"The curiosity is definitely there," says Cleveland Clinic pulmonologist Umur Hatipoglu, MD. "And there is pretty convincing emerging data that we should look into."
Of the many remedies touted for COPD, N-acetylcysteine (NAC), ginseng, and vitamin D "are the three big ones," says naturopathic physician Jeremy Mikolai, ND, a researcher at the National College of Natural Medicine in Portland, Ore.
NAC is an antioxidant supplement that has shown promise in some studies but not in others.
"NAC is a robust treatment for COPD that reduces phlegm and cough, thins mucus, and eases expectoration," says Mikolai. It's said to decrease the deterioration of lung function. However, the evidence to support that claim is weak, according to a research review done in 2006 on how NAC affects COPD. That review said the design of the study in question did not allow for "firm conclusions."
Meanwhile, a large, three-year research project known as the BRONCUS study found that NAC did not prevent decline in lung function.
The BRONCUS study also looked at NAC from another angle. Could the supplement, the authors asked, cut the number of COPD flare-ups people get in a given year?
The authors report that NAC did not prevent flare-ups, but additional analysis suggested that the rate of flare-ups might be less in people not taking an inhaled steroid.
Despite that limited positive result, Hatipoglu says, NAC was "almost buried for dead after that study."
Still, he does often recommend NAC for its ability to loosen sputum, although its effectiveness hasn't been fully established.
"If my patients say they are doing better on it, I keep them on it," says Hatipoglu, who adds that NAC is quite safe. Though NAC is safe, it does contain sulfur, which gives it an odor "like rotten eggs," he says. In the BRONCUS study, researchers reported no side effects from NAC use.
Duffy MacKay, ND, says that he found NAC, which can also be inhaled via a nebulizer, to be similarly effective in his practice.
"The constant buildup of mucus -- that's where NAC seems to be most active," says MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a trade group that represents the dietary supplement industry.