Researchers from Imperial College in London looked at patients with asthma or chronic obstructive pulmonary disease (COPD), and found that those with low levels of vitamin C had an increased risk of breathing problems when outdoor air pollution levels were high, MyHealthNewsDaily reported.
"The protective effect of vitamin C was still present after excluding smokers and elderly subjects, implying that the effect of this antioxidant was not explained by smoking or age," study researcher Cristina Canova said.
Antioxidants, such as vitamin C, may protect the body from harmful molecules called free radicals that damage cells. Free radicals can form when air pollution enters the lungs, and evidence suggests they play a role in heart disease, cancer and even respiratory ailments.
Antioxidants can bind to free radicals, counteracting them before they damage cells.
Researchers looked at more than 200 patients admitted to the hospital for asthma or COPD, along with the levels of air pollution on the days before and after they entered the hospital.
The majority of patients were between ages 54 and 74, though some were as young as 18. Many of them were former smokers.
Specifically, the researchers looked at levels of "course particulate matter", which is produced largely through the combustion of fossil fuels.
Results showed that with every increase in course particulate matter of 10 microgrammes per cubic metre (mcg/m3), there was a 35 per cent increased risk of hospital admission for people with asthma or COPD.
However, the risk of admission was 1.2 times greater among people with low levels of vitamin C.
"It is certainly biologically plausible that vitamin C, which acts as an antioxidant, could protect against the effects of air pollution," Patrick Ryan, an epidemiologist at the Cincinnati Children's Hospital Medical Center was quoted as saying by the website.
Since the study participants had either asthma or COPD, it's not clear whether vitamin C would benefit people without these ailments.
The study was published in the journal Epidemiology.