Struggling to survive three years of food shortages by eating grass, bark and roots, North Koreans are developing stomach diseases, an aid official said Tuesday.

Months of meager government food rations and, in some places, a complete lack of food have forced many North Koreans to scrounge for anything to eat, said Kathi Zellweger, who left the communist country early Tuesday.During a weeklong tour of aid programs, Zellweger found that water is scarce and tainted from last year's drought, hospitals have little medicine and doctors reported an increase in diarrhea and stomach ailments.

"This is more of a problem because they are trying to produce food out of everything that is edible - herbs, grass, roots, anything," said Zellweger.

On her last trip in May, she took samples of the alternative foods and had them analyzed.

"The results were shocking," she said. "The human body is just not capable of digesting this kind of food."

North Korean officials, working with U.N. experts, have estimated that at least $300 million in aid would be needed for the next three years.