Dietary intake of six minerals in relation to the risk of chronic obstructive pulmonary disease.

To investigate the relationship between dietary intake of minerals and the risk of chronic obstructive pulmonary disease (COPD), a case-control study was conducted in central Japan. 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 undertook spirometric measurements of lung function. A structured questionnaire was administered face-to-face to obtain information on demographics and habitual food consumption. Dietary intakes of six major minerals were derived from the Japanese food composition tables. The COPD patients had lower habitual energy-adjusted intakes of calcium, phosphorus and iron than controls, but not sodium. A significant reduction in prevalence of COPD was observed for calcium, with adjusted odds ratio 0.65 (95% confidence interval: 0.37- 0.98) for the highest level versus lowest level of intake. A high iron intake was also inversely associated with the COPD risk. In conclusion, an inverse association was evident between dietary calcium intake and the risk of COPD for Japanese adults.