Table 1.
Studies assessing effect of antioxidant supplementation on lung function associated with controlled air pollutant exposures in intact humans
| First author, Year, Country | Study design | Conditions* | Pollutant exposure duration | Additional stresses during exposure | Population (N) |
Age range | Inclusion / Exclusion criteria | Outcome |
|---|---|---|---|---|---|---|---|---|
| Hackney, 1981, USA | Randomized (non-crossover); supplement double-blinded; exposure nominally single-blinded |
a) 800 IU Vitamin E (9 to 10 weeks); air then next-day ozone (0.5 ppm) | 2 hr | Heat and "light exercise" | Healthy (34) |
20-27 | Not Specified. | No significant effect of antioxidants on ozone-attributable decrease in FEV1 and FVC. (i.e. statistical significance of supplementation effect: p > 0.05). |
| b) Placebo (9 to 10 weeks);air then next day ozone (0.5 ppm) | ||||||||
| Hackney, 1981, USA | Randomized (non-crossover); supplement double-blinded, exposure nominally single-blinded |
a) 1600 IU Vitamin E (11 to 12 weeks); air then ozone (0.5 ppm, for 2 subsequent days) | 2 hr | Heat and "light exercise" | Healthy males (22) |
22-28 | Not Specified. | No significant effect of antioxidants on ozone-attributable decrease in FEV1, FVC, TLC, FEF25%, FEF50% (i.e. statistical significance of supplementation effect: p > 0.05). |
| b) Placebo (11 to 12 weeks); air then ozone (0.5 ppm, for 2 subsequent days) |
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| Chatham, 1987, USA | Randomized (crossover); double-blinded | a) Vitamin C (1 gm, one hour before exposure) and Vitamin E (800 IU daily for unspecified duration); ozone (0.3 ppm) | 2 hr | Exercise | Medical students (9) |
21-29 | Normal baseline pulmonary function, non-smokers, refrained from any drugs, including vitamin supplements. | Ozone-induced decrements in FVC were attenuated by vitamin C and vitamin E (p < 0.05), but no significant effect was observed in FEV1, FEF25-75 and SGaw (p > 0.05). |
| b) Placebo; Ozone (0.3 ppm) | ||||||||
| Mohensin, 1987, USA | Randomized (crossover); double-blinded | a) Vitamin C (2000 mg/day for 3 days); NO2 (2.0 ppm) | 1 hr | Healthy subjects (11) |
18-36 | Not Specified. | Airway hypersensitivity induced by NO2 was attenuated by pre-treatment with ascorbic acid, relative to placebo (p < 0.04). | |
| b) Placebo (3 days); NO2 (2.0 ppm) | ||||||||
| c) Vitamin C (2000 mg/day for 3 days); air | ||||||||
| d) Placebo; air | ||||||||
|
Peters, 2001, The Netherlands |
Double-blinded; cross over; |
a) Placebo; ozone (0.4 ppm) | 2 hr | Intermittent exercise | Mild atopic asthmatics (7) |
19-26 | Required a measurable plateau of the dose-response curve to methacholine, non smokers, no NSAID or vitamin use during study. | Airway hypersensitivity induced by O3 was attenuated by pre-treatment with apocynin, relative to placebo (p = 0.025). |
| b) Apocynin (12 mg); ozone (0.4 ppm) | ||||||||
| Samet, 2001, USA | Randomized (non-crossover); double-blinded |
a) Vitamin C-restricted diet + placebo (2 weeks); ozone (0.4 ppm) | 2 hr | Exercise | Healthy on a low ascorbate diet (31) |
18-35 | Non-smokers. | Ozone-induced decrements in FEV1 and FVC were attenuated (p = 0.046 and p = 0.055 respectively), by vitamin C and vitamin E. |
| b) Vitamin C-restricted diet + 250 mg of vitamin C, 50 IU of alpha-tocopherol, and 12 oz. of vegetable cocktail (2 weeks); ozone (0.4 ppm) |
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| c) Vitamin C-restricted diet (1 week); air |
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| Trenga, 2001, USA | Randomized (crossover); double-blinded |
a) Placebo; ozone (0.12 ppm) | 45 min | Intermittent exercise | Adults with asthma (17) |
18-39 | Significant decrease (at least 8%) in FVC1 from baseline with SO2 challenge, non-smokers. | SO2-induced decrements in FEV1 and peak expiratory flow (PEF), and FEF25-75 were attenuated by vitamin C and vitamin E (p < 0.05). |
| b) 400 IU vitamin E and 500 mg Vitamin C daily (4 weeks); ozone (0.12 ppm) |
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| c) Placebo; air | ||||||||
| d) 400 IU Vitamin E and 500 mg Vitamin C daily (4 weeks); air | ||||||||
| Mudway, 2006, Sweden | Randomized (crossover); double-blinded |
a) Placebo; ozone (0.2 ppm) | 2 hr | Intermittent exercise | Healthy ozone-sensitive (14) |
21-27 | Normal lung function, negative skin prick test, non-smokers, no history of allergy and/or lung disease. | No significant effect of antioxidants on ozone-attributable decrease in FEV1 (p > 0.05). |
| b) 500 mg Vitamin C with 100 mg Vitamin E (7 days); ozone (0.2 ppm) |
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| c) air |
* For crossover studies, each individual subjected to each condition; in non-crossover, the conditions were distributed between subjects.