Soy Intake and Breast Cancer Risk: A Prospective Study of 300,000 Chinese Women and a Dose-Response Meta-Analysis
61 Pages Posted: 12 Jun 2019More...
Background: Epidemiological evidence on the association of soy intake with breast cancer risk is still inconsistent due to different soy intake levels across previous studies and small number of breast cancer cases. We aimed to investigate this issue by analyzing data from the China Kadoorie Biobank (CKB) study and doing a dose-response meta-analysis to integrate existing evidence.
Methods: The CKB study included over 300,000 women aged 30 to 79 from 10 regions across China enrolled between 2004 and 2008, and followed-up for breast cancer events until 31 December 2016. Information on soy intake was collected from baseline, two resurveys and twelve 24-hour dietary recalls. We also searched for relevant prospective cohort studies to do a dose-response meta-analysis.
Findings: The mean soy intake was 9.4 mg/day soy isoflavones among CKB women. During 10 years of follow-up, 2,289 women developed breast cancers. The multivariable-adjusted relative risk was 0.98 (95% confidence interval [CI]: 0.80 to 1.20) for the fourth (19.1 mg/day) versus the first (4.5 mg/day) soy isoflavone intake quartile. Meta-analysis of prospective studies found that each 10 mg/day increment in soy isoflavone intake was associated with a 3% (95%CI: 1% to 5%) reduced risk of breast cancer.
Interpretation: Soy intake at around 20 mg/day of soy isoflavones was not associated with breast cancer risk among Chinese women. Women might need to consume soy at an amount of ï‚³ 35 mg/day soy isoflavones to get benefits (reduced risk by 10%) in preventing breast cancer.
Funding: National Natural Science Foundation of China and National Key Research and Development Program.
Declaration of Interest: All authors declare: no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical Approval: The Ethical Review Committee of the Chinese Center for Disease Control and Prevention (Beijing, China) and the Oxford Tropical Research Ethics Committee, University of Oxford (UK) approved the study.
Keywords: soy intake, breast cancer, prospective cohort study, doseresponse meta-analysis
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