Low Intake of Vitamins A and C May Increase Risk of Asthma
New findings contradict those of large study published last year
FRIDAY, May 8 (HealthDay News) -- Low dietary intake of vitamins A and C is associated with higher odds of asthma, according to a study published online on April 30 in Thorax which contradicts the findings of a large study published last year.
Sarah Allen and colleagues at the University of Nottingham in the United Kingdom conducted a meta-analysis of 40 studies of asthma, wheeze or airway responsiveness relative to dietary or serum levels of vitamins A, C and E.
Three of the studies showed an association between asthma and dietary intake of vitamin A, while two showed an association between dietary intake of vitamin A and severity of asthma, the researchers found. In all, nine studies showed an association between the odds of asthma and intake of vitamin C but there was no evidence on a link between vitamin E intake and risk of asthma, the investigators noted. The authors assert that their study was conducted with higher methodological vigor than that of a recent review which came up with conflicting results.
"Epidemiological studies and meta-analyses are useful for identifying association between exposures and diseases but cannot reliably establish causation," the authors write. "Further investigations are necessary to account for the observed associations using well-designed randomized controlled trials of vitamin supplementation in asthma."