Research table: 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: A potential link between soy and a decreased breast cancer risk is under study.

Findings from some case-control studies have suggested soy products may be linked to a lower 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 soy and breast cancer survival.

Learn about the strengths and weaknesses of different types of studies.

See how this risk factor compares with other risk factors for 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 Therefore, some information may be out of date.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	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
China Kadoorie Biobank Collaborative Group [1]	300,852 (2,289 cases)	Soy food plus soy milk intake: 4 or more times/week vs. Never or rarely	0.98 (0.80-1.20)†
UK Women’s Cohort Study [2]	32,228 (1,822 cases)	Soy product intake: High vs. Low	0.97 (0.90-1.05)†
Fraser et al. [3]	52,795 (1,057 cases)	Soy food plus soy milk intake: High vs. Low	0.93 (0.75-1.14)†
Baglia et al. [4]	70,578 (1,034 cases)	Soy protein intake in adulthood: 16 or more vs. 4 or fewer g/day	All women: 0.78 (0.63-0.97) Premenopausal women: 0.46 (0.29-0.74) Postmenopausal women: 0.90 (0.71-1.16)
		Soy protein intake in the teen years: 16 or more vs. 2 or fewer g/day	0.95 (0.77-1.16)†
Japan Public Health Center-based Prospective Study [5]	47,614 (825 cases)	Soy food plus soy milk intake: High vs. Low	1.07 (0.79-1.46)
Butler et al. [6]	34,028 (629 cases)	Soy food intake: High vs. Low	0.83 (0.62-1.11)
Travis et al. [7]	37,643 (585 cases)	Soy food plus soy milk intake: More than 20 mg/day vs. Less than 10 mg/day	1.17 (0.79-1.71)
Key et al. [8]	34,759 (427 cases)	Tofu intake: 5 or more vs. 1 or fewer times/week	1.07 (0.78-1.47)
		Miso soup intake: 5 or more times/week vs. Never	0.87 (0.68-1.120)
		Total intake of miso soup and tofu: High vs. Low	0.94 (0.73-1.20)
Pooled and meta-analyses
Trock et al. [9]	981,379	Multiple measures of dietary soy intake: High vs. Low	0.86 (0.75-0.99)‡
		Per one gram increase of soy protein intake	0.97 (0.94-1.00)‡
Chen et al. [10]	17 studies (women living in Asian countries)	Total soy food intake: High vs. Low	0.59 (0.48-0.69)
	14 studies (women living in Western countries)	Total soy food intake: High vs. Low	0.90 (0.77-1.04)
Wu et al. [11]	8 studies (Asian and Asian American women only)	Total soy food intake: 20 or more vs. 5 or fewer mg/day	0.71 (0.60-0.85)
		Total soy food intake: 10-20 vs. 5 or fewer mg/day	0.88 (0.78-0.98)
	11 studies (Western women only)	Total soy food intake: 6 or more vs. Less than 1 mg/week	1.04 (0.97-1.11)
Shin et al. [12]	8 studies (Asian women only)	Total soy food intake: High vs. Low	0.90 (0.67-1.20)
Dong et al. [13]	14 studies	Total soy food intake: High vs. Low	0.89 (0.79-0.99)
Liu et al. [14]	11 studies (Chinese women only)	Total soy food intake: High vs. Low	0.65 (0.43-0.99)
Wu et al. [15]	10 studies	Total soy food intake: High vs. Low	0.92 (0.84-1.00)
Zhao et al. [16]	6 studies	Total soy food intake: High vs. Low	0.87 (0.76-1.00)
Study	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 [17]	76,442 (3,608 cases)	Current users vs. Non-users	0.92 (0.76-1.11)
		Past users vs. Non-users	1.01 (0.88-1.16)
VITAL [18]	35,016 (880 cases)	Users vs. Non-users	1.04 (0.74-1.48)

† When the data for premenopausal women and postmenopausal women were examined separately, results were similar (not statistically significant). 
 
‡ Authors cautioned interpreting a protective effect due to potential problems with measures of soy intake and a lack of a dose-response relationship between soy and breast cancer risk.

References

1. Wei Y, Jun Lv J, Guo Y, et al. for the China Kadoorie Biobank Collaborative Group. Soy intake and breast cancer risk: a prospective study of 300,000 Chinese women and a dose-response meta-analysis. Eur J Epidemiol. 35(6):567-578, 2020.
2. Dunneram Y, Greenwood DC, Cade JE. Diet and risk of breast, endometrial and ovarian cancer: UK Women’s Cohort Study. Br J Nutr. 122(5):564-574, 2019.
3. 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.
4. 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.
5. Shirabe R, Saito E, Sawada N, et al. for the JPHC Study Group. Fermented and nonfermented soy foods and the risk of breast cancer in a Japanese population-based cohort study. Cancer Med. 10(2):757-771, 2021.
6. 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.
7. 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.
8. 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.
9. 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.
10. 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.
11. Wu AH, Yu MC, Tseng CC, Pike MC. Epidemiology of soy exposures and breast cancer risk. Br J Cancer. 98(1):9-14, 2008.
12. Shin S, Fu J, Shin WK, Huang D, Min S, Kang D. Association of food groups and dietary pattern with breast cancer risk: A systematic review and meta-analysis. Clin Nutr. 42(3):282-297, 2023.
13. 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.
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.

Updated 11/08/23