phillyphilly
01-20-2008, 11:40 AM
Drink To Your Health
Sure, you should drink regularly. But exactly how much water do you need? And why are some runners dying from excessive fluid consumption?
By Amby Burfoot
Your Daily Drinking Requirement
The old formula--everyone needs eight glasses of water a day--is out. It has been replaced by formulas based primarily on your gender and body weight. Here are the formulas for moderately active men and women:
Male Drinking Requirement, in fluid ounces:
Body Weight x .35
Female Drinking Requirement, in fluid ounces:
Body Weight x .31
Example: A 132-pound women needs to drink 41 ounces of water a day (132 x .31= 41). She'll get the rest of her daily water supply from food and metabolic processes. Runners need to drink extra to cover daily sweat losses. As she passed her coach and friends at the 15-mile mark of the 2002 Boston Marathon, Cynthia Lucero smiled and waved cheerily. It was typical behavior for the petite Ecuadorian native. According to all who knew her, Lucero loved life, loved to help others, and loved running. Seven miles later, however, something went horribly wrong.
It should have been the best of times for Lucero. The previous week she had defended her doctoral dissertation to become, in effect, Dr. Cynthia Lucero. The dissertation studied the positive effect of marathon training on cancer victims and their families. A member of Team in Training herself, Lucero had run her first marathon 2 years earlier, finishing in 5:19 at the Rock 'N' Roll event in San Diego.
Now Lucero was running her first Boston Marathon. She had trained well, and eagerly anticipated the day. Things seemed to go smoothly until the 22-mile mark, where she stopped to drink a cup of fluid. Another runner remembers hearing Lucero say that she felt dizzy and disoriented.
A few steps later, Lucero staggered briefly, then fell to the pavement, unconscious. She never regained consciousness, becoming just the second runner ever to die in the Boston Marathon, and the first to die of hyponatremia, which is caused by excessive fluid consumption.
We live in a water-obsessed culture. Every soccer kid has a water bottle or two. Mothers haul around gallon jugs in their minivans. And every business exec clutches a 20-ouncer while dashing through airports with a laptop and overnighter. Why? At least in part because every fitness article in every newspaper and magazine insists that you absolutely, positively must drink eight big glasses of water a day.
But where's the proof? Amazingly, there isn't any. Even in marathons, the available evidence indicates that overhydrating is a bigger health threat than underhydrating, with Cynthia Lucero's story serving as an unfortunate exclamation point.
Yes, we runners need to drink generously. No one questions that. But we need to drink with a fuller understanding of the facts, the medical science, and the potential risks.
I've been interested in this subject since early 1968 when I was a subject in one of the first experiments on hydration and performance. First, I ran a hard 2 hours on a laboratory treadmill while chugging fluids every 10 minutes. Then exercise physiologist David Costill sat me down on a chair and attempted to thread a long plastic tube through a nostril, down my throat, and into my stomach. I gagged and protested, but Costill persisted. He said he needed to drain my stomach to see how much of the fluids had actually been absorbed into my bloodstream. "Relax your throat," he said. "Just pretend you're swallowing some spaghetti."
Two months later Costill weighed me before (138 pounds) and after (129 pounds) that April's warm Boston Marathon. I had lost an alarming 6.5 percent of my body weight. And I felt like crap. Except for the winner's laurel wreath on my head.
Last winter, I spent several months talking to experts and reading everything I could find on the subject of human hydration needs. Here's the most interesting and useful stuff that I learned.
Hydration and Your Health
Water plays a crucial role in overall body health, but tales of near-universal dehydration seem to be exaggerated.
Water, water everywhere: Water is by far the largest constituent of the human body, making up about 60 percent of your total body weight. This large pool of water performs many crucial functions. Among them: It nourishes the cells; carries food throughout the body; eliminates waste; regulates body temperature; cushions and lubricates the joints; and maintains blood volume and blood pressure. Inadequate levels of fluid consumption have been associated with kidney stones, and higher rates of: urinary tract infections; bladder and colorectal cancers; and even heart disease in one or two studies.
Universal agreement: Given the above, all experts agree that an adequate water supply is crucial to the body's optimal functioning. The only question: How much water and other fluids do you need to drink per day?
The 8 x 8 myth: Most American adults believe that they should drink eight 8-ounce glasses of water a day. Why do they believe this? Because they have heard it countless times from all U.S. media, including this magazine. But there's little to no evidence supporting 8 x 8.
The good professor: Last summer a Dartmouth College professor named Heinz Valtin published a lucid and compelling article in the Journal of the American Physiological Society. Basically, Valtin committed himself to searching out medical-scientific verification for the 8 x 8 rule. He couldn't locate any.
