Why water is our most essential nutrient

What would we do without water – nothing!  Out of the six classes of nutrients (water, carbohydrates, protein, fat, vitamins and minerals) water is undoubtedly the most important nutrient of all.  Our bodies cannot store water or make it on its own and each day it must be replaced as we constantly lose water through our urine, feces, sweat, skin and lungs.  Most of us could go for weeks without eating food but would last only a few days without water. 


During this time of year as the temperatures rise and we become more conscious of our water intake, it’s a good idea to learn about what makes water so vital and why it is a nutrient we can’t live without.

Water within the human body

·         Newborn babies have the most water, with 78% of their weight composed of it.

·         Water makes up approximately 60% of an adult man’s weight and 55% of an adult woman’s weight.

·         People with more muscle mass have proportionately more water as muscle tissue is nearly three-fourths water by weight, whereas fat tissue is only about 10 percent water.

·         The human brain is 75% water.

Functions of water

·         Carries nutrients throughout the body.

·         Cleanses the blood of waste.

·         Necessary for many chemical reactions.

·         Helps maintain the body’s temperature through sweating

·         Aids digestion

·         Prevents constipation

·         Provides saliva to moisten food and makes swallowing possible

·         Lubricates joints to move smoothly

·         Acts as a shock absorber in the eyes, spinal cord and in the amniotic fluid that cushions the fetus during pregnancy.

Water needs by age

It’s difficult to be exact on how much water each individual needs as it depends a lot on of different factors such as activity level, temperature and humidity level, age, altitude, medications and diseases that can disturb water balance such as diabetes and kidney disease.

Here are approximate adequate daily intakes of fluid in general for men and women (includes water, milk, and other fluids):

·         Women – ages 19 and up – 1.9 liters or 8 cups

·         Men – ages 19 and up – 2.6 liters or 10 cups

Maintaining water balance

Everyday most of us probably don’t give much thought to water’s importance.  By drinking various fluids and from foods that provide us with water  - fruits and vegetables primarily – it all helps to maintain the balance of our water content with the amount of water we lose each day. 

But if this water balance is disturbed, it can lead to a life-threatening situation.  There are two ways our water balance gets out-of-balance – dehydration and water intoxication.

*Dehydration – This is simply a loss of water.  Some of us may have been dehydrated enough to land us in the hospital while many more of us are walking around chronically mildly dehydrated.  Dehydration can be brought about by diarrhea, vomiting, fever, excessive sweating, increased urination and not drinking enough fluids. 

The first sign of dehydration is thirst.  To ignore this symptom is to invite dehydration.  Signs of mild to moderate dehydration include:

*Increased thirst

*Dry mouth

*Tired or sleepy

*Decreased urine output and urine looks darker – it should be light or straw colored


*Dry skin


*Few or no tears

Signs of severe dehydration that needs medical attention right away include:

*Severely decreased urine output, more concentrated and a deep yellow or amber color

*Dizziness that doesn’t allow a person to stand or walk normally

*Low blood pressure

*Rapid heart rate


*Poor skin elasticity

*Lethargy, confusion or coma


Be aware of these symptoms and drink more fluids at the first sign of becoming thirsty.  Be aware that babies and children along with the elderly are often susceptible to dehydration.  Babies and children are particularly vulnerable when they are sick and are running a fever or experiencing diarrhea or vomiting.  The elderly are often at risk due to medications, not feeling thirsty, chronic illness and changes in kidney function.

*Water Intoxication- This is a rare yet dangerous dilution of the body’s fluids resulting from excessive ingestion of water or if the body is unable to get rid of excessive water by retaining it.  It is also known as hyponatremia as it throws off the balance between water and sodium by diluting sodium in the blood.

Signs of water intoxication include:

*Nausea and vomiting


*Confusion or disorientation

If left untreated, it can lead to more dangerous signs of:

*Muscle weakness, spasms or cramps




To avoid water intoxication drink no more than one liter or 4 cups per hour of fluid.  Endurance athletes are more likely to develop this, as they are concerned with becoming dehydrated, so it is recommended for them to drink sports beverages that contain electrolytes of sodium and potassium to replace what is being lost in sweat.  If you have a medical condition where fluid is retained such as diabetes, congestive heart failure or kidney problems, discuss with your doctor on how to treat this. 

Sources of water

Of course our source of water comes from either tap or bottled water or from other fluids that contain water such as coffee, juice, tea, milk, soup and soft drinks.  Even foods can provide some of our water needs mainly from fruits and vegetables. 

The majority of our water needs should come from drinking just water as it has no calories and will keep the body hydrated and in balance the best. 

Fluoridation of water

The addition of the mineral fluoride to the public water supply has been widely used in the United States since the 1950’s.  Its purpose is to reduce tooth decay and for preventing cavities.  Currently approximately 70% of public water supplies in the United States are fluoridated.  There are strong opinions both pro and con on the use of fluoride in the public water system.  Whatever your opinion may be, it is best to be informed on knowing whether your water supply is fluoridated or not, what the level of fluoridation is and to discuss this with your dentist for their opinion.  If you only consume water from bottled water, know that most bottled waters are not fluoridated but check the label or contact the bottling company for more information.




Cheryl Mussatto has over 30 years of experience as a Registered Dietitian and has worked in a variety of settings that cover a wide span of nutrition experience.  Currently she works as an adjunct professor for two community colleges, Allen Community College in Burlingame and Butler Community College in Council Grove, Kansas teaching two courses, Basic Nutrition and Therapeutic Nutrition. Cheryl also is a contributing author for osagecountyonline.com, an online newspaper and Edietitians, a global free nutritional and health magazine. Her articles for both publications pertain to nutrition topics that cover a diversity of health and nutrition interests for the general public.  She is also certified as a health and wellness coach.