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Sports Drinks May Cut Clot Risk from Travel

Study suggests they keep blood thinner than when drinking water

TUESDAY, Feb. 19, 2002 (HealthDayNews) -- If you want to reduce the risk of blood clots when you take long flights, you might try being like Mike.

Japanese researchers say sports drinks -- such as Powerade or the Gatorade that Michael Jordan pitches -- may help thin your blood during air travel and possibly lower the propensity for clotting in your legs.

Marathon flights have been linked to an increased risk of deep vein thromboses (DVT), which forms in the legs and can migrate into the lungs. Once there, they can starve parts of your organs of oxygen, causing potentially deadly damage.

A report on the findings appears as a research letter in tomorrow's issue of the Journal of the American Medical Association. Otsuka Pharmaceutical, the maker of Pocari Sweat, a sports drink that competes with Gatorade and is sold in Asia, funded the research.

Dehydration may play a role in the formation of leg clots, and some doctors recommend that people who take long-haul flights -- or spend a lot of time planted in any seat, for that matter -- drink as much water as possible while traveling.

However, the new study suggests an electrolyte drink may keep passengers better hydrated and, although it's still pure speculation, make them less susceptible to blood clots. Experts say the relatively salty water in those beverages stays in the body longer than water alone, preserving a higher blood volume. Yet, there's no direct evidence yet linking blood volume to deep-vein clotting.

"Increasing the amount of fluid in the blood would reduce the dehydrating effect of being in a dry environment" such as an airplane cabin, says Dr. Clive Kearon, a DVT expert at McMaster University in Hamilton, Ontario. However, it's not clear that losing water promotes leg clots. Other factors, such as sitting in a cramped position and, for air travel in particular, getting less oxygen in the lungs may matter more, Kearon says.

In the latest study, a research team at Otsuka led by Koichiro Hamada compared an electrolyte drink -- containing sodium, potassium and carbohydrates -- with plain water in 40 healthy men taking a nine-hour flight in coach class.

Half of the men, whose average age was about 23, were given 340 milliliters of liquid (a little less than 12 ounces) just before takeoff and 150 milliliters two hours later with a meal. They drank another 340 milliliters 3.5 hours into the flight, 150 milliliters with a snack 5.5 hours after takeoff, and 340 milliliters at 7.5 hours, for a total of 1.32 liters. The researchers collected urine samples from the men every two hours, and recorded their body weight before takeoff and at landing.

Men who drank the electrolyte drink retained far more fluid and had a greater blood volume than those given just water, the researchers say. Much of the difference was the result of less urine output from those who drank the beverage compared to the water drinkers.

Blood viscosity in the arms and feet wasn't significantly different in the men given the electrolyte drink. However, for those given water, blood drawn from their feet was markedly more viscous than that taken from their arms. Higher viscosity at the feet "may contribute to the formation of blood clots in the lower limbs," the researchers write.

The cause of deep-vein clots is elusive. However, the ratio of oxygen-carrying red cells in a volume of blood -- a proportion known as the hematocrit -- plays a role, and people with very high hematocrit are known to clot more easily, says Dr. Chi Van Dang, a blood disorders specialist at John Hopkins University in Baltimore.

It therefore makes sense, Dang says, that keeping blood relatively dilute "could be protective" against clots.

While higher blood volume may reduce the risk of clots, it may not, and it's not always benign. Since the body's vessels are a closed system, increased blood volume boosts blood pressure. Although that's not likely to be much of a problem during a long flight, Kearon says it could be dangerous for people with heart conditions.

What To Do

For more on DVT, try the University of Michigan, and for more on pulmonary embolism, try Medline.

To learn more about clotting and other blood disorders, check out Johns Hopkins.

For more about the health concerns associated with flying, try the National Academy of Sciences.

SOURCES: Interviews with Clive Kearon, M.D., Ph.D., associate professor, McMaster University, Hamilton, Ontario; Chi Van Dang, M.D., Ph.D., professor of medicine, oncology, pathology, molecular biology and genetics, and director, division of hematology, Johns Hopkins University School of Medicine, Baltimore; Feb. 20, 2002 Journal of the American Medical Association
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