Abstract
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 conducting a dose–response meta-analysis to integrate existing evidence. The CKB study included over 300,000 women aged 30–79 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-h dietary recalls. We also searched for relevant prospective cohort studies to do a dose–response meta-analysis. The mean (SD) soy intake was 9.4 (5.4) mg/day soy isoflavones among CKB women. During 10 years of follow-up, 2289 women developed breast cancers. The multivariable-adjusted relative risk was 1.00 (95% confidence interval [CI] 0.81–1.22) 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 1–5%) reduced risk of breast cancer. The CKB study demonstrated that moderate soy intake was not associated with breast cancer risk among Chinese women. Higher amount of soy intake might provide reasonable benefits for the prevention of breast cancer.
Highlights
Breast cancer is the most common cancer and one of the leading causes of cancer death among women throughout the world [1]
Soy foods are major sources of dietary isoflavones, which share structural similarities with 17-β-estradiol and may serve as functional estrogen antagonists to protect against breast cancer [6, 7]
Using the data from the China Kadoorie Biobank (CKB), a large scale prospective cohort study involving over 300,000 women from 10 geographically and economically diverse regions in China, we evaluated the relationship between soy intake and risk of incident breast cancer
Summary
Breast cancer is the most common cancer and one of the leading causes of cancer death among women throughout the world [1]. Several meta-analyses concluded that higher amount of soy intake was associated with lower risk of incident breast cancer among Asian women but not among their Western counterparts [9,10,11,12]. As most previous cohort studies in Asia have limited numbers of breast cancer cases, insufficient statistical power as well as different cut-off values for soy intake categories may explain this inconsistency. Using the data from the China Kadoorie Biobank (CKB), a large scale prospective cohort study involving over 300,000 women from 10 geographically and economically diverse regions in China, we evaluated the relationship between soy intake and risk of incident breast cancer. In order to provide a clearer picture on the soy-breast cancer relationship, we did a dose–response meta-analysis to integrate results of prospective cohort studies
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