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Folate intake and the risk of breast cancer: a dose-response meta-analysis of prospective studies.

Abstract

BACKGROUND

Previous observational studies regarding the existence of an association between folate intake and the risk of breast cancer have been inconsistent. This study aimed to summarize the evidence regarding this relationship using a dose-response meta-analytic approach.

METHODOLOGY AND PRINCIPAL FINDINGS

We performed electronic searches of the PubMed, EmBase, and Cochrane Library databases to identify studies published through June 2013. Only prospective observational studies that reported breast cancer effect estimates with 95% confidence intervals (CIs) for more than 2 folate intake categories were included. We excluded traditional case-control studies because of possible bias from various confounding factors. Overall, we included 14 prospective studies that reported data on 677,858 individuals. Folate intake had little effect on the breast cancer risk (relative risk (RR) for highest versus lowest category = 0.97; 95% CI, 0.90-1.05; P = 0.451). Dose-response meta-analysis also suggested that a 100 µg/day increase in folate intake had no significant effect on the risk of breast cancer (RR = 0.99; 95% CI, 0.98-1.01; P = 0.361). Furthermore, we used restricted cubic splines to evaluate the nonlinear relationship between folate intake and the risk of breast cancer, and discovered a potential J-shaped correlation between folate intake and breast cancer risk (P = 0.007) and revealed that a daily folate intake of 200-320 µg was associated with a lower breast cancer risk; however, the breast cancer risk increased significantly with a daily folate intake >400 µg.

CONCLUSION/SIGNIFICANCE

Our study revealed that folate intake had little or no effect on the risk of breast cancer; moreover, a dose-response meta-analysis suggested a J-shaped association between folate intake and breast cancer.

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  • Authors+Show Affiliations

    ,

    Department of Oncology, Shanghai Seventh People's Hospital, Shanghai, China.

    ,

    Medical Research Center, Taizhou Hospital of Zhejiang Province, Wenzhou Medical College, Linhai, Zhejiang, China.

    ,

    Department of Oncology, Shanghai Seventh People's Hospital, Shanghai, China.

    ,

    Department of Oncology, Shanghai Seventh People's Hospital, Shanghai, China.

    ,

    Department of Oncology, Shanghai Seventh People's Hospital, Shanghai, China.

    Department of Rehabilitation Institute, Shanghai Seventh People's Hospital, Shanghai, China.

    Source

    PloS one 9:6 2014 pg e100044

    MeSH

    Breast Neoplasms
    Dose-Response Relationship, Drug
    Female
    Folic Acid
    Humans
    Observational Studies as Topic
    Prospective Studies
    Risk Factors
    Vitamin B Complex

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    24932496

    Citation

    Zhang, Yu-Fei, et al. "Folate Intake and the Risk of Breast Cancer: a Dose-response Meta-analysis of Prospective Studies." PloS One, vol. 9, no. 6, 2014, pp. e100044.
    Zhang YF, Shi WW, Gao HF, et al. Folate intake and the risk of breast cancer: a dose-response meta-analysis of prospective studies. PLoS ONE. 2014;9(6):e100044.
    Zhang, Y. F., Shi, W. W., Gao, H. F., Zhou, L., Hou, A. J., & Zhou, Y. H. (2014). Folate intake and the risk of breast cancer: a dose-response meta-analysis of prospective studies. PloS One, 9(6), pp. e100044. doi:10.1371/journal.pone.0100044.
    Zhang YF, et al. Folate Intake and the Risk of Breast Cancer: a Dose-response Meta-analysis of Prospective Studies. PLoS ONE. 2014;9(6):e100044. PubMed PMID: 24932496.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Folate intake and the risk of breast cancer: a dose-response meta-analysis of prospective studies. AU - Zhang,Yu-Fei, AU - Shi,Wei-Wu, AU - Gao,Hong-Fang, AU - Zhou,Li, AU - Hou,An-Ji, AU - Zhou,Yu-Hao, Y1 - 2014/06/16/ PY - 2013/10/10/received PY - 2014/05/22/accepted PY - 2014/6/17/entrez PY - 2014/6/17/pubmed PY - 2015/10/21/medline SP - e100044 EP - e100044 JF - PloS one JO - PLoS ONE VL - 9 IS - 6 N2 - BACKGROUND: Previous observational studies regarding the existence of an association between folate intake and the risk of breast cancer have been inconsistent. This study aimed to summarize the evidence regarding this relationship using a dose-response meta-analytic approach. METHODOLOGY AND PRINCIPAL FINDINGS: We performed electronic searches of the PubMed, EmBase, and Cochrane Library databases to identify studies published through June 2013. Only prospective observational studies that reported breast cancer effect estimates with 95% confidence intervals (CIs) for more than 2 folate intake categories were included. We excluded traditional case-control studies because of possible bias from various confounding factors. Overall, we included 14 prospective studies that reported data on 677,858 individuals. Folate intake had little effect on the breast cancer risk (relative risk (RR) for highest versus lowest category = 0.97; 95% CI, 0.90-1.05; P = 0.451). Dose-response meta-analysis also suggested that a 100 µg/day increase in folate intake had no significant effect on the risk of breast cancer (RR = 0.99; 95% CI, 0.98-1.01; P = 0.361). Furthermore, we used restricted cubic splines to evaluate the nonlinear relationship between folate intake and the risk of breast cancer, and discovered a potential J-shaped correlation between folate intake and breast cancer risk (P = 0.007) and revealed that a daily folate intake of 200-320 µg was associated with a lower breast cancer risk; however, the breast cancer risk increased significantly with a daily folate intake >400 µg. CONCLUSION/SIGNIFICANCE: Our study revealed that folate intake had little or no effect on the risk of breast cancer; moreover, a dose-response meta-analysis suggested a J-shaped association between folate intake and breast cancer. SN - 1932-6203 UR - https://www.unboundmedicine.com/medline/citation/24932496/Folate_intake_and_the_risk_of_breast_cancer:_a_dose_response_meta_analysis_of_prospective_studies_ L2 - http://dx.plos.org/10.1371/journal.pone.0100044 DB - PRIME DP - Unbound Medicine ER -