title: Dairy food intake in relation to semen quality and reproductive hormone levels among physically active young men.
abstract: OBJECTIVE
  Is increased consumption of dairy foods associated with lower semen quality?
  
  
  CONCLUSIONS
  We found that intake of full-fat dairy was inversely related to sperm motility and morphology. These associations were driven primarily by intake of cheese and were independent of overall dietary patterns.
  
  
  BACKGROUND
  It has been suggested that environmental estrogens could be responsible for the putative secular decline in sperm counts. Dairy foods contain large amounts of estrogens. While some studies have suggested dairy as a possible contributing factor for decreased semen quality, this finding has not been consistent across studies.
  
  
  METHODS
  The Rochester Young Men's Study (n = 189) was a cross-sectional study conducted between 2009 and 2010 at the University of Rochester.
  
  
  METHODS
  Men aged 18-22 years were included in this analysis. Diet was assessed via food frequency questionnaire. Linear regression was used to analyze the relation between dairy intake and conventional semen quality parameters (total sperm count, sperm concentration, progressive motility, morphology and ejaculate volume) adjusting for age, abstinence time, race, smoking status, body mass index, recruitment period, moderate-to-intense exercise, TV watching and total calorie intake.
  
  
  RESULTS
  Total dairy food intake was inversely related to sperm morphology (P-trend = 0.004). This association was mostly driven by intake of full-fat dairy foods. The adjusted difference (95% confidence interval) in normal sperm morphology percent was -3.2% (-4.5 to -1.8) between men in the upper half and those in the lower half of full-fat dairy intake (P < 0.0001), while the equivalent contrast for low-fat dairy intake was less pronounced [-1.3% (-2.7 to -0.07; P= 0.06)]. Full-fat dairy intake was also associated with significantly lower percent progressively motile sperm (P= 0.05).
  
  
  CONCLUSIONS
  As it was a cross-sectional study, causal inference is limited.
  
  
  CONCLUSIONS
  Further research is needed to prove a causal link between a high consumption of full-fat dairy foods and detrimental effects on semen quality. If verified our findings would mean that intake of full-fat dairy foods should be considered in attempts to explain secular trends in semen quality and that men trying to have children should restrict their intake.
  
  
  BACKGROUND
  European Union Seventh Framework Program (Environment), 'Developmental Effects of Environment on Reproductive Health' (DEER) grant 212844. Grant P30 DK046200 and Ruth L. Kirschstein National Research Service Award T32 DK007703-16 from the National Institutes of Health. None of the authors has any conflicts of interest to declare.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA. mafeiche@hsph.harvard.edu
authors.forename: M
authors.initials: M
authors.lastname: Afeiche
authors.forename: P L
authors.initials: PL
authors.lastname: Williams
authors.forename: J
authors.initials: J
authors.lastname: Mendiola
authors.forename: A J
authors.initials: AJ
authors.lastname: Gaskins
authors.forename: N
authors.initials: N
authors.lastname: Jørgensen
authors.forename: S H
authors.initials: SH
authors.lastname: Swan
authors.forename: J E
authors.initials: JE
authors.lastname: Chavarro
mesh_terms: D000293:Adolescent; D000328:Adult; D002611:Cheese; D003430:Cross-Sectional Studies; D003611:Dairy Products; D004032:Diet; D006801:Humans; D008297:Male; D055101:Semen Analysis; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*
keywords: dairy; diet; environmental effects; semen quality