Protection may be in sight for travelers who frequently face a common type of diarrhea known as "Montezuma's revenge."

A new kind of powdered milk showed promise in a study released Wednesday for protecting people from most cases of the gastrointestinal problem, which is also known as "traveler's diarrhea.""This material is very effective in preventing the diarrhea," said Dr. Carol O. Tacket, an assistant professor of medicine at the University of Maryland School of Medicine in Baltimore who headed the study.

The milk contains antibodies that can kill a type of bacterium known as Escherichia coli, which causes most cases of the diarrhea, she said.

About half of all people who travel to underdeveloped countries that have poor sanitation are estimated to experience the diarrhea after being exposed to the bacteria.

Antibiotics or Pepto-Bismol can prevent the diarrhea. But antibiotics can cause side effects, and using large amounts of antibiotics can make them ineffective later when they may be needed for more severe illness. Too much Pepto-Bismol can also have side effects, she said.

The new approach is called bovine milk immunoglobulin concentrate.