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Home > Health & Wellness > The Importance of Hydration

The Importance of Hydration

Amanda Hewson – Medical Support OffShore Medical Trainer

At its basic level, hydration is simple. Feel thirsty? Drink something. Heading into an epic meeting? Bring along a water bottle. Despite this simplicity, there’s an ocean of misleading information out there that leaves people confused.

  • Eight glasses a day, or not?
  • Drink before you’re thirsty, or only when thirst hits?
  • Does coffee really dehydrate you?

Knowing the answers is vital, since hydration is key to your performance. “Water is necessary for every metabolic process in your body,” says Penny L. Wilson, Ph.D., R.D.N., a dietitian at Houston’s Memorial Hermann Ironman Sports Medicine Institute. “It transports nutrients to your cells and takes waste away from them. It’s like oil in a car.”

Water is probably the most overlooked essential nutrient. Lack of water intake leads to dehydration. Dehydration is usually described as state in which body loose fluids and salts below normal level. According to (Ericson, 2013) 75% of people are chronically dehydrated. Dehydration is related with many metabolic processes; for instance, dehydration of in excess of 5% of body weight can decrease the capacity for work and reaction times by about 30% (Sawka and Pandolf 1990). In his paper Mitchell et al. 1945, described chemical composition of the adult human body where it says that the brain and heart are composed of 73% water, lungs are about 83% water, skin contains 64% water, muscles and kidneys are 79%, and bones 31%. Mental symptoms of dehydration often include brain fog, lack of clarity and focus.

Question: Is thirst a good hydration tool?

Thirst is definitely a very strong predictor of hydration needs—and some experts would argue it’s the only one you need. “Our thirst mechanism is pretty accurate,” says Yeargin. “But it’s always a good idea to have some other methods to ensure you’re hydrated.” Knowing your sweat rate is one way to track your needs, particularly for endurance exercise and manual work, says Doug Casa, PhD. To calculate your sweat rate, weigh yourself naked before and after an hour of exercise or hard work. Keep track of how many litres or ounces you consume during the exercise and factor that into your calculation post exercise. Every Kg or pound you lose translates to about 0.5 litre or 16 ounces of fluid. “Your goal isn’t to match your sweat rate,” says Casa, “but you should try to get as close as is comfortably possible.

Critics of drinking extra water, beyond that from being thirsty often suggest that people will drink as much as they need, as the perception of thirst will guide their intake. However, physiologically, there are body indicators suggesting dehydrating effects have occurred before the feeling of thirst is perceived. For example, in a thorough review by Maughan et al. they concluded that: “Indicators such as a reduction in urine output and failure to maintain body mass are more reliable measures of dehydration than the feeling of thirst.” Oakley and Baird state the fact that healthy individuals can well tolerate a reduction of water volume of up to 5-10% of body weight at rest, the reliance on waiting to feel thirsty is definitely not an ideal way to guide water intake.

Susan Yeargin, Ph.D. says “The eight glasses a day is totally arbitrary”. “Everybody, especially athletes, have different needs.” The Institute of Medicine guidelines are more specific, recommending 2.6 litres or 91 ounces per day for women and 3.5 litres or 120 ounces for men. The institute believes that “the vast majority of healthy people adequately meet their hydration needs by letting thirst be their guide.

Question: Must we drink eight glasses of water a day?

Do Patients Drink Enough Water? Actual Pure Water Intake Compared to the Theoretical Daily Rules of Drinking Eight 250 ml or 8-Ounce Glasses and Drinking Half Your Body Weight in Ounces

Oakley & Baird from a recent study, believe the guideline of drinking half body weight in ounces (one ounce is equal to a small 250 to 300 m glass) would be more hydrating than the 8 glasses a day rule.

They assessed how much water hospital patients should be drinking based on the theoretical rule of drinking half your body weight in ounces, they determined that most patients were again deficient, but even more so then going by the 8 glasses a day rule.

On average, the sample was 6 glasses short of making their daily requirements based on the half body weight assumption. The results may be quite alarming considering many patients drank little to no water a day. For example, 36% of the sample drank 2 or less glasses of water a day. Even under sedentary conditions the body requires 0.3 litres per hour; even more, under extreme heat and/or exercise the body may lose and therefore require many litres of water in a single day.

Their conclusion was the majority of their sample did not drink enough water, whether going by the 8 × 8 or the 1/2BW rule of thumb. On average patients were 3 – 6 glasses short of ingesting an ideal water volume. Oakley & Baird found the guideline of drinking half body weight in litres or ounces would be more hydrating than the 8 glasses a day rule.

Question: Does clear urine mean you are hydrated?

