Dietary supplement helps lung function in cystic fibrosis patients, Stanford/Packard study finds


Life expectancy for people with cystic fibrosis has improved dramatically in the last few decades, but those with CF still struggle with a very basic action: breathing easily. However, a new study indicates that a specific dietary supplement might stave off the decline in lung function that characterizes this genetic disease.

“CF is a disease that’s characterized by quite a bit of inflammation in the lungs,” said Carol Conrad, MD, who led a recent scientific study that tested the effect of a specific dietary supplement on lung function in CF patients. Conrad directs both the Pediatric Pulmonary Function Lab and the Pediatric Lung Transplant Program at Lucile Packard Children’s Hospital Stanford, and does research on CF at the Stanford University School of Medicine.

The Phase II study tested the effects of n-acetylcysteine, or NAC, a dietary supplement thought to boost the body’s antioxidant stores. The supplement improved patients’ lung function, but not in the way the research team expected.

Here’s what the researchers thought would happen: They knew that CF patients have a lot of white blood cells – our bodies’ infection fighters – in their lungs, and that inflammation is a damaging side effect of the cells’ work to fight pathogens. The body’s natural antioxidants, including a molecule called glutathione, are supposed to keep inflammation in check. But CF patients have low glutathione levels.

“Our theory was that if we could give them a dietary supplement that would help them rebuild normal stores of this antioxidant, that might calm down the inflammation going on in their lungs,” Conrad said. “We hoped that would improve their lung function and their overall quality of life.”

The study, of 70 cystic fibrosis patients aged 9 to 59 who were randomly assigned to take either NAC or a placebo three times daily, showed no differences between the groups on several measures of inflammation and antioxidant status.

However, the patients getting NAC maintained their lung function over the 6-month study, while the patients receiving the placebo experienced a decline in lung function. CF patients typically experience gradually declining lung function, so the possibility that a dietary supplement could slow or avert this deterioration is great news.

“We didn’t expect to see lung function differences between the two groups,” Conrad said. “The fact that we actually saw them is incredibly interesting and exciting. This was consistent across all measures of lung function, so it’s not a fluke, but it was apparently happening via a different pathway than we expected.”

The team plans to conduct larger and longer studies to examine how NAC works in people with CF. The supplement has a good safety profile, but the frequent doses used in the research are challenging for patients to take consistently. Doctors need a better understanding of how the supplement works and how much is needed to make a difference for patients before they recommend it widely, Conrad said.

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4 Responses to “Dietary supplement helps lung function in cystic fibrosis patients, Stanford/Packard study finds”

  1. Monica

    Is there public access to the results of this study on NAC so that age-appropriate dosing amounts might be spoken about between patients and their providers?

    Thank you!

  2. Karina Gilkerson

    I would like to know if there has been any follow up research on this subject, and also if there have been any studies on the usefulness of NAC for digestive problems.

  3. Marcella Clancy

    Been using NAC for a few years – son 18 with CF. Definitely helps. What doses were used during the study please?

  4. Douglas Younkin

    This appears to be the Phase II trial report:


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