Endurance athletes count on electrolyte-rich sports drinks to get them through hours of training for the next triathlon or marathon. Research has shown that some of these drinks contain the right balance of nutrients and minerals to keep the energy level from flagging.

But a new study published in the January/February issue of General Dentistry shows that sipping certain sports drinks over long periods can wear down tooth enamel.

There haven't been a lot of previous studies on the subject. A study published in 2002 showed that there was no link between dental erosion and consuming sports drinks.

Here's how scientists at the University of Maryland Dental School arrived at their findings:

Researchers led by J. Anthony von Fraunhofer, professor of biomaterials science, used cavity-free teeth that were extracted for orthodontic or periodontal reasons. The teeth were sterilized, then enamel walls were cut into blocks. These blocks were soaked in screw-cap plastic containers filled with one of several beverages, including sports drinks, soda, energy drinks, iced tea and other sweetened drinks.

The sports drinks chosen were AMP energy drink, Gatorade lemon-lime, KMX energy drink and Powerade Arctic Shatter.

Researchers weighed the enamel blocks at 24- to 48-hour intervals for 14 days, measuring for weight loss. The exposure time of two weeks was comparable to about 13 years of normal beverage consumption.

They found that the enamel dissolution was significant for AMP, Powerade, Gatorade and KMX.

What's the culprit?

Von Fraunhofer said additives and organic acids are to blame. These can break down calcium and erode enamel.

The researchers say that their study may be criticized for the long exposure time and small sample size. And in reality, athletes will sip drinks for several hours, but not for 14 straight days. In between training sessions, they drink water and brush their teeth, so it's reasonable to suggest that those two practices may mitigate enamel damage.

Bruce DeGinder, president-elect and spokesman for the Academy of General Dentistry, issued this statement regarding the study: "We recommend altering or limiting the intake of soda and sports drinks and choosing water or low-fat milk instead, to preserve tooth enamel and ultimately protect teeth from decay."

But Von Fraunhofer has a different take for athletes: "I'm not suggesting that athletes give up their sports drinks."

Drink the liquid quickly - don't let the sports drink linger or sit in your mouth, he said. Alternate with sips of water to wash down some of the caustic acids.

And don't rush to brush your teeth right after a consuming a bottle or two of sports drinks, because that would exacerbate enamel damage. Rinse your teeth with water, then wait for at least half an hour or so before brushing.

Lisa Liddane is a health and fitness writer for The Orange County Register and an American Council on Exercise-certified group fitness instructor. Write to her at the Register, P.O. Box 11626, Santa Ana, Calif. 92711 or send e-mail to lliddanecregister.com.