To Drink Or Not To Drink? - New Study Questions Hydration Mantra

During training and endurance events, athletes should be careful not to ingest more fluids than necessary.

In April, an article published in the New England Journal of Medicine sent shock waves into the realm of endurance sports. Athletes – marathoners and triathletes – can over hydrate, even to the point of death. What? You can DRINK too much? Doesn’t every coach, nutritionist--even fellow athlete--tell you that you should hydrate while running, biking or swimming? So what’s a new triathlete to believe? Drink or don’t drink? Well, Dr. Balu Natrajan, a member of the American Medical Society of Sports Medicine Society attempts to sort out what the study’s finding means and what it doesn’t for BTers.

By Balu Natarajan, M.D.
American Medical Society for Sports Medicine

 

The study details
An increasing number of marathon runners are at risk for developing dangerously low sodium levels. In an article this month in the New England Journal of Medicine, Dr. Christopher Almond et al. reported on runners who were studied in the 2002 Boston Marathon. Of 488 runners who had their blood analyzed at the end of the race, 13% had hyponatremia, reflecting low sodium blood levels.

Various characteristics of the runners were studied, including age, race, gender, body-mass index, marathon experience, weight, use of anti-inflammatory pain medications, and intake of fluids during the endurance event. Analysis revealed that those individuals who did develop hyponatremia were the ones that tended to gain weight, take longer to finish (4 hrs or more), and be at either extreme of body-mass index.

On the basis of this and previously reported data, the authors concluded that excessive consumption of fluids is the single most important factor associated with hyponatremia. During training and endurance events, athletes should be careful not to ingest more fluids than necessary. In an accompanying editorial in the same issue of the Journal, Dr. Benjamin Levine and Dr. Paul Thompson noted that the international sports medicine community is developing updated guidelines for fluid intake during exercise.

AMSSM Physician’s comments:

The description of hyponatremia during marathons is nothing new. In the U.S., it was observed as early as in 1986 during the Pittsburgh Marathon. During the last 10 years, sports medicine professionals have seen increasing numbers of affected individuals in various marathon medical tents. In large part, this has to do with the rise in the number of charity runners in recent years. Many of these individuals tend to be slower runners, yet they continue to drink fluids often – sometimes at every mile marker. Consequently, they gain weight, overwhelming the body’s ability to get rid of the extra fluid. They also tend not to sweat as much as other runners, so they dilute their blood sodium levels to what can amount to dangerously low levels. Because of this medical problem, some marathon medical teams test sodium levels before starting IV fluids in at-risk runners who are seen for medical attention after events.

 

How do you find out if you are at risk?

The purest scientific approach would involve your sports medicine physician testing your blood sodium levels before and after a 20-mile training run. This approach, however, is generally not practical.

In general, you can let thirst and your energy levels be your guide to fluid intake

Alternatively, you could weigh yourself before and after your long runs. If you are gaining weight during the run, you are drinking too much! Some athletes ask if they should drink water or electrolyte drinks during the race. The sports medicine literature suggests using electrolyte drinks for events lasting more than one hour. However, electrolyte drinks don’t contain enough sodium to maintain your blood sodium levels if you drink too much. So moderate your fluid intake. Don’t bother trying to make your urine clear before a race, and make sure you don’t gain (water) weight during aerobic exercise.

The guidelines for fluid and nutrition can seem confusing, especially as recent research seems to suggest a departure from previous recommendations. If you do have questions about what approach to take, see your sports medicine physician.

 

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This information, prepared by members of the American Medical Society for Sports Medicine, is not medical advice and should be used for informational purposes only. Please consult your own physician or health care provider about any opinions or recommendations with respect to your symptoms or medical condition.