Researchers at the Children's Hospital & Research Center at Oakland in California, US, say their findings are a first step toward evaluation of vitamin C as therapeutic agent in the complementary treatment of asthma, cystic fibrosis and chronic obstructive lung disease.
The vitamin may even help alleviate the dry cough suffered by smokers.
In a two-year study, published in the 9 March issue of the Proceedings of the National Academy of Sciences (101(10):3691-6), the Children's researchers tested vitamin C on the function of a cell protein called the cystic fibrosis transmembrane conductance regulator (CFTR), which regulates secretion of fluids from the airway surfaces.
Vitamin C induced the openings of CFTR Cl channels and this extra exposure of the airway surface to vitamin C stimulated the secretion of fluids.The researchers said that vitamin C supports the normal hydration of airway surfaces, while vitamin C deficiency may lead to dry, sticky mucus membranes lining the airway.
"When the airway is not sufficiently hydrated, it becomes susceptible to infections, which may eventually cause asthma attacks in asthmatics," said lead researcher Beate Illek. ,i>"Increased intake of vitamin C may loosen those sticky airway secretions and improve clearance in the respiratory tract."
The findings of cellular testing were confirmed by instilling vitamin C into the nasal passages of healthy human subjects. The results suggest that supplemental vitamin C may improve airway symptoms, pending further clinical trials.
"Vitamin C may prove to be an effective, safe and low-cost treatment to improve current therapies, including bronchodilators, anti-inflammatory medications and antibiotics," said Illek.
Low levels of vitamin C may play a role in the progression of common inflammatory airway diseases.