Dietary supplementation with fish oil or olive oil and respiratory and cardiovascular effects of exposure to ozone in human subjects
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Exposure to air pollution, including ozone (O3), has been associated with increased respiratory and cardiovascular morbidity and mortality. Dietary supplementation with fish oil or olive oil has shown respiratory and cardiovascular benefits among people who were exposed to air pollutants. This controlled human exposure study aims to investigate the role of mono- or polyunsaturated fatty acids in modulating O3-induced effects in healthy volunteers.
After a 2-week period of dietary restrictions, 43 healthy subjects (18-35 years old) were randomized and double-blind to receive control (n=12, F:M = 6:6), 3 g fish oil (> 60% eicosapentaenoic acid / docosahexaenoic acid (EPA/DHA)) (n=15, F:M = 8:7), or 3 g olive oil (cold pressed extra virgin olive oil) (n=16, F:M = 6:10) per day for 4 weeks. Each subject was then exposed to filtered air and 300 ppb O3 with intermittent moderate exercise that targeting inspired ventilation rate at 20 L/min/m2 body surface area for 2 hours in two consecutive days. Pulmonary function, airway inflammation, endothelial function, and plasma lipid markers were measured pre – and post – exposure, and on the follow-up day.
Compared with control and olive oil, fish oil supplementation significantly increased blood omega-3 index, EPA and DHA levels, and decreased the ratio of omega-6/omega-3 and triglycerides. O3 exposure significantly decreased pulmonary function (force vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC) while supplementation of fish oil, but not olive oil, blunted the drop of FEV1 and FEV1/FVC. Percent of polymorphonuclear neutrophil (PMN%) in airway sputum was significantly increased by ozone exposure, but neither fish oil nor olive oil supplementation significantly modified the increase. The diameter of retinal blood vessels was not affected by the O3 exposure or the dietary supplements.
In summary, dietary supplementation with fish oil was effective in blunting pulmonary function decrements but not the airway inflammatory response induced by exposure of young healthy volunteers to O3. These findings suggest insights on the mechanistic basis for the health effects of O3 exposure and a potential interventional approach to mitigating its effects.