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Importance of Water in the Human Body

Updated on July 22, 2013
Water is essential: it regulates body temperature, carries oxygen and nutrients to every cell in our body, maintains our blood volume and ensures the integrity of our cardiovascular (and every other!) system.
Water is essential: it regulates body temperature, carries oxygen and nutrients to every cell in our body, maintains our blood volume and ensures the integrity of our cardiovascular (and every other!) system. | Source

Water Supports All Human Body Functions

The human body cannot survive without enough water; in fact, we can only last about 100 hours, give or take, without it. Water helps us moisten food (through our saliva), digest food (through our gastric secretions), transport oxygen and nutrients to and from our cells (via our blood), discard waste (through our urine and stools), and dissipate heat (through sweat and our breath). Water is the principal component of our muscles and organs. Water makes up about sixty (60) percent of an adult human male's total body weight until after age 50, and approximately fifty (50) percent of an adult human female's body weight. After age 50, this drops to about fifty-six (56) percent in males and forty-seven percent in females. The reason for the difference in water content between men and women has to do with the difference in fat levels, while the drop in the elderly has to do with their replacing muscle mass with fat. Once allowance is made for the fat content, there is very little difference between men and women, old or young, from childhood on.

Symptoms of Dehydration

The following are just a few symptoms of possible dehydration:

  • Thirst
  • Dry or sticky mouth
  • Dry skin
  • Swollen tongue
  • Weakness, sleepiness, tiredness or exhaustion
  • Confusion
  • Fainting
  • Decreased urine output
  • Constipation
  • Headaches
  • Inability to sweat
  • Muscle cramps
  • Heart palpitations (a jumpy feeling, or a feeling that your heart is racing or pounding)

The color of your urine may also be an indicator of dehydration. Typically healthy urine is light in color and odorless. If your urine changes color to a deep yellow or yellow-orange, then you may be dehydrated.

Body Water Loss

Our bodies lose more water on a daily basis than any other essential nutrient. We lose water through our skin, by sweating when our body needs to shake off excess heat, but also by simple skin surface evaporation (a loss we do not really detect). We lose water when we pass urine. We lose water through our feces (stools). We even lose water when we breathe. Known as respiratory water loss, it is water that humidifies the air we breathe in (inhale) and that we then exhale as water vapor. Typically, a moderately active healthy adult at rest, with no stress, disease or illness, loses approximately 1,500 to 1,600 milliliters of water on a daily basis (or about 1.59 quarts per day). This water loss needs to be replenished on a daily basis in order to avoid dehydration.

Water and Fluid Intake

There are two ways we take fluids (water being chief among them) into our system: externally and internally. External intake means the fluids and foods we take into our bodies orally (or by IV, if we are in a coma or on a respirator or otherwise cannot feed ourselves). Internal intake is through our own metabolism's production of water.

Metabolic water is produced through the oxidation process of the food we consume. However, this process only gives us about eight (8) to ten (10) percent of our water requirement through metabolic water production.

Since the foods we eat were all once living organisms, food is an invaluable source of water for our bodies. The best source of water comes from fruits and vegetables with a high water content, as shown in the tables below.

High Water Content Fruits

Fruit
Water Content Percentage
Lemon
96 %
Red tomato
94 %
Watermelon
92 %
Strawberries
92 %
Grapefruit
91 %
This table lists five fruits with the highest percentage of water content, in proportion to their weight. For our body to function properly, we need to take in approximately two (2) quarts of water per day.

Dark Green Leafy Vegetables Help Satisfy Your Water Intake Needs

Romaine and other lettuce, kale, spinach, mustard greens, swiss chard, and other dark leafy greens are jam-packed with essential nutrients, especially water, dietary fiber, iron, vitamins, minerals, phytochemicals and anti-oxidants.
Romaine and other lettuce, kale, spinach, mustard greens, swiss chard, and other dark leafy greens are jam-packed with essential nutrients, especially water, dietary fiber, iron, vitamins, minerals, phytochemicals and anti-oxidants. | Source

High Water Content Vegetables

Vegetable
Water Content Percentage
Zucchini
97 %
Iceberg lettuce
96 %
Cucumber
96 %
Radish
95 %
This table lists the five vegetables with the highest water content, in proportion to their weight. Even the most basic green salad will help you maintain your water needs and avoid dehydration!

Recommended Daily Water Requirement

To restore water balance to your body and replace the fluids lost during normal day-to-day activities (and more during exercise), the recommended daily water or fluid intake is still the "eight-eight rule:" eight 8-ounce glasses of water a day. However, the exact amount needed really does vary by individual. Influencing factors include where you live (cold, temperate or tropical climate), how much you weigh, and how active you are. To get a slightly more accurate requirement you can use on-line calculators, such as Medindia's Daily Water Intake Calculator, or apps. Or else you can use the following formula, taken from myfooddiary.com: half an ounce of fluid intake per day, for every pound of body weight.

And don't worry about drinking too much; your kidneys will excrete any excess fluid, thereby regulating your body fluid levels.

Of course, if you have a chronic condition, such as diabetes, whereby your body retains too much fluid, or, conversely, has a hard time retaining the optimal or required level of fluids, you really must see your doctor to ensure achieving optimal water balance.

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  • everymom profile image
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    Anahi Pari-di-Monriva 2 years ago from Massachusetts

    Agreed, @poetryman6969: without water there is no life!

  • poetryman6969 profile image

    poetryman6969 2 years ago

    Water is life!

  • everymom profile image
    Author

    Anahi Pari-di-Monriva 3 years ago from Massachusetts

    Thank you, Elias, for reading and commenting on my article! I agree that water is even more necessary during the summer...and, unfortunately, many of us do not even notice our body's call for it! Luckily, summer is also the time when the vegetables and fruits highest in water are in season! Keep well!

  • Elias Zanetti profile image

    Elias Zanetti 3 years ago from Athens, Greece

    Interesting and informative hub. Especially during the summer water becomes even more necessary for the body. Hopefully except from drinking water there are also many fruits and vegetables that can help.

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