title: Dietary folate and the risk of nonfatal myocardial infarction.
abstract: BACKGROUND
  Elevated homocysteine levels have been associated with a higher risk of cardiovascular disease. Because folate intake can reduce homocysteine levels, we investigated the association between dietary folate intake and nonfatal myocardial infarction.
  
  
  METHODS
  We conducted a case-control study in three tertiary hospitals of Pamplona, Spain, between 1999 and 2001. Study physicians enrolled 171 patients less than 80 years of age with a first nonfatal myocardial infarction and 171 control patients matched by age, sex, hospital and calendar month. We excluded patients with any prior major cardiovascular disease. Participants were interviewed about medical factors and life-style and completed a food frequency questionnaire previously validated in Spain. We calculated energy-adjusted intakes of folate and estimated relative risks (RRs) of myocardial infarction and 95% confidence intervals (CIs) using conditional logistic regression. Relative risks were adjusted for conventional risk factors.
  
  
  RESULTS
  Only 6% of participants were taking vitamin supplements. The main sources of folate were green leafy vegetables, green beans, oranges, peppers and lettuces. The estimated matched RR of myocardial infarction for the top three quartiles of folate intake (, above 340 microg/day) was 0.57 (CI = 0.35-0.94), compared with the lowest quartile of intake. The multivariate adjusted RR was 0.51 (CI = 0.24-1.06). There was no apparent dose effect above this threshold.
  
  
  CONCLUSIONS
  Our results in a Mediterranean population with natural plant foods as the main source of folate provide further evidence to support the hypothesis that dietary folate intake may be an independent protective factor for myocardial infarction. The magnitude of the effect, its biological plausibility, and the consistency across studies offer support for a causal association.
authors.affiliation: Slone Epidemiology Center, Boston University School of Public Health, Boston, MA 02215, USA. sherman@bu.edu
authors.forename: Sonia
authors.initials: S
authors.lastname: Hernández-Díaz
authors.forename: Ernesto
authors.initials: E
authors.lastname: Martínez-Losa
authors.forename: Elena
authors.initials: E
authors.lastname: Fernández-Jarne
authors.forename: Manuel
authors.initials: M
authors.lastname: Serrano-Martínez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Martínez-González
mesh_terms: D016022:Case-Control Studies; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008522:Mediterranean Sea; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology* / Q000517:prevention & control*; D009749:Nutrition Surveys; D016017:Odds Ratio; D012306:Risk; D013030:Spain / Q000453:epidemiology; D013997:Time Factors
chemical_list: D005492:Folic Acid