This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: The potential benefit of soy on breast cancer risk remains unclear.
Findings from some case-control studies have suggested soy products may lower the risk of breast cancer.
However, findings from large prospective cohort studies have been mixed. The topic is under active study.
Learn more about soy and breast cancer risk.
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Read our perspective on soy and breast cancer (May 2015).*
Learn More | Current Article
Read our perspective on soy and the risk breast cancer(February 2010).*
*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Study selection criteria: Prospective cohort studies with at least 400 breast cancer cases, case-control studies with at least 1,000 breast cancer cases, meta-analyses and pooled analyses.
Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Dietary Soy Intake(categories compared)
Relative Risk of Breast Cancer in Women with High versus Low Dietary Intake of Soy Products,RR (95% CI)
Prospective cohort studies
Baglia et al. 
Soy protein intake in adulthood: 16 or more vs. 4 or fewer g/day
Soy protein intake in the teen years: 16 or more vs. 2 or fewer g/day
All women: 0.95 (0.77-1.16) Premenopausal: 0.69 (0.45-1.04) Postmenopausal: 1.06 (0.84-1.34)
Butler et al. 
Soy food intake:High vs. Low
Travis et al. 
Soy food plus soy milk intake:More than 20 mg/day vs. Less than 10 mg/day
Key et al. 
Tofu intake:5 or more vs.1 or fewer times/week
Miso soup intake:5 or more times/week vs. Never
Total intake of miso soup and tofu: High vs. Low
Zaineddin et al. 
Tofu intake: High vs. None
Soy milk intake: High vs. None
Sanderson et al. 
Soy food intake:More than12 vs.Less than 7 grams/day
Horn-Ross et al. 
Soy milk intake:Any vs. None
Miso soup intake:1 or more serving/month vs.None
Hirose et al. 
Miso soup intake:Daily vs.Less than daily
Tofu intake:3 or more times/week vs.3 or fewer times/month
Pooled and meta-analyses
Trock et al. 
Multiple measures of dietary soy intake:High vs. Low
Per one gram increase of soy protein intake
Qin et al. 
Total soy food intake:High vs. Low
Total tofu intake:High vs. Low
Total miso intake:High vs. Low
Chen et al. 
17 studies (women living in Asian countries)
14 studies (women living in Western countries)
Wu et al. 
8 studies(Asian and Asian American women only)
Total soy food intake:20 or more vs. 5 or fewer mg/day
Total soy food intake:10-20 vs. 5 or fewer mg/day
11 studies(Western women only)
Total soy food intake:6 or more vs. Less than 1 mg/week
Dong et al. 
Liu et al. 
11 studies(Chinese women only)
Soy Supplement Intake (categories compared)
Relative Risk of Breast Cancer in Women with High versus Low Intake of Soy Supplements, RR (95% CI)
Users vs. Non-users
† All women in the study were premenopausal. ‡ Authors cautioned interpreting a protective effect due to potential problems with measures of soy intake and lack of a dose-response relationship between soy and breast cancer risk.
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