title: Dietary vitamin C intake protects against COPD: the Korea National Health and Nutrition Examination Survey in 2012.
abstract: BACKGROUND
  Vitamin C, as an antioxidant, has recently been suggested to provide protection against COPD; however, only few national cohort studies have investigated these effects. We aimed to confirm the protective effects of vitamin C against COPD in Korean patients.
  
  
  METHODS
  We analyzed the data of 3,283 adults aged ≥40 years (representing 23,541,704 subjects) who underwent pulmonary function tests and responded to questionnaires on smoking history and vitamin C intake, with stratification variables and sampling weight designated by the Korea 2012 National Health and Nutrition Examination Survey.
  
  
  RESULTS
  Among all the subjects, 512 (representing 3,459,679 subjects; 15.6%) were diagnosed as having COPD based on pulmonary function test results. Male gender, old age, residence in suburban/rural regions, low household income, low educational level, an occupation in agriculture or fisheries, and heavy smoking were significantly associated with COPD. Low intake of nutrients, including potassium, vitamin A, carotene, retinol, and vitamin C, was significantly associated with COPD. The prevalence of COPD in heavy smokers with the lowest quartile (Q1, <48.50 mg; 63.0%) and low-middle quartile (Q2, 48.50-84.38 mg; 56.4%) of vitamin C intake was significantly higher than that in subjects with the high-middle quartile (Q3, 84.38-141.63 mg; 29.5%) and highest quartile (Q4, >141.63 mg; 32.6%) of vitamin C intake (P=0.015). In multivariate analysis, male gender, old age, heavy smoking, and a low intake of vitamin C were significant independent risk factors for COPD. A significant reduction of 76.7% in COPD risk was observed with a Q3 vitamin C intake compared to Q1 vitamin C intake (odds ratio, 0.233; 95% confidence interval, 0.094-0.576) in heavy smokers.
  
  
  CONCLUSIONS
  This large-scale national study suggests that dietary vitamin C provides protection against COPD, independent of smoking history, in the general Korean population.
authors.affiliation: Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine.
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine.
authors.forename: Min Kwang
authors.initials: MK
authors.lastname: Byun
authors.affiliation: Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine.
authors.forename: Hyung Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul.
authors.forename: Jae Yeol
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Chonnam National University Hospital, Gwangju.
authors.forename: Yu-Il
authors.initials: YI
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Konkuk University School of Medicine.
authors.forename: Kwang-Ha
authors.initials: KH
authors.lastname: Yoo
authors.affiliation: Department of Internal Medicine, Ewha Womans University School of Medicine.
authors.forename: Eun Mi
authors.initials: EM
authors.lastname: Chun
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Institute of Chest Disease, Severance Hospital, Yonsei University College of Medicine.
authors.forename: Ji Ye
authors.initials: JY
authors.lastname: Jung
authors.affiliation: Division of Pulmonology, Critical Care and Sleep Medicine, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Sang Haak
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine.
authors.forename: Chul Min
authors.initials: CM
authors.lastname: Ahn
mesh_terms: D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage*; D016009:Chi-Square Distribution; D004032:Diet; D005260:Female; D006304:Health Status; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009749:Nutrition Surveys; D016017:Odds Ratio; D015995:Prevalence; D065840:Protective Factors; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D056910:Republic of Korea / Q000453:epidemiology; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D013997:Time Factors
chemical_list: D001205:Ascorbic Acid
keywords: chronic obstructive lung disease; nutrition; risk factor; smoking; vitamin C