Folate intake associated with lung function, breathlessness and the prevalence of chronic obstructive pulmonary disease.

A case-control study was conducted in central Japan to investigate the relationship between dietary intake of folate and lung function, breathlessness and chronic obstructive pulmonary disease (COPD). A total of 278 referred patients (244 men and 34 women) aged 50-75 years with COPD diagnosed within the past four years and 340 community-based controls (272 men and 68 women) were assessed for dyspnoea and undertook spirometric measurements of lung function. A structured questionnaire was administered face-to-face to obtain information on demographics, lifestyle and habitual food consumption. Folate intake was derived from the Japanese food composition tables. The COPD patients had significantly lower habitual intake of folate (mean 231, SD 90 microg/day) than control subjects (mean 261, SD 110 microg/day), p<0.001. Lung function measures were found to be positively associated with dietary folate level. Reductions in prevalence of COPD and especially breathlessness were observed, the respective adjusted odds ratio (OR) being 0.74 (95% confidence interval (CI) 0.35 to 1.58) and 0.43 (95% CI 0.21 to 0.91) for the highest versus lowest quartile of folate intake. The corresponding tests for linear trend were also significant (p<0.05). In conclusion, an inverse association was evident between dietary folate intake and the prevalence of breathlessness for Japanese adults, together with a significant dose-response relationship for the COPD risk. Moreover, increased folate intake might be beneficial to lung function.