"I have found no scientific proof that we must drink at least eight glasses of water a day," concluded Valtin, the professor emeritus of physiology at the Dartmouth Medical School. "The published data strongly suggest that we probably are drinking enough, and possibly even more than enough."
Of course, Valtin was researching the hydration habits of average, nonexercising Americans. Runners sweat heavily, and need to drink more than nonexercisers. And the heavier and more muscular you are, the hotter the temperature, and the faster you run, the more you will sweat.
Awash in water: Meanwhile, a survey of 2,818 adult Americans in 2000 by the International Bottled Water Association (IBWA) revealed that we are drinking 17.6 8-ounce cups of liquid a day. The IBWA argues that 6 cups of this amount is alcohol and caffeine drinks (both considered diuretics, meaning they increase urine production), and should therefore be subtracted from the total.
The truth about caffeine: However, research conducted in the last 2 years has reversed the age-old wisdom that caffeinated beverages are diuretics. Actually, to be more precise, the research confirmed that caffeinated beverages are diuretics--to the same degree as plain water. You drink a lot of water, you need to go potty. Same with caffeinated beverages, no more, no less.
"The research indicates that caffeine stimulates a mild diuresis similar to water," says heat and hydration expert Larry Armstrong, Ph.D., author of the just published Exertional Heat Illnesses. Armstrong reached this conclusion after analyzing 10 medical articles on caffeinated beverages, and published his report last year in the International Journal of Sport Nutrition and Exercise Metabolism.
Beating a path to the bathroom: Other experts agree with Valtin and Armstrong: There's no dehydration epidemic sweeping the country. If anything, we're overhydrated. This isn't necessarily a bad thing. It's probably just adding to your daily mileage and calorie burn, courtesy of all those trips to the bathroom.
But there's no evidence for the list of dehydration ills--fatigue, headache, dry skin, lack of concentration, and so on--put forth by some. "Without any convincing data, I remain skeptical of all these so-called dehydration problems," says Penn State University nutrition researcher Barbara Rolls, Ph.D., author of Thirst, and one of the country's leading experts on hydration. "It's a myth that's being perpetuated. The thirst mechanism is exquisitely tuned to keep us in fluid balance."
This just in: While most Americans seem to be consuming plenty of fluids, some still haven't gotten the message, including some regular exercisers. In late April, a study presented at the annual meeting of the IDEA Health & Fitness Association showed that nearly half of all exercisers at several Bally Total Fitness locations were dehydrated before their workouts.
Mars and Venus: When it comes to sweat rates and fluid-replacement needs, men and women come from different planets. Because men are on average significantly heavier than women and have more muscle mass, they sweat more than women, and need to drink more. Or, to turn things around: Women don't sweat as much as men, and don't need to drink as much.
An overlooked truth with real-life consequences: For the reasons just stated, a woman's hydration need can be up to 30-percent less than a man's. This essential fact has been largely overlooked in most articles on hydration needs, and it's particularly important for women runners, because most of the marathoners who suffer from hyponatremia (excessive fluid consumption), including a number who have died from marathon-related hyponatremia, have been women. More on that later.
Hydration Hall of Fame
The medical literature on sweat rates and fluid consumption tells the
story of many amazing athletes. A few highlights:
Ride Across America: A cyclist in the Ride Across America once consumed 28 liters (nearly 60 pounds) of fluid in 1 day. It just about killed him.
Alberto Salazar: During the 1984 Los Angeles Olympic Marathon, Alberto Salazar lost 11.9 pounds (8.1 percent of his body weight) while running 2:14:19 for 15th place.
Tour de France: Riders in the Tour typically consume about 44 ounces of fluid per hour of racing. Research shows that, for several key reasons, cyclists can consume more fluid than runners while going hard.
Ultramarathoners: In a 100-mile race in temperatures that reached 100 degrees, 13 finishers consumed 19.4 liters of water in 26 hours, for an average rate of about 24 ounces per hour.
An ultra ultramarathoner:
In 195 days of running more than 8,000 miles around Australia (44.5 miles a day), Gary Parsons maintained his weight and fluid balance by drinking about 6.4 quarts a day.
Hydration, Performance, and Risk
Dehydration diminishes performance, because it thickens the blood, decreases the heart's efficiency, increases heart rate, and raises body temperature. But a modest dehydration is a normal and temporary condition for many marathoners, and doesn't lead to any serious medical conditions. Excessive fluid consumption, on the other hand, can prove deadly.
The long and sweaty road: The first dehydration studies with marathoners were done at the Boston Marathon in the 1960s, during an era when runners were advised to avoid water-drinking because it caused stomach cramps. At any rate, race organizers provided no fluids en route. Result: The runners lost 5 to 6 percent of their body weight through sweating, but apparently suffered no particular harm.
