s not foolproof. Your physician can help you determine your ideal daily fluid intake based on your lifestyle, environment and health status. Some people require a greater amount of fluid per day -- such as someone who frequently engages in vigorous exercise, people who live in a hot or humid climate and during an illness associated with fevers, vomiting or diarrhea. On the other hand, some people need less water per day, such as people with heart failure, kidney disease or liver disease.
- "Nutrition and Diet Therapy: Evidence-Based Applications;" Carroll Lutz and Karen Przytulski
- Food and Nutrition Board: Dietary Reference Intakes: Recommended Intakes for Individuals
- MayoClinic.com: Water: How Much Should You Drink Every Day?
- Scientific American: Fact or Fiction? You Must Drink 8 Glasses of Water Daily
- Centers for Disease Control and Prevention: Water: Meeting Your Daily Fluid Needs
- a glass of water image by Xuejun li from Fotolia.com