title: Systematic evaluation of environmental factors: persistent pollutants and nutrients correlated with serum lipid levels.
abstract: BACKGROUND
  Both genetic and environmental factors contribute to triglyceride, low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C) levels. Although genome-wide association studies are currently testing the genetic factors systematically, testing and reporting one or a few factors at a time can lead to fragmented literature for environmental chemical factors. We screened for correlation between environmental factors and lipid levels, utilizing four independent surveys with information on 188 environmental factors from the Centers of Disease Control, National Health and Nutrition Examination Survey, collected between 1999 and 2006.
  
  
  METHODS
  We used linear regression to correlate each environmental chemical factor to triglycerides, LDL-C and HDL-C adjusting for age, age(2), sex, ethnicity, socio-economic status and body mass index. Final estimates were adjusted for waist circumference, diabetes status, blood pressure and survey. Multiple comparisons were controlled for by estimating the false discovery rate and significant findings were tentatively validated in an independent survey.
  
  
  RESULTS
  We identified and validated 29, 9 and 17 environmental factors correlated with triglycerides, LDL-C and HDL-C levels, respectively. Findings include hydrocarbons and nicotine associated with lower HDL-C and vitamin E (γ-tocopherol) associated with unfavourable lipid levels. Higher triglycerides and lower HDL-C were correlated with higher levels of fat-soluble contaminants (e.g. polychlorinated biphenyls and dibenzofurans). Nutrients and vitamin markers (e.g. vitamins B, D and carotenes), were associated with favourable triglyceride and HDL-C levels.
  
  
  CONCLUSIONS
  Our systematic association study has enabled us to postulate about broad environmental correlation to lipid levels. Although subject to confounding and reverse causality bias, these findings merit evaluation in additional cohorts.
authors.affiliation: Department of Pediatrics, Division of Systems Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Chirag J
authors.initials: CJ
authors.lastname: Patel
authors.forename: Mark R
authors.initials: MR
authors.lastname: Cullen
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
authors.forename: Atul J
authors.initials: AJ
authors.lastname: Butte
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002487:Centers for Disease Control and Prevention, U.S.; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D004781:Environmental Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data; D004785:Environmental Pollutants / Q000097:blood / Q000633:toxicity*; D005260:Female; D006801:Humans; D008055:Lipids / Q000097:blood*; D008297:Male; D018977:Micronutrients; D008875:Middle Aged; D009749:Nutrition Surveys; D012737:Sex Factors; D012959:Socioeconomic Factors; D014280:Triglycerides / Q000097:blood; D014481:United States
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004785:Environmental Pollutants; D008055:Lipids; D018977:Micronutrients; D014280:Triglycerides