No matter your dietary plan, drinking lots of water is one piece of advice that is always consistent. Water’s importance in the human body is not inconsequential. In fact, while a person can likely survive a month without food, it could survive only about 3 days without water. It truly is one of the most important factors in our survival. But why exactly?
For starters, water makes up approximately 60% of our body weight. Our cells are composed of mostly water. When we think about this we begin to understand why lack of water–also known as dehydration– can be so damaging. Dehydration is defined as a condition that occurs when the body loses too much water and other fluids that it needs to work normally. Dark-colored urine–looking like apple juice–is an indication of dehydration. When dehydration sets in, symptoms like thirst, dry mouth, and less urine begin to appear. Continued denial of water leads to problems with blood pressure, heart rate and body temperature, and eventually, death. So just how does our body use water to keep us healthy and operating at peak performance?
Water is vital in facilitating every action that takes place within our bodies. The main functions of water can be loosely categorized into four basic topics: Transportation, chemical reactions, lubricant/shock absorber, and temperature regulation.
First, transportation. More substances dissolve in water than in any other liquid and it’s this quality that allows for substances in the body to be transported. Blood, the primary transport fluid in the body, is mostly made up of water. Dissolved substances in blood include proteins, lipoproteins, glucose, electrolytes, and metabolic waste products, such as carbon dioxide and urea, all of which are either dissolved in the blood and transported to cells to support basic body functions, or removed from cells and transported to be eliminated from the body.
Next, water is the main medium for chemical reactions in the body as it can store a large amount of heat, and is neither acidic nor basic. While water, with zero calories, cannot itself provide energy, it works to generate metabolism, enabling the body to derive energy from ingested nutrients. Another important chemical reaction requiring water is breathing. Respiration is a chemical change as new substances like carbon dioxide and water are formed. The lungs consist of 85% water. In order to take in oxygen and eliminate carbon dioxide, our lungs must be continually moistened with water. These are just 2 examples of chemical reactions that are vital to life. In each cell, around a billion biochemical reactions occur per second. That means around 37 billion trillion biochemical reactions are taking place in our bodies every second. And since all of these interactions require water. . . well, you get the drift.
Water has another important function as a lubricant and shock absorber and is the main component of the fluids that protect and lubricate tissues. Some of these systems being protected include:
- The brain and spinal cord
- A pregnant woman’s developing baby
- The lungs
- The gastrointestinal tract
- Joints and muscles
And finally, water regulates body temperature. The body uses water as a coolant, helping to regulate body temperature during exercise, fever and in hot environments. Water also has a high heat capacity, which means that it can absorb a significant amount of heat energy without a large increase in temperature. This property is crucial for regulating temperature in our bodies, as it allows us to maintain a stable body temperature even in both hot and cold environments. Human life has a narrow range of temperature, with the temperature set point of the body being 98.6°F. Too low or too high of a temperature causes enzymes to stop functioning and metabolism to stop. At a cool 82.4°F muscle failure occurs and hypothermia sets in. At the opposite hot end of the spectrum, 111.2°F the central nervous system fails and death results.
There are several mechanisms in place that move body water from place to place as a method to distribute heat in the body and equalize body temperature. The hypothalamus in the brain is the thermoregulatory center. The skin also contains temperature sensors that respond quickly to changes in immediate surroundings. When the surrounding temperature is cold, sensors in the skin send a signal to the hypothalamus, which then sends a signal to smooth muscle tissue surrounding blood vessels causing them to constrict and reduce blood flow. This reduces heat lost to the environment, keeping us warmer.
And if these reasons weren’t enough, here are some other ways in which your body uses water:
- Prevents constipation and kidney stones
- Keeps mouth, nose and throat moist, helping to create saliva
- Prevents bad breath
- Aids with digestion
- Keeps your brain working well
- Prevents fatigue
- Keeps kidneys healthy
- Prevents headaches
- Reduces anxiety
- Helps with weight loss
- Promotes healthy skin, hair, and nails
So we can all agree on water’s importance. But how much should we be drinking? Every day your body loses 8-12 cups of water through breathing, perspiring, urine and bowel movements, so this is a minimum you should be drinking to replace basic daily loss. Add more if you’re exercising, it’s hot, you’re eating a high fiber diet, or drinking alcohol.
The good news is, nearly all liquids count toward your hydration goals. While some may be better than others, based on sugars or other ingredients, they are all equally hydrating. Tap or bottled water, flavored waters, soda waters. Even sodas, coffees and teas, previously thought to be dehydrating, still count toward your water intake. The caffeinated effects of more frequent urination do not take away from their hydrating benefits. The one exception to this rule is alcohol, which is a big dehydrator. So if you’re having a drink with dinner, be sure to include an extra glass of water.
Further good news: The foods we eat also contribute to our hydration. In fact, about 20% of our water intake comes from food. Some are obvious: Soups, stews, popsicles, even yogurt. Not surprisingly, fruits and vegetables are good sources of water. Cucumber and watermelon are big winners at over 90% water. Try adding some fruit to your water to add more flavor (and water, and other nutrients!).
You probably now have a good idea of why you should drink water and some good sources. But maybe you’re looking for ideas to increase your daily water intake. Setting a goal often helps. Fill your water bottle first thing in the morning and make it a goal to fill, and drink 2 more full bottles for a total of 3. Or drink during times that could trigger a reminder: First thing in the morning (even before coffee), then again before you leave the house, before meals, after using the bathroom. Whatever cues work for you.
Is it possible for your body to have too much water? Yes, it’s called hyponatremia and it affects between 3 million and 6 million people in the US annually. It can cause water toxicity, which is when your body’s water level is more than your kidneys can excrete. This can lead to a dangerous electrolyte imbalance. Endurance athletes, such as those who run marathons and triathlons, sometimes drink too much water before and during an event. In healthy people, athletes are at the highest risk for overhydration.
Hyponatremia can also occur in nonathletes, often in older adults, who may be on certain medications or have conditions that can lead to water retention and hypnoatremia. In these cases it is not usually the result of drinking too much water.
But for the vast majority of us, the opposite is more often true: We need more water. Experts say, don’t wait for the cue of thirst. By that point you’re already nearing dehydration. Your urine is the best indicator. It should be closer to clear than a deep or dark yellow. Make a plan and goal to drink your 8-12 cups daily and add in extra when needed to replace extra losses from sweating, or alcohol use. And I just had another idea to help you hit your goal. Drink a glass every time you finish reading a blog!
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