Drink up

Hydration key defense against heat illnesses

The Post and Courier

It's hot. It's been hot. It's going to be hotter.

Get used to it. While summer officially has just begun, you can count on it being summerlike in the Lowcountry from mid-May to mid-October. It's a time of year when everyone who likes to do things outdoors needs to pay more attention to getting fluids, aka "hydrating."

Proper hydration is a key component to protecting yourself and your loved ones from getting heat illnesses, such as heat exhaustion and often-fatal heatstroke, not to mention just being healthy.

"Hydration, or having enough water in the body, is important because water is the body's most critical, essential nutrient," says local wellness expert Dr. Ann Kulze, noting that 65 percent of the body is made up of water. "Illness and death will ensue from lack of water much more quickly versus the other essential nutrients."

Water's vital functions on the body include virtually every chemical and metabolic reaction, the component in blood principally responsible for the delivery of oxygen and nutrients to cells, the removal of cellular waste products, the regulation of body temperature, the lubrication of the joints and mucous membranes of the nose, throat, mouth and gastrointestinal tract, and the cushioning of internal organs.

General guidelines

So what is proper hydration?

Unfortunately, there is no single answer. We humans all have varying hydration needs based on age, weight, diet, fitness and activity levels, heat tolerance and even our "sweat rate." Frankly, some of us sweat more than others.

Considering all those factors, the Institute of Medicine of the National Academies recently set general recommendations for water intake based on detailed national data. It showed men and women who appear to be adequately hydrated consume, respectively, about 125 ounces (3.7 liters) and 91 ounces (2.7 liters) of total water per day. About 80 percent came from fluids and 20 percent from food.

Another general guideline is 1 milliliter per calorie burned, which should be adjusted upward for physical activity, exposure to hot, humid conditions, altitudes of 8,000 feet or greater, illnesses that include symptoms of fever, diarrhea and vomiting, and pregnancy or nursing. That formula is not as complicated as it may seem. Burn 2,000 calories, you'll need 2,000 milliliters, or 2 liters of water. (Think 2-liter soft drink bottle, without the soft drink.)

Still, those are not one-size-fits-all recommendations. However, using that and your individual sensation of thirst may get you most of the way there.

"Thirst is a very reliable guide to the bodily needs for water in normal circumstances," says Kulze, though she notes the elderly are less sensitive to thirst and may need to be more proactive. "One urban legend is that, 'You are already significantly dehydrated by the time you are thirsty.' In reality, thirst kicks in way before you are clinically dehydrated."

Misconceptions

Partly because of the general nature of hydration needs, several myths and misconceptions have been perpetuated. Yet some, in fact, may have helped focus the public's attention on the need to drink water.

Perhaps the biggest myth has been the idea of drinking eight 8-ounce glasses of water per day. It turned out to have no scientific basis.

"It was a great way to get people to understand the importance of getting enough water," says Dr. Timothy Scheet, an assistant professor of health at the College of Charleston, noting that studies show dehydration rates among people have dropped.

He also credited the bottled water industry, whom some say helped perpetuate the misconception that bottled water was healthier than tap, for helping people drink more water.

"When I was growing up, we just had water fountains. I look around now and many people are carrying around bottles of water," says Scheet, adding the plethora of flavored waters, such Vitamin Water, have provided alternatives for those who don't like the taste of plain water.

Another indicator of proper hydration, the color of your urine, has various versions, such as you are dehydrated if your urine is not clear. (It's not true.) The correct one is that if urine is a dark yellow color, it's a good indication of dehydration. Ideally, urine should have a slight yellow tint (similar to the color of light lemonade) to it.

Effect of coffee, alcohol

Science has lightened up, to a degree, on the dehydrating effects of caffeinated beverages, such as coffee and tea, and alcohol.

Kulze says coffee and tea in standard "doses" of one to three cups does not have a diuretic effect (loss of fluid), though large quantities (seven or more) do. In fact, she adds, drinking one cup of coffee provides the same amount of hydration as a cup of water.

