Water! How Much Do You Need?

Water is essential to good health and daily physiologically functions of the body (e.g., carries nutrients to cells; provides moist environment for the ears, nose, and throat). It makes up, on average, 60 percent of a body’s weight. A person’s water needs depend on factors such as health status and level of physical activity and even where one lives. Each day, body water (approximately 1 liter, a little less than 6 cups) is lost through the breath, perspiration, and bowel movements; and water is lost through urine with the average output for adults being about 1.5 liters (i.e., 6.3 cups). For the body to function properly, its water supply must be replenished by consumption of beverages and foods containing water. How much water is needed? It’s a simple question with no easy answer. Plain water is the best source for replenishing daily fluid needs.

Beverages such as milk, tea, coffee, low-sodium broth, soda, and fruit and vegetable juices also supply water. In addition, a healthy diet (lots of veggies and fruits) can make up about 20 percent of daily water intake. The highly promoted “8 x 8 ounce glasses of water daily” does not fit everyone equally. In fact, the 8 x 8 suggestion is not supported by scientific evidence. So, how much water should you drink each day?

How to gage how much to drink? The Institute of Medicine advises that men consume roughly 3 liters a day (about 13 cups) of total beverages and women consume 2.2 liters (about 9 cups) of total beverages a day. Even the 8 x 8 rule (approximately 1.9 liters) approach is adequate for many people. It is generally thought that it is not a good idea of using thirst alone as a guide for when to drink water. By the time one is thirsty, slight dehydration may have occurred. As a person gets older, the body is less able to sense dehydration and send signals to the brain that it is time to drink! Generally, researchers suggest that if you drink enough fluid so that you rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or slightly yellow urine a day, your fluid intake is probably adequate. (National Institutes of Health and Mayo Clinic)

Factors influencing water needs include exercise activity that causes sweating. This means water is lost and needs replenishing. Hot and humid weather causes most people to sweat. Higher altitudes (e.g., those greater than 8,200 feet) often cause more rapid breathing, which eliminates water from the body. Illnesses in which there is fever, vomiting and diarrhea cause loss of water. The “morning after the night before” of imbibing in too much alcohol leads to the sensation of thirst. More fluid has been excreted than what was taken in but alcohol also causes fluid inside the cells to move outside the cells (cellular dehydration). It takes time for the water to move back inside the cells.

Too much water? In contrast, illnesses that involve the kidneys, liver and adrenal glands may impair excretion. This means one should limit fluid intake. People should confer with their physicians to help gage the amount of needed water.

Side note: In case you have children or grandchildren who “go for” those “energy/power” or vitamin-laced bottles of water occupying grocery shelves. Check the labels for the list of ingredients. Most list sugar, high fructose corn syrup, and other sugars as the first ingredients. Calories! Calories! Calories! A person taking a multi-vitamin pill may ingest higher than necessary or healthful levels of vitamins and minerals. As for the so-called energy or power in the drink, it is caffeine and guarana, which is a strong caffeine substance.