Supplement could fight cystic fibrosis.

Preliminary studies in mice suggest that a common dietary supplement might ward off the debilitating effects of cystic fibrosis, a genetic disease marked by life-threatening accumulations of mucus in the lungs.

Using mice carrying the genetic defect that causes the disease in people, Boston researchers showed that cell membranes in the lungs, pancreas, and intestines--the organs most affected by cystic fibrosis in people--have abnormally low levels of a fatty acid called docosahexaenoic acid (DHA). Feeding the mice large doses of DHA for a week not only corrected the imbalance but also reversed signs of the disease, Juan G. Alvarez and his colleagues at Beth Israel Deaconess Medical Center reported in Seattle last month at the Cystic Fibrosis Foundation's annual meeting.

To examine the human respiratory and digestive tracts, the researchers took nasal and rectal samples. Their preliminary evidence shows lower DHA concentrations in cells of the six people with the disease than in those of six healthy volunteers.

Trials in which people with cystic fibrosis will receive DHA as a dietary supplement are slated to begin as early as next year. Meanwhile, researchers are warning people with cystic fibrosis not to start taking supplements, such as fish oil, that are rich in DHA. Other components of the supplements might harm people with the disease, say the researchers.

DHA caused no obvious side effects in the mice. "So, the treatment should be sale in humans, but we don't know that for sure," cautions Steven D. Freedman of Beth Israel.

Decreases in DHA concentration in cell membranes tend to translate into increases in a fatty acid called arachidonic acid. This compound promotes inflammation and immune responses, reactions that are overactive in people with cystic fibrosis. The researchers propose that the imbalance between these two compounds is the source of characteristic symptoms such as chronic lung inflammation and excess mucus.

Unlike most cystic fibrosis drugs under development, DHA could be taken orally to treat disease symptoms throughout the body, not just in the lungs.