The adult male body is roughly 60 percent water while the female adult body is about 55 percent. Our blood is composed of 90 percent water; muscle is 75 percent, brain and heart are collectively 73 percent, our skin is 64 percent, and even our sturdy bones are watery at about 25 percent.
Water is an essential nutrient for every cell in our body and the maintenance of homeostasis (the stability of our internal little ecosystems). Water is required to digest food, transport nutrients to cells, regulate our body temperature (through respiration and sweating), lubricate our joints, absorb shocks for our brain and spinal cord, remove waste (via urination), regulate the acid-and-base balance, and enable our brains to produce hormones and neurotransmitters.
With all this work to do, it should be no wonder that, over the course of a lifetime, the average person will drink about 20,000 gallons of water.
How much?
The Dietary Reference Intake for water for adult men is 3.7 liters/day (15.5 cups). Adult women should aim for 2.7 liters/day (11.4 cups), unless she is pregnant, in which case she should drink closer to 3 liters (12.5 cups). Lactating women need to strive for even more, at about 3.8 liters/day (16 cups).
A dozen or so cups of water a day may seem like a lot, but the liquids you consume—tea, coffee, juice, as well as straight-up H20—count toward your total intake. Even the moisture in food (think watermelon and lettuce) can often constitute nearly a quarter of your daily water intake.
The guidelines for how much water you should be drinking are just that—rough guidelines. The actual amount of water that you need on any particular day should also take into consideration a range of dehydrating factors: your level of exercise, that day’s particular degree of heat and humidity, illness (especially if you’re losing fluid through vomiting and/or diarrhea), prescription drugs (some can leave you downright cotton-mouthed!), alcohol, diet (low calorie, high fiber, high protein, or high sodium diets require extra water), and airline travel.
A quick way to tell if you’re hydrated is to check your urine. If you have to go every two to four hours and the color is light yellow (vitamin supplements can alter the color of your urine), you should be well hydrated. A downloadable urine chart is available for you to check how well hydrated you really are.
Dehydration occurs when your total body water is low enough that your blood volume actually decreases, a result of either an insufficient intake or excessive losses of water. Mild dehydration—a body water loss of 1 to 2 percent—can impair physical and cognitive function. Symptoms include headache, fatigue, loss of appetite, dry mouth, and dark-colored urine. A 5 percent loss of body weight can cause nausea and difficulty concentrating, while a 10 to 20 percent loss can result in death.
While overhydration or water toxicity is rare, it can happen and usually involves illness, exercise, or a water-drinking contest. Long distance runners, too, are particularly at risk if they fail to supplement their hydration with an electrolyte replacement when exercising for over an hour. Early symptoms of water toxicity include nausea, muscle cramps, disorientation, slurred speech, and confusion. Water toxicity can result in seizure, coma, or death.
Bottled vs. tap
The standards for bottled water purity are comparable to the minimum standards set by the Environmental Protection Agency (EPA) for municipal water systems. Since the standard for bottled water is no stricter, bottled water can often simply be tap water in a bottle, though it must be labeled as so. “Distilled” and “purified” water are examples of treated municipal water. Carbonated water, seltzer, and tonic are considered soft drinks and are regulated as food, not water.
There are, however, regulations from the Food and Drug Administration (FDA) about the allowable levels of contaminants in bottled water; however, the FDA doesn’t have the capacity to undertake mandatory and widespread testing that the EPA does with public drinking water.
What other contaminants might be in your water?
If your house was built before 1986, it is likely you have lead pipes, fixtures, or solder. Brass or chrome-plated faucets and fixtures lead to the most significant amounts of lead into the water, especially hot water.
Arsenic contamination is frequently a problem for those who rely on well water. If you live in a city, improper disposal of pharmaceutical drugs may have contaminated your tap water. (Check out the EPA’s handy guide to “How to Dispose of Medicines Properly.”) If you live close to a farm or industrial site, your water should be tested for nitrates and chemicals.
Perfluorinated chemicals such as Perfluorooctanoic acid (PFOA) and Perfluroheptanoic acid (PFHPA) are a group of artificial chemicals used in hundreds of products like nonstick pans, stain repellent clothing, wire coating, and firefighting foam. These chemicals don’t break down in the environment and have been found in the drinking water of 15 million Americans in 27 states. They have been linked to endocrine disruption, cancer, accelerated puberty, and thyroid changes. Click here to find out what’s in your drinking water.
The good news is that there are water treatment systems that address all of these issues. Plus, at the cost of about 18 cents a gallon, it's a grand bargain compared to $2 (or more!) for an 8-12 oz bottle of water.
Ensuring sufficient, clean water intake
There are three types of water filters. The first is a carafe-type, activated carbon filter like PUR or Brita. While cost-efficient and ubiquitously available, these types often don’t filter out arsenic. The second type is a filter that screws onto the faucet, which, like the carafe-types, also uses carbon to filter out lead, mercury, pharmaceuticals, and chlorine. The other option is a multi-stage filtration system, such as an ion-exchange (“water softening”) technology or a reverse osmosis process that can tackle more complicated issues like arsenic. These filters can either be fitted under the sink or in the basement, next to the water heater.
If you find it difficult to drink the recommended amount of water every day, try mixing it up by adding fresh fruits and vegetables like lemon, limes, or cucumbers to your water (or any other fruit or veg that may appeal to you). Consume foods with plenty of water in them like oranges, kiwi, celery, tomatoes, cucumbers, yogurt, lentils, cooked rice, and soups. Keep a water bottle close by; having water within reach encourages frequent intake. If you’re drinking alcohol, have a big glass of water for every drink. Lastly, drink lots of water while flying and limit alcohol consumption on the flight.