Chronic obstructive pulmonary disease (COPD) is a permanent lung condition caused, most often, by cigarette smoking. It starts with a wheezing cough and gradually progresses to a shortness of breath that accompanies even the slightest exertion, such as dressing or eating. COPD encompasses both emphysema and chronic bronchitis.

Emphysema consists of the destruction of the tiny air sacs (alveoli) in the lungs and the weakening of the support structure around them. This leads to a collapse of the small airways in the lungs, especially on inhalation, and reduces the body's ability to take in oxygen and expel carbon dioxide.

Chronic bronchitis consists of chronic inflammation of the airways, causing a persistent productive cough. This inflammation also impairs the body's ability to exchange new air for old. COPD also involves spasm of the airways similar to what occurs in asthma. Finally, occasional flare-ups occur when bacteria grow in the lungs, leading to acute exacerbation of symptoms.

Because cigarette smoking contributes to both emphysema and chronic bronchitis, anyone who has COPD should stop smoking. Quitting smoking won't reverse the condition, but it might stop COPD from getting worse. Airborne irritants such as chemical fumes exacerbate symptoms and should also be avoided. Standard treatment for COPD includes using bronchodilators, such as ipratropium and albuterol, to reduce muscle spasms, and corticosteroids to control inflammation in the airways. Acute flare-ups are treated with antibiotics. Severe COPD may require continuous oxygen therapy.

Malnutrition is common among people with COPD and seems to correspond to the severity of the condition.1,2It's been suggested that the caloric needs of people with COPD increase as the disease progresses.3Because malnutrition in turn can worsen lung function and make people more prone to infection, many researchers now recommend that individuals with COPD receive supplemental nutrition as part of their treatment.4,5

N-acetyl cysteine (NAC) may improve breathing in people with COPD.

NAC is a specially modified form of the dietary amino acid cysteine. Regular use of NAC may diminish the number of severe bronchitis attacks. A review and meta-analysis of available research focused on 8 reasonably well-designed double-blind, placebo-controlled trialsof NAC in COPD.7-15The results of these studies, involving a total of about 1,400 individuals, suggest that NAC taken daily at a dose of 400 to 1,200 mg can reduce the number of acute attacks of severe bronchitis. However, a subsequent 3-year, double-blind, placebo-controlled study of 523 people with COPD failed to find benefit with 600 mg of NAC daily.35

NAC was once thought to aid lung conditions by helping to break up mucus. However, continuing research has tended to cast doubt on this explanation of its action.

For more information, including dosage and safety issues, see the full NAC article.