A full tank: Since then, a substantial body of research has shown that anything more than a 2-percent dehydration will worsen performance, and everyone agrees that it makes sense to limit dehydration as you run. Some runners can even train themselves to drink more. Studies have also shown that the more fluid in your stomach, the more that reaches your blood, where you want it. Hence, the good advice to run with a comfortably full stomach and to "top off your tank" frequently.
Out of the lab, onto the road: Nonetheless, in the real world, the winners of any given marathon are probably the most dehydrated runners on the course. At sub-5-minute pace, they produce tremendous amounts of heat and sweat, and have little time for drinking. Even most runners who finish in 2- to 4-hours will sweat about twice as much as they drink. This can easily lead to a greater-than-2-percent dehydration. It's the drinking that limits us; the body doesn't like to run hard and drink hard at the same time. (At about 4-hour pace, it seems, runners are going slow enough, perhaps with walking breaks, that they can drink sufficiently to avoid most dehydration. Those athletes completing 5- and 6-hour marathons, and Ironman-type triathlons that last twice as long, can actually overhydrate.)
The sweat-rate paradox: As we get fitter, we sweat more. This means that we dehydrate faster--a cruel blow, it would seem. Of course, the body is smart. It knows that it can cope with modest dehydration. Heatstroke is the serious danger. So the body increases your sweat rate as you get fitter, because sweat promotes cooling, which helps hold heatstroke at bay.
The heatstroke threat: If you read the sports pages, you've seen the headlines about athletes dying from heatstroke. Usually, they're football players returning to training camp in the high heat and humidity of August. These guys are big, muscular, out-of-shape, and unable to deal with the heat/humidity combo. Dehydration can contribute to heatstroke, which is one of the prime reasons why all athletes are admonished to drink regularly.
The dog days of August: But dehydration doesn't cause heatstroke--it's more the big-guys-out-of-shape-in-August syndrome, particularly the high humidity. Marathoners rarely suffer from heatstroke because we're smaller, thinner, better conditioned, and less motivated (we're not going to lose a multimillion dollar contract if we don't impress the coaches with our hustle). We run our Houston and Miami marathons in the early morning of the winter months, not in August. Indeed, heatstroke is a bigger threat to college or Olympic 10,000-meter runners forced to compete in hot, humid track meets than it is to most recreational marathoners.
Hyponatremia deaths: As marathoning has boomed, and particularly as it has attracted more women and recreational runners, an entirely new health risk has intruded on our sport. It's called hyponatremia. Hyponatremia means "low blood sodium," but it's caused by excessive fluid consumption, which lowers the concentration of sodium in the blood. In extreme cases, hyponatremia can lead to brain seizures and death.
Last year, both the Boston Marathon and the Marine Corps Marathon had their first-ever fatalities attributed to hyponatremia. Hyponatremia is also beginning to appear in other endurance athletes, including ultramarathoners, Ironman triathletes, long-distance hikers, Army recruits, and even Iditarod cyclist-runners competing in sub-zero temperatures in Alaska. While no one knows for sure how many runners typically become hyponatremic, the 2002 Boston Marathon produced a 13-percent incidence rate. And the condition can be very serious.
Hyponatremia risk groups: Women, women, and women. This is not a sexist slam; it's a warning. Men can also drink excessively, and suffer from hyponatremia, as has happened in the Army. Nonetheless, a high percentage of exercisers suffering from hyponatremia have been women, including the Boston and Marine Corps deaths last year.
Why women? As already noted, they're smaller and less muscular than men, so they don't sweat as much. They also have a smaller blood plasma "tank" than men, which is easier to overfill. Many women are new marathoners who are happy to finish in 5 hours or more. They have heard that marathoners must drink as much as possible, so that's what they do. They reach the 20-mile mark exhausted (who doesn't?), and think, "If I can force myself to drink more, I'll feel better." It's a recipe for disaster.
New Views on Fluid Consumption
The hyponatremia issue has forced sports and medical groups to take a new look at their hydration guidelines, and several have already adjusted their recommendations.
Boot camp: The Army has put new recruits through a period of hard physical training since day one, but the first hyponatremia death wasn't reported in the journal Military Medicine until early 1999. Two years later, the same publication brought news of 17 hyponatremia cases in a 2-year span, along with the statement: "The authors conclude that hyponatremia resulted from too aggressive fluid replacement practices for soldiers in training status." The Army's fluid-replacement recommendations have since been lowered.
