LAUSR

BACKGROUND Combined atmospheric oxidant capacity (Ox), represented by the sum of nitrogen dioxide (NO2) and ozone (O3), is an important hazardous property of outdoor air pollution mixture. It remains unknown whether its adverse effects can be ameliorated by dietary fish-oil supplementation. OBJECTIVE To assess the effects of fish-oil supplementation against oxidative stress induced by acute Ox exposure. METHODS We conducted a randomized, double-blinded and placebo-controlled study among 65 young adults in Shanghai, China between September 2017 and January 2018. We randomly assigned participants to receive either 2.5 g/day of fish oil or placebo, and conducted four repeated physical examinations during the last two months of treatments. Ox concentrations were calculated as the sum of hourly measurements of NO2 and O3. We measured six biomarkers on systemic oxidative stress and antioxidant activity. Linear mixed-effect models were used to assess the short-term effects of Ox on biomarkers in each group. RESULTS During our study period, the 72-h average Ox concentration was 93.6 μg/m3. Short-term exposure to Ox led to weaker changes in all biomarkers in the fish oil group than in the placebo group. Compared with the placebo group, for a 10-μg/m3 increase in Ox, there were smaller decrements in myeloperoxidase (MPO, difference = 5.92%, lag = 0-2 d, p = 0.03) and malondialdehyde (MDA, difference = 5.00%, lag = 1 d, p = 0.04) in the fish-oil group; there were also larger increments in total antioxidant capacity (TAC, difference = 16.33%, lag = 2 d, p = 0.02) and in glutathione peroxidase (GSH-Px, difference = 8.89%, lag = 0-2 d, p = 0.03) in the fish-oil group. The estimated differences for MPO were robust to adjustment for all co-pollutants and the differences for other biomarkers remained for some co-pollutants. CONCLUSIONS This trial provides first-hand evidence that dietary fish-oil supplementation may alleviate the systemic oxidative stress induced by Ox.