title: Prospective studies of dairy product and calcium intakes and prostate cancer risk: a meta-analysis.
abstract: BACKGROUND
  The Dietary Guidelines for Americans 2005 recommends that Americans increase their intake of dairy products. However, some studies have reported that increasing dairy product intake is associated with an increased risk of prostate cancer. We conducted a meta-analysis to examine associations between intakes of calcium and dairy products and the risk of prostate cancer.
  
  
  METHODS
  We searched Medline for prospective studies published in English-language journals from 1966 through May 2005. We identified 12 publications that used total, advanced, or fatal prostate cancer as end points and reported associations as relative risks (RRs) with 95% confidence intervals (CIs) by category of dairy product or calcium intake. Data were extracted using standardized data forms. Random-effects models were used to pool study results and to assess dose-response relationships between dairy product or calcium intakes and the risk of prostate cancer. We conducted sensitivity analyses by changing criteria for inclusion of studies or by using fixed-effects models. All statistical tests were two-sided.
  
  
  RESULTS
  Men with the highest intake of dairy products (RR =1.11 [95% CI = 1.00 to 1.22], P = .047) and calcium (RR = 1.39 [95% CI = 1.09 to 1.77], P = .018) were more likely to develop prostate cancer than men with the lowest intake. Dose-response analyses suggested that dairy product and calcium intakes were each positively associated with the risk of prostate cancer (Ptrend = .029 and .014, respectively). Sensitivity analyses generally supported these associations, although the statistical significance was attenuated. The pooled relative risks of advanced prostate cancer were 1.33 (95% CI = 1.00 to 1.78; P = .055) for the highest versus lowest intake categories of dairy products and 1.46 (95% CI = 0.65 to 3.25; P > .2) for the highest versus lowest intake categories of calcium.
  
  
  CONCLUSIONS
  High intake of dairy products and calcium may be associated with an increased risk of prostate cancer, although the increase appears to be small.
authors.affiliation: Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Michael P
authors.initials: MP
authors.lastname: LaValley
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Tucker
mesh_terms: D002136:Calcium, Dietary / Q000008:administration & dosage* / Q000009:adverse effects*; D016022:Case-Control Studies; D016001:Confidence Intervals; D003611:Dairy Products / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008297:Male; D011939:Mental Recall; D016017:Odds Ratio; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000139:chemically induced / Q000453:epidemiology* / Q000209:etiology* / Q000517:prevention & control; D018570:Risk Assessment; D012307:Risk Factors; D015983:Selection Bias; D014481:United States / Q000453:epidemiology
chemical_list: D002136:Calcium, Dietary