Clear urine is a bit excessive. “As long as it is a pale yellow, like lemonade, you’re hydrated,” says Yeargin. If it’s completely clear, it just means you’re full to the brim; what’s going in’ is coming out. On the other hand, if your pee is the colour of apple juice or darker, or particularly smelly, you need to drink up.



Question: Does Caffeine dehydrate you?

While caffeine provides a performance-boosting edge, it also acts as a diuretic, correct? Not exactly. “Recent research shows that caffeine doses between 250 and 300 milligrams—about two cups of coffee—will minimally increase urine output for about three hours after consuming it,” says Yeargin, “But the research also shows that exercise seems to negate those effects. If you exercise, or work hard, within one to two hours of drinking coffee, you don’t pee more. “Most likely, during exercise, blood flow shifts toward your muscles and away from your kidneys, so urine output isn’t affected, Yeargin explains. In addition, if you always have a latte in the morning or a soda at lunch, your body is acclimated to the caffeine, so its effect, on both your physiology and performance, is minimal.

Question: Can you drink too much?

“You absolutely can drink too much,” says Casa, “and it can be deadly.” Too much water can cause symptomatic hyponatremia, a condition where the sodium levels in the blood become dangerously low. Although Casa estimates that fewer than one percent of marathoners develop symptomatic hyponatremia, certain groups are more prone to it, including smaller athletes; and those who do a significant amount of walking and running in cooler weather (when your sweat rate isn’t as intense as it is on warm days). “For most, the best way to prevent hyponatremia is to listen to your thirst,” says Casa

Question: Is drinking lots of water a good way to “detox?”

“There is no evidence that excess water makes your body more clean,” says Dr. Stanley Goldfarb, M.D., a professor of medicine in the Renal, Electrolyte, and Hypertension Division at the University of Pennsylvania’s Perelman School of Medicine. “If anything, drinking too much water can slightly impair the ability of the kidneys to filter blood.” He adds that the only people who should drink more water with a focus on their kidneys are those who have had kidney stones. It is, however, vital to drink clean water. If you are drinking good quality water you are not drinking the right water source for you.

Question: Does staying hydrated eliminate your risk of heat stroke.

Heat stroke is a life-threatening condition where your body temperature rises above 38 degrees. Dehydration can make you more prone to it. “People who are dehydrated are hotter,” says Casa. In fact, in a study published in the Journal of Athletic Training, Casa determined that for every one percent of body mass lost through sweat, your body temperature increases by half a degree, “which makes hydration hugely important for preventing heat stroke,” he says. But there are still a number of other factors that play a role. Body size, exercise intensity, fitness level, and age as well as humidity and air temperature can affect who does or doesn’t develop heat stroke, says Casa. Certainly staying hydrated is a good call and can reduce your risk, but paying attention to the whole picture is a better predictor.


What is the latest in hydration research?

In his work Yves Van Assche, 2015 wanted to establish a rate of rehydration of people who with serious dehydration problem.  The author used a 30 min bath session in hydrogen saturated water and breathing 2L/min hydrogen added to regular air and drinking 0,5L hydrogen enhanced water. It was noticed 3, 9% increase in hydration level in one single session. In their study Aoki et al. 2012 investigated effects of drinking molecular hydrogen rich water on muscle fatigue in athletes. Authors concluded that dehydration in athletes may also lead to fatigue, poor performance, decreased coordination, and muscle cramping. Authors also recommend drinking molecular hydrogen water as effective fluid hydration strategy for nutritional hydration.

Dehydration is known to cause an increase in production of reactive oxygen species (ROS) that leads to lipid peroxidation and nucleic acid damage causing severe consequences on over all metabolism (Breidert et al. 1994). By definition ROS is a type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell. A build-up of reactive oxygen species in cells may cause damage to DNA, RNA, and proteins, and may cause cell death. Reactive oxygen species are free radicals, also called oxygen radical. Molecular hydrogen has well known antioxidant properties; it selectively neutralizes only harmful hydroxyl radicals, bonding with 2 hydroxyl radicals it turns into water molecule (H2 + 2 OH – > 2 H2O).


Proper hydration means, aiming to drink clean filtered water at the very least as soon as you feel thirsty and for best results drinking half your body weight in ounces. As the research indicates, you need a half ounce of fluid per day for every pound of body weight. For example, if you weigh 160 lbs (72kg) you need 80 oz  (2.3 litres). This may sound a lot but it is only 10 small glasses a day, which is less than one an hour during waking hours. So we challenge you to drink for your weight this month and see if being hydrated really can enhance your life. It could be the “magic pill” you were looking for!


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