Contrary to previous studies, giving patients with lung problems omega-3 fatty acids and “antioxidants”appears to do more harm than good, researchers reported Wednesday.

A study involving 272 adults who were being treated at 44 hospitals for acute lung problems failed to find any benefits and even indicated the treatment may worsen patients’ condition.

Previous research had found that lung patients had reduced levels of omega-3 fatty acids, which are thought to be beneficial by reducing inflammation, and three small clinical studies found that those who received the substances along with antioxidants fared better. But those studies were relatively small.

In the new study, patients received the substances twice daily within 48 hours of requiring mechanical ventilation. The study was terminated early after an interim analysis determined those getting the antioxidants ended up spending more days on a ventilator, more days in intensive care and may be more likely to die, the researchers reported in a paper published online in the Journal of the American Medical Association. The paper is to coincide with a presentation at the European Society of Intensive Care Medicine meeting in Berlin.

The patients receiving the omega-3 fatty acids and antioxidants had fewer days when they were able to get off the ventilator--14 vs 17.2--and had fewer days when they were able to get out of intensive care--14 vs 16.7. In addition, 38 of the 143 patients getting the treatment--26.6 percent--died, compared with 21 of the 129 patients who received placebo--16.3 percent. But that difference, while causing concern, was not considered statistically significant.

In an editorial accompanying the study, Deborah Cook of McMaster University Health Sciences Center and Daren Heyland of Queens University in Canada said the findings show that more research is needed to explore the safety and effectiveness of dietary supplements.

“Larger trials will help to inform practitioners regarding which interventions do more good than harm, which do more harm than good, and which truly have no effect,” they wrote.

The new study is far from the first time a dietary supplement that looked promising ended up producing disappointing results. Beta carotene supplements, for example, turned out to increase the risk for lung cancer for smokers (1994, 2004 studies).