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Table 1 Studies assessing effect of antioxidant supplementation on lung function associated with controlled air pollutant exposures in intact humans

From: Modification by antioxidant supplementation of changes in human lung function associated with air pollutant exposure: A systematic review

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)

      

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)

      
  

c) Vitamin C-restricted diet

(1 week); air

      

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)

      
  

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)

      
  

c) air

      
  1. * For crossover studies, each individual subjected to each condition; in non-crossover, the conditions were distributed between subjects.