It is hard to say enough good things about water. Water is the most abundant compound in the human body, making up about 60 percent of the body weight in adults. It fills virtually every space in cells and between them. All biochemical reactions occur in water, and water is an active participant in those reactions. From energy production to joint lubrication to reproduction, there is no system in your body that does not depend on water.
But with all the obvious importance of water, it appears that most of us aren’t drinking enough. Nearly one-third of the U.S. population is walking around slightly dehydrated. “So what?” you ask. “What’s the big deal about being slightly dehydrated?”
A voluminous problem
Just about everyone knows that you can get pretty sick and even die from severe dehydration. But the fact is that chronic, mild dehydration – a constant 1 to 2 percent deficit of body weight caused by loss of fluids – can have a measurable effect on mental and physical performance, muscle growth, and even long-term health.Water and your muscles
Since muscles are nearly 70 percent water, even a small loss of fluid will affect their function. Muscles are controlled by nerves. The electrical stimulation of nerves and contraction of muscles occurs due to the exchange of electrolytes dissolved in water across the nerve and muscle cell membranes.- If you’re low on water or electrolytes, your muscle strength and control are weakened.
- A water deficit of just 2 to 4 percent of your body weight can cut your strength-training workout by as much as 21 percent, and your aerobic power by a whopping 48 percent!
If gaining muscle is your goal, then you should care about cell volumization, or the hydration state of your muscle cells. In a well-hydrated muscle cell, protein synthesis is stimulated and protein breakdown is decreased. On the other hand, muscle-cell dehydration promotes protein breakdown and inhibits protein synthesis.
Cell volume has also been shown to influence genetic expression, enzyme and hormone activity, and metabolic regulation.
Water and your body fat
As you mobilize your stored fatty acids to burn off as energy, you release any fat-soluble toxins that have been benignly stored in your fat cells. The more fluid you drink, the more dilute the toxins in your bloodstream, and the more rapidly they exit from your body.When your goal is losing body fat, water is your friend.
- Drinking an adequate amount of water can help take the edge off hunger so that you eat less. And water has no calories.
- If you are on a high protein diet, water is required to detoxify ammonia, a by-product of protein energy metabolism.
Water and your brain
When it comes to peak mental capacity, whether at the office or in competition, your hydration state will affect your performance. In a study of subjects’ abilities to perform mental exercises after heat-stress induced dehydration, a fluid loss of only 2 percent of body weight caused 20 percent reductions (as compared to their well-hydrated state) in:
- Arithmetic ability
- Short-term memory
- The ability to visually track an object
Kidney stones, cancer, heart problems
Probably most surprising is the effect that chronic, mild dehydration has on health and disease. It was a practice of Hippocrates to recommend large intakes of water to increase urine production and decrease the recurrence of urinary tract stones. Today approximately 12 to 15 percent of the general population will form a kidney stone at some time.Many factors can modify the urinary risk factors for developing stones.
- Of these, diet – especially fluid intake – is the only one that can be easily changed and that has a marked effect on all urinary risk factors.
Several studies have discovered a direct correlation between fluid intake and the incidence of certain cancers.
- Studies in Israel, Great Britain, and the United States have observed that the more fluid that people drink, the lower their risks of bladder, prostate, kidney, testicle, renal pelvis, ureter, colon, and breast cancers.
In some of the studies, a decrease in cancer risk was specifically associated with water intake.
- A study in Seattle Washington showed that women who drank more than 5 glasses of water a day had a 45 percent decreased risk of colon cancer, versus those who consumed 2 or fewer glasses per day. Men had a non-statistically significant reduction of cancer by 32 percent when they drank more than 4 glasses a day, versus 1 or fewer glasses a day.
- Although the data are preliminary, a pilot study in Great Britain found that the risk for developing breast cancer was reduced by 79 percent among water drinkers when adjusted for all other related factors.
Mild dehydration can also be a factor in the occurrence of mitral valve prolapse.
- In a study of 14 healthy women with normal heart function, mitral valve prolapse was induced by mild dehydration, and resolved with rehydration.
Your fluid plan
Contrary to our drive to eat, our drive to drink is not as keen. Our thirst mechanism doesn’t kick in until we are already mildly dehydrated.When you’re working out moderately in a mild climate, you are probably losing 1 to 2 quarts (2 to 4 pounds) of fluid per hour through perspiration. That means that a 150-pound person can easily lose 2 percent of their body weight in fluid (3 pounds) within an hour. If exercise is more intense or the environment is more extreme fluid, losses will be greater. You can see how easily you become dehydrated.
- If you don’t replenish your fluid losses during exercise, you will fatigue early and your performance will be diminished.
- Without fluid replenishment after exercise, your performance on successive days will decay, and your long-term health may be at risk.
Design a fluid plan just like you plan your food. To cover your minimum intake, make sure you drink non-caffeinated and non-alcoholic beverages all day, as follows. Since alcohol and caffeine can promote water loss, make at least 5 of your beverages water.
- A couple cups when you get up in the morning
- A few more cups mid-morning
- A couple cups at lunch
- Two more in the mid-afternoon
- Two more at dinner
Then add what you need to be well hydrated before, during, and after exercise.
Monitor your hydration status. One of the easiest ways is to check your urine; it should be relatively odorless and no darker colored than straw. Anything darker is a good sign that you are dehydrated and need to be drinking more.
Don’t get caught empty-handed
Many factors increase water requirements, including high heat, low humidity, high altitude, exercise, dieting, illness, travel and pregnancy.- Carry water and fluids with you as a constant reminder to drink.
- Freeze fluids in water bottles to keep them cold during long-distance exercise.
- Remember that fruits and vegetables are great sources of water.
Symptoms of dehydration
| Early signs | Severe signs |
| Fatigue Loss of appetite Flushed skin Burning in stomach Light-headedness Headache Dry mouth Dry cough Heat intolerance Dark urine with strong odor | Difficulty swallowing Stumbling Clumsiness Shriveled skin Sunken eyes and dim vision Painful urination Numb skin Muscle spasm Delirium |
Fluid intake guidelines
- Drink a minimum of 1 quart (4 cups) of fluid for every 1,000 calories you eat every day.
- Drink at least 5 cups of water every day.
- Fluids should be cool.
- For moderate exercise that lasts an hour or less, water is sufficient for replacing lost fluids. If you like flavored drinks better, then use flavored beverages.
- For intense exercise that lasts less than 1 hour and exercise lasting more than an hour, carbohydrate-electrolyte sport drinks are best.
- Drink 2 cups of fluid 2 hours before exercise.
- Drink 4-6 ounces every 15 to 20 minutes during exercise.
- After exercise, drink 16-20 ounces (2-2½ cups) of fluid for every pound of body weight lost during exercise.