The results from three recent Western studies also suggest that vitamin C may lower the risk of obstructive emphysema, chronic bronchitis, and other forms of chronic lung disease. COPD is a major cause of death and disability in the US and other countries.

Smoking greatly increases the risk of COPD. Since only about 15% of smokers develop the disease, however, other factors also appear to come into play. Individuals who consumed a diet rich in vitamin C and who had relatively high levels of the vitamin in their blood, had better lung function, and consequently, a lower risk of COPD than those with lower intakes and blood levels of the vitamin, the researchers found.

The investigators found that the higher the intake of vitamin C, the better the lung function. Those in the study averaged about 151 milligrams of vitamin C per day, about 50% more than the US average. The US Department of Agriculture suggests that most adults consume 60 mg of the vitamin daily. Why vitamin C appears to lower risk of COPD is not entirely clear either, the researchers note.

One possibility is that the vitamin, an antioxidant, protects the lungs from the actions of free radicals -- harmful byproducts of breathing and other metabolic processes that can damage cells. But antioxidants can "mop up" free radicals, thus preventing their negative effects. There is also some evidence that vitamin C may protect the airways through improved immune function.

American Journal of Epidemiology October, 1998;148:594-599.

Dr. Mercola's Comment:

I suspect the ideal dose of vitamin C for most people is much higher than 151 mg per day. Some people may need 100 mg per day while some may benefit from 100 grams per day. Vitamin C is short-lived so one should take it at least two or three times per day in divided doses.

When one exceeds the amount one requires, there is a tendency to develop loose stools. So if you are taking high doses of vitamin C and have loose stools, you should reduce your dose. The other concern with higher doses is that unless it is a buffered vitamin C it will tend to cause mineral depletion.