The Who, What, Where, When and Sometimes, Why.

Soy and breast cancer risk

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s 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. 

This topic is under 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.



Komen Perspectives

Read our perspective on soy and breast cancer.*

*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 Therefore, some information may be out of date.    


Study selection criteria: Prospective cohort studies with at least 400 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,
RR (95% CI)

Prospective cohort studies

Fraser et al. [1]

(1,057 cases)

Soy food plus soy milk intake:
High vs. Low

All women:

Premenopausal women:

Postmenopausal women:

Baglia et al. [2]

(1,034 cases)

Soy protein intake in adulthood:
16 or more vs.
4 or fewer g/day

All women:

Premenopausal women:

Postmenopausal women:


Soy protein intake in the teen years:
16 or more vs.
2 or fewer g/day

All women:



Butler et al. [3]

(629 cases)

Soy food intake:
High vs. Low


Travis et al. [4]

(585 cases)

Soy food plus soy milk intake:
More than 20 mg/day vs.
Less than 10 mg/day


Key et al. [5]

(427 cases)

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


Pooled and meta-analyses

Trock et al. [6]


Multiple measures of dietary soy intake:
High vs. Low




Per one gram increase of soy protein intake


Qin et al. [7]

21 studies

Total soy food intake:
High vs. Low




Total tofu intake:
High vs. Low




Total miso intake:
High vs. Low


Chen et al. [8]

17 studies
(women living in Asian countries)

Total soy food intake:
High vs. Low



14 studies
(women living in Western countries)

Total soy food intake:
High vs. Low


Wu et al. [9]

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. [10]

14 studies

Total soy food intake:
High vs. Low


Liu et al. [11]

11 studies
(Chinese women only)

Total soy food intake:
High vs. Low


Wu et al. [12]

10 studies

Total soy food intake:
High vs. Low


Zhao et al. [13]

6 studies

Total soy food intake:
High vs. Low



Study Population
(number of participants)

Soy Supplement Intake
(categories compared)

Relative Risk of Breast Cancer in Women with High versus Low Intake of Soy Supplements,
RR (95% CI) 

Prospective cohort studies

E3N cohort [14]

(3,608 cases)

Current users vs. Non-users




Past users vs. Non-users


VITAL [15]

(880 cases)

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.


  1. Fraser GE, Jaceldo-Siegl K, Orlich M, Mashchak A, Sirirat R, Knutsen S. Dairy, soy, and risk of breast cancer: those confounded milks. Int J Epidemiol. 2020.
  2. Baglia ML, Zheng W, Li H, et al. The association of soy food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status. Int J Cancer. 139(4):742-8, 2016.
  3. Butler LM, Wu AH, Wang R, Koh WP, Yuan JM, Yu MC. A vegetable-fruit-soy dietary pattern protects against breast cancer among postmenopausal Singapore Chinese women. Am J Clin Nutr. 91(4):1013-9, 2010.
  4. Travis RC, Allen NE, Appleby PN, Spencer EA, Roddam AW, Key TJ. A prospective study of vegetarianism and isoflavone intake in relation to breast cancer risk in British women. Int J Cancer.122(3):705-10, 2008.
  5. Key TJ, Appleby PN, Beral V, et al. Soya foods and breast cancer risk: a prospective study in Hiroshima and Nagasaki, Japan. Br J Cancer. 81(7):1248-1256, 1999.
  6. Trock BJ, Hilakivi-Clarke L, Clarke R. Meta-analysis of soy intake and breast cancer risk. J Natl Cancer Inst. 98(7):459-71, 2006.
  7. Qin LQ, Xu JY, Wany PY, Hoshi K. Soyfood intake in the prevention of breast cancer risk in women: a meta-analysis of observational epidemiological studies. J Nutr Sci Vitaminol (Tokyo). 52(6):428-36, 2006.
  8. Chen M, Rao Y, Zheng Y, et al. Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: a meta-analysis of epidemiological studies. PLoS One. 9(2):e89288, 2014.
  9. Wu AH, Yu MC, Tseng CC, Pike MC. Epidemiology of soy exposures and breast cancer risk. Br J Cancer. 98(1):9-14, 2008.
  10. Dong JY, Qin LQ. Soy isoflavones consumption and risk of breast cancer incidence or recurrence: a meta-analysis of prospective studies. Breast Cancer Res Treat. 125(2):315-23, 2011.
  11. Liu XO, Huang YB, Gao Y, et al. Association between dietary factors and breast cancer risk among Chinese females: systematic review and meta-analysis. Asian Pac J Cancer Prev. 15(3):1291-8, 2014.
  12. Wu J, Zeng R, Huang J, et al. Dietary protein sources and incidence of breast cancer: a dose-response meta-analysis of prospective studies. Nutrients. 8(11): 730, 2016.
  13. Zhao TT, Jin F, Li JG, et al. Dietary isoflavones or isoflavone-rich food intake and breast cancer risk: A meta-analysis of prospective cohort studies. Clin Nutr. 38(1):136-145, 2019.
  14. Touillaud M, Gelot A, Mesrine S, et al. Use of dietary supplements containing soy isoflavones and breast cancer risk among women aged >50 y: a prospective study. Am J Clin Nutr. 109(3):597-605, 2019.
  15. Brasky TM, Lampe JW, Potter JD, Patterson RE, White E. Specialty supplements and breast cancer risk in the VITamins And Lifestyle (VITAL) Cohort. Cancer Epidemiol Biomarkers Prev. 19(7):1696-708, 2010.


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