title: Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis.
abstract: BACKGROUND
  Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.
  
  
  METHODS
  We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.
  
  
  RESULTS
  In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case-control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case-control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case-control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.
  
  
  CONCLUSIONS
  Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.
authors.affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: P
authors.initials: P
authors.lastname: Chen
authors.affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: R
authors.initials: R
authors.lastname: Chu
authors.affiliation: 1] Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of the Chinese Academy of Sciences, Shanghai 200031, People's Republic of China [2] Key Laboratory of Food Safety Risk Assessment, Ministry of Health, Beijing 100021, People's Republic of China [3] School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, People's Republic of China.
authors.forename: H
authors.initials: H
authors.lastname: Wang
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D014803:Vitamin B Complex / Q000008:administration & dosage*
chemical_list: D014803:Vitamin B Complex; D005492:Folic Acid