The genetic disease, which affects 30,000 American children and young adults, attacks patients' lungs with a thick mucus and most die from lung damage or infection.
The researchers - Dr. Juan Alvarez and Dr. Steven Freedman of Beth Israel Deaconess Medical Center in Boston - worked with mice genetically altered to mimic cystic fibrosis.
They found the altered mice had abnormally high levels of one fatty acid - arachidonic acid, or AA - and abnormally low levels of another - docosahexaeonic acid, or DHA. The imbalance was limited to the organs most affected by cystic fibrosis, including the lungs, pancreas and intestines.
When the altered mice were fed large doses of DHA for one week, the researchers reported, not only was that imbalance corrected - the signs of cystic fibrosis also were reversed.
Preliminary tests suggest the imbalance involving the two fatty acids also exists in people with the disease, Alvarez and Freedman said. They are studying the relationship in cystic fibrosis patients under a research agreement with Genzyme General of Cambridge, Mass.
"Although a number of steps remain before the benefit of DHA to patients is known, this exciting research presents an entirely new strategy to correct and possibly even prevent some of the ravages of this disease," said Robert J. Beall, president and chief executive officer of the Cystic Fibrosis Foundation.
DHA is available as a nutritional supplement in health food stores, but the researchers and foundation officials warned patients against experimenting at home.
Clinical trials are expected to begin next year.
"They've made some tantalizing observations in an animal model," said Dr. Peter Durie, director of cystic fibrosis research at the Hospital for Sick Children in Toronto, where the CF gene was discovered 10 years ago.
Cystic fibrosis is the most common fatal hereditary disease among Caucasians in the United States. The median life expectancy is 32 years. Treatments to fight lung infections and improve nutrition have improved care dramatically, but they treat only symptoms.
One cystic fibrosis patient was optimistic about the research.
"I think it's very promising," said Suzanne Pattee, an attorney at the Washington, D.C.-based CF Foundation. As for her illness, she said, "Obviously I'm more fortunate than many - I'm in my mid-30s."
By Peggy Andersen