A combination of antioxidants was found to protect the lungs of healthy volunteers against damage by ozone, a pollutant found in smog. The study, published this week in the American Journal of Respiratory Care and Critical Care Medicine,(1) found that the antioxidant combination preserved lung function in individuals subjected to controlled ozone inhalation.
Previous studies have demonstrated protective effects of antioxidant supplements against ozone-induced lung damage.(2,3,4) Taken together with the new study, the evidence now appears strong that nonsmokers living and exercising in polluted areas should consider antioxidant supplementation as a way to protect their lungs.
The presence of ozone in the lowest layer of the earth's atmosphere (the troposphere) is a major public health problem. It is estimated that more than 130 million Americans live in areas where ozone levels exceed the National Ambient Air Quality Standard of 80 parts per billion, which should not be exceeded more than three times per year.(5) Exposure to ozone is known to cause impairments in lung function: notably, decreased breathing capacity, airway hyperreactivity, and inflammation of the air passages.
Thirty-one healthy, nonsmoking adults participated in the new study. They consumed a diet low in vitamin C for three weeks. After the first week, they were exposed to filtered air for two hours while exercising. Cell samples were then obtained from the lungs, through a washing procedure known as "bronchoalveolar lavage," to measure the degree of inflammation. Next, participants received either a placebo or a combination of vitamin C (250 mg per day), vitamin E (50 IU per day), and a vegetable cocktail (a source of carotenoids, primarily consisting of carrot and tomato juice, 12 ounces per day) for two weeks. Participants were then exposed to 0.4 parts per million of ozone for two hours and underwent a second bronchoalveolar lavage.
In addition to raising blood levels of the antioxidants, the combination supplement protected against the ozone-induced decline in lung function. On the other hand, the antioxidants did not reduce the degree of lung inflammation resulting from ozone exposure.
Antioxidants, particularly vitamin C, have also been found previously to preserve lung function in people with asthma. Supplementation with 1 gram of vitamin C per day reduces the tendency of the bronchial passages to go into spasm,(6) an action that has been confirmed in double-blind research.(7) In one double-blind trial, 500 mg of vitamin C per day for just two days prevented attacks of exercise-induced asthma.(8) However, other studies,(9) including two double-blind trials,(10,11) have failed to corroborate these findings.
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References:
1. Samet JM, Hatch GE, Horstman D, et al. Effect of antioxidant supplementation on ozone-induced lung injury in human subjects. Am J Respir Crit Care Med 2001;164:819-25.
2. Chatham MD, Eppler JH Jr, Sauder LR, et al. Evaluation of the effects of vitamin C on ozone-induced bronchoconstriction in normal subjects. Ann N Y Acad Sci 1987;498:269-79.
3. Grievink L, Jansen SM, van't Veer P, Brunekreef B. Acute effects of ozone on pulmonary function of cyclists receiving antioxidant supplements. Occup Environ Med 1998;55:13-7.
4. Grievink L, Zijlstra AG, Ke X, Brunekreef B. Double-blind intervention trial on modulation of ozone effects on pulmonary function by antioxidant supplements. Am J Epidemiol 1999;149:306-14.
5. Lippman M. Ozone. In: Rom WM, editor. Environmental and Occupational Medicine, 3rd ed. Philadelphia: Lippincott-Raven Publishers, 1988:601-15.
6. Zuskin E, Valic F, Bouhuys A. Byssinosis and airway responses due to exposure to textile dust. Lung 1976;154:17-24.
7. Bucca C, Rolla G, Oliva A, Farina J-C. Effect of vitamin C on histamine bronchial responsiveness of patients with allergic rhinitis. Ann Allergy 1990;65:311-4.
8. Schachter EN, Schlesinger A. The attenuation of exercise-induced bronchospasm by ascorbic acid. Ann Allergy 1982;49:146-51.
9. Ting S, Mansfield LE, Yarbrough J. Effects of ascorbic acid on pulmonary functions in mild asthma. J Asthma 1983;20:39-42.
10. Malo JL, Cartier A, Pineau L, et al. Lack of acute effects of ascorbic acid on spirometry and airway responsiveness to histamine in subjects with asthma. J Allergy Clin Immunol 1986;78:1153-8.
11. Kordansky DW, Rosenthal RR, Norman PS. The effect of vitamin C on antigen-induced bronchospasm. J Allergy Clin Immunol 1979;63:61-4