Marathon medicine: Last fall, the International Marathon Medical Directors Association (IMMDA) issued the first fluid-consumption guidelines from a medical organization completely focused on runners (as opposed to, say, soccer, baseball, or football players). IMMDA, which represents some 150 major marathons on all seven continents, suggests that marathoners should consume 13 to 27 ounces of fluid per hour, with an absolute ceiling at 27 ounces. For more, visit aims-association.org/immda.htm.
That's about half the fluid requirement proposed since 1996 by the widely quoted "Exercise and Fluid Replacement" position stand of the American College of Sports Medicine, which calls for 20 to 40 ounces per hour. For more, visit acsm-msse.org, and click on "Position Stands."
Boston Marathon and USA Track & Field: For the first time in its 107-year history, the Boston Marathon this spring provided all 20,000 runners with a fold-out pamphlet from the American Running Association and the American Medical Athletic Association. It advised runners to stay hydrated but not to overdrink, to maintain a salty diet, to favor sports drinks, and to recognize warning signs. Also at Boston, USATF released its first-ever guidelines, "Proper Hydration for Distance Runners," which recommended that runners weigh themselves before and after long, hard training runs to determine their own unique sweat rate. For more info, visit usatf.org/coaches/library.
A note from our friends at Gatorade: Sure, they're an advertiser. But the thing we like most about Gatorade is the company's long commitment to supporting research and education efforts on topics relating to fitness, nutrition, and health. The Gatorade Sports Science Institute (gssiweb.com) has recently published one of the most comprehensive advisories on hyponatremia, "Hyponatremia in Athletes." Here you'll find everything from the possible effects of a recessive Cystic Fibrosis gene to a section on metabolic water production while running. Mostly, the folks at Gatorade want you to know that proper hydration is important, and that you're an experiment of one. That is, each of us sweats at a different rate, produces varying amounts of sodium in our sweat, and reacts differently to heat stress.
Our Recommendations
We also believe that it's a good time to review your hydration practices. Runners need to pay more attention to their daily fluid consumption than most people, but we don't need to be obsessive. Given half a chance, the body will self-regulate to a normal, healthy state of fluid balance. Our recommendations:
1. Drink generously, but appropriately. Know yourself and your needs, and make adjustments for the weather. A runner training through the summer months in Chicago for a fall marathon may need to drink more during and after a slow 16-miler in August than during and after an all-out marathon effort on a cool October morning.
2. Use sports drinks. Before, during, and after workouts and races, drink specially-formulated sports drinks. These drinks contain the water you need, appropriate amounts of carbohydrates, and small amounts of sodium. It's the combo of all three that really helps you in the long run.
3. Pay particular attention to postexercise rehydration. You're likely to become temporarily dehydrated during a long, hard run, so make sure you drink enough afterward. The same goes for food. Get your fluids, get your carbohydrates, get a little sodium, get a little protein--and you'll be fine.
4. Weigh yourself daily during periods of intense training. If you're losing weight, make sure it's from fat loss, not chronic dehydration. You can also check your urine color. It should be clear or light yellow (unless you have recently taken some B vitamins, which can turn the urine bright yellow).
5. When running long and slow--4 or 5 hours or more--monitor your fluid consumption. Be sure you're not drinking more than you need. Also, consider running with a salty snack that you consume at the 20-mile mark. If you're a woman, pay particular attention to these recommendations.
6. Drink when you're thirsty. While it's true that your thirst doesn't kick in until you're 1- to 2-percent dehydrated, there's nothing terribly wrong with that. Remember: Your body has an "exquisitely tuned" water-balance mechanism. Use it.
Water in, Water Out
Your daily water supply comes from three sources, and you lose water in four principal ways. The percentages shown here are averages for nonexercisers. Runners sweat more, and need to drink more, than nonexercisers.
Water Intake Percent Water Loss Percent
Fluids 60% Urine 50%
Food 30% Sweat 35%
Metabolism 10%* Respiration 10%
Feces 5%
Actual percentages will vary considerably, depending on the weather, your diet, the amount you exercise, and other factors. *Approximately 10 percent of your daily water supply comes from metabolic water, which is water that's "liberated" within the body when you burn fats and carbohydrates.
What We're Drinking
According to a survey of nearly 3,000 American adults in 2000, our typical daily beverage consumption looks something like the following:
Beverage Amount
(8 oz. cups)
Water 6.1
Coffee 2.0
Juice 1.9
Milk 1.7
Soda, with caffeine 1.7
Tea 1.2
Alcohol (1.0)
Soda without caffeine .9
"New Age" drinks .6
Sports drinks .5
TOTAL: 16.6 cups*
(132.8 ounces)
*Total does not include the alcohol, which is a diuretic. Note: Your daily water supply includes an additional 3-plus cups that you derive from foods and metabolic water.
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