Little-known vitamins present in orange, red, green and yellow fruit and vegetables can help improve lung health, according to recent research from the University at Buffalo in the US.
Writing in the 1 March issue of the American Journal of Epidemiology, the UB researchers said that the antioxidants lutein and zeaxanthin, members of the carotenoid family, can have a significant positive effect on lung health, reducing the ageing effect by as much as one to two years.
Green leafy vegetables such as spinach, kale and collard greens are good sources of lutein and zeaxanthin.
The team also found evidence to confirm their earlier findings that dietary intake of food containing vitamins C and E could also improve lung function. In a study published last May, they reported that high blood levels of vitamins C and E and the carotenoids lutein, zeaxanthin and beta-cryptoxanthin were associated with better pulmonary function in a general population.
"The importance of this study is that it strengthens the hypothesis that carotenoids are antioxidant vitamins that play a significant role in maintaining respiratory function, and that beta-carotene may not be the 'one' important carotenoid," said Dr Holger Schunemann, UB assistant professor of medicine and social and preventive medicine and lead author on the study.
"Impaired lung function is associated with an increased risk of dying, so it is important to determine the factors that could influence lung function," he said. "This information may be even more important for smokers, who have a heavy free radical burden." Antioxidants such as carotenoids attack the harmful free radicals produced by the body.
Dr Schunemann's study was based on dietary records and interviews obtained from 1,616 randomly selected residents of western New York, aged 35 to 79, who were free of respiratory disease. All participants performed standard lung-function tests, which measured the volume of air they could expel in one breath - forced vital capacity (FVC) - and the volume forcibly expelled in one second (FEV1).
While lutein and zeaxanthin showed the strongest association with pulmonary function, the results also showed that vitamins C and E had a positive effect on lung health.
"But when we considered these antioxidant vitamins simultaneously, only vitamin E correlated significantly with FEV1 and only lutein and zeaxanthin with FEV," Dr Schunemann said. Taking vitamin C and E supplements did not change the results significantly.
"Further studies are needed to confirm these results, and longitudinal studies could help to clarify whether this association is related to lung development in childhood and adolescence, or whether it's the result of an accumulation of protective effects against oxidative damage throughout life."