Likewise, she says that consuming one to two drinks of alcohol can contribute to hydration, though more than that can lead to fluid loss. In larger quantities, alcohol inhibits a hormone that helps retain fluids in the body.

Scheet says a good rule of thumb is to alternate one alcohol drink with one serving of water.

'Sweat rate'

Hydration is of even greater concern for those who exercise in hot conditions, whether it's high school, collegiate or pro athletes or weekend warriors.

"When athletes exercise in high temperatures, they rely mostly on evaporation for dissipating body heat. Evaporation can account for as much as 80 to 90 percent of heat loss for body cooling," says Dr. Susan L. Rozzi, director of the athletic training education program at the College of Charleston.

"Therefore, if sufficient fluids are not taken in prior to and during exercise to offset the amount of body fluid lost during sweating, dehydration can occur. When athletes lose weight during exercise, they are losing body fluid. Dehydration of 1 to 2 percent of an athlete's normal body weight can negatively impact performance, and when they lose 3 percent or more of their body weight, they are at an increased risk of developing an exertional heat illness, such as heat cramps, heat exhaustion or heat stroke."

She adds that while athletes think more about hydration in the summer months because of the increase in air temperature and humidity, fluid replacement is important whenever it is being lost during exercise.

Yet people sweat at different rates, even a soccer team that is similarly trained in similar conditions.

So calculating "sweat rates" is a precise way to predict hydration needs.

"Sweat rate is pre-exercise body weight, minus post-exercise body weight, plus fluid intake and minus urine excreted per hour," says Rozzi.

"So if an athlete weighs himself before a one-hour workout, then at the end and adds in the amount of fluid taken in during the hour and subtracts the urine excreted he can calculate exactly how much fluid he loses through sweating each hour. This would be an indicator of how much fluid he needs to replace."

The National Athletic Trainers Association strongly urges that pre-exercise hydration starts with consuming 17 to 20 ounces of water or sports drink two to three hours before exercise and another 7 to 10 ounces about 20 minutes before exercise. During exercise, athletes should consume fluid according to their sweat rates, which generally requires 7 to 10 ounces every 10 to 20 minutes.

Too much water?

The convergence of the weekend warrior and the hydration craze has raised awareness of a condition known as hyponatremia.

People who drink too much water and do sustained endurance activities, such as running, for more than four hours can dilute their blood sodium and suffer from hyponatremia, a condition that can start with nausea, headache, confusion and progress to convulsions or coma.

While the condition is rare, it underscores the importance of drinking beverages with electrolytes, aka sports drinks, containing sodium and potassium, for anyone exercising for more than one hour and extreme heat and sweating.

"If you're out of electrolyte balance," says Scheet, "you'll start to have cramps."

How much water?

General recommendations for daily water intake for men is 125 ounces (3.7 liters) and for women is 91 ounces (2.7 liters).

Another general guideline is 1 milliliter per calorie burned, which should be adjusted upward for physical activity, exposure to hot, humid conditions, altitudes of 8,000 feet or greater, illnesses that include symptoms of fever, diarrhea and vomiting, and pregnancy or nursing. Burn 2,000 calories per day, you'll need 2,000 milliliters, or 2 liters of water. (Think a 2-liter soft-drink bottle, without the soft drink.)

Pre-exercise hydration (especially for exercise lasting more than an hour and in hot conditions) starts with consuming 17 to 20 ounces of water or sports drink two to three hours before exercise and another 7 to 10 ounces about 20 minutes before exercise. During exercise, athletes should consume fluids according to their sweat rates, which generally requires 7 to 10 ounces every 10 to 20 minutes. Sweat rate formula: Sweat rate equals pre-exercise body weight minus post-exercise body weight plus fluid intake minus urine volume/exercise time in hours.

Reach David Quick at 937-5516 or dquick@postandcourier.com.