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Dairy, soy, and risk of breast cancer: those confounded milks.
Int J Epidemiol. 2020 Oct 01; 49(5):1526-1537.IJ

Abstract

BACKGROUND

Associations between soy, dairy intakes and breast cancer risk are inconsistent. No studies exist with large numbers of dairy consumers and soy consumers to assess mutual confounding.

METHODS

The study cohort contains 52 795 North American women, initially free of cancer, followed for 7.9 years (29.7% were Black). Dietary intakes were estimated from food frequency questionnaires and, for 1011 calibration study subjects, from six structured 24-h dietary recalls. Incident invasive breast cancers were detected mainly by matching with cancer registries. Analyses used multivariable proportional hazards regression.

RESULTS

The participants (mean age of 57.1 years) experienced 1057 new breast cancer cases during follow-up. No clear associations were found between soy products and breast cancer, independently of dairy. However, higher intakes of dairy calories and dairy milk were associated with hazard ratios (HRs) of 1.22 [95% confidence interval (CI): 1.05-1.40] and 1.50 (95% CI 1.22-1.84), respectively, comparing 90th to 10th percentiles of intakes. Full fat and reduced fat milks produced similar results. No important associations were noted with cheese and yogurt. Substituting median intakes of dairy milk users by those of soy milk consumers was associated with HR of 0.68 (95% CI: 0.55-0.85). Similar-sized associations were found among pre- and post-menopausal cases, with CIs also excluding the null in estrogen receptor (ER+, ER-), and progesterone receptor (PR+) cancers. Less biased calibrated measurement-error adjusted regressions demonstrated yet stronger, but less precise, HRs and CIs that still excluded the null.

CONCLUSIONS

Higher intakes of dairy milk were associated with greater risk of breast cancer, when adjusted for soy intake. Current guidelines for dairy milk consumption could be viewed with some caution.

Links

Authors+Show Affiliations

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

Jaceldo-Siegl K

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

Center for Nutrition, Healthy Lifestyle, and Disease Prevention, School of Public Health, Loma Linda University, Loma Linda, CA, USA.

MeSH

AnimalsBreast NeoplasmsDairy ProductsDietFemaleHumansMiddle AgedMilkReceptors, EstrogenRisk FactorsSoy FoodsYogurt

Pub Type(s)

Journal Article

Research Support, N.I.H., Extramural

Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

32095830

Citation

Fraser, Gary E., et al. "Dairy, Soy, and Risk of Breast Cancer: Those Confounded Milks." International Journal of Epidemiology, vol. 49, no. 5, 2020, pp. 1526-1537.

Fraser GE, Jaceldo-Siegl K, Orlich M, et al. Dairy, soy, and risk of breast cancer: those confounded milks. Int J Epidemiol. 2020;49(5):1526-1537.

Fraser, G. E., Jaceldo-Siegl, K., Orlich, M., Mashchak, A., Sirirat, R., & Knutsen, S. (2020). Dairy, soy, and risk of breast cancer: those confounded milks. International Journal of Epidemiology, 49(5), 1526-1537. https://doi.org/10.1093/ije/dyaa007

Fraser GE, et al. Dairy, Soy, and Risk of Breast Cancer: Those Confounded Milks. Int J Epidemiol. 2020 Oct 1;49(5):1526-1537. PubMed PMID: 32095830.

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - Dairy, soy, and risk of breast cancer: those confounded milks. AU - Fraser,Gary E, AU - Jaceldo-Siegl,Karen, AU - Orlich,Michael, AU - Mashchak,Andrew, AU - Sirirat,Rawiwan, AU - Knutsen,Synnove, PY - 2019/12/13/received PY - 2020/1/21/accepted PY - 2020/2/26/pubmed PY - 2021/4/28/medline PY - 2020/2/26/entrez PY - 2020/2/25/pmc-release KW - Soy isoflavones KW - Western population KW - breast cancer KW - meat analogues KW - soy intake KW - soy milk KW - tofu SP - 1526 EP - 1537 JF - International journal of epidemiology JO - Int J Epidemiol VL - 49 IS - 5 N2 - BACKGROUND: Associations between soy, dairy intakes and breast cancer risk are inconsistent. No studies exist with large numbers of dairy consumers and soy consumers to assess mutual confounding. METHODS: The study cohort contains 52 795 North American women, initially free of cancer, followed for 7.9 years (29.7% were Black). Dietary intakes were estimated from food frequency questionnaires and, for 1011 calibration study subjects, from six structured 24-h dietary recalls. Incident invasive breast cancers were detected mainly by matching with cancer registries. Analyses used multivariable proportional hazards regression. RESULTS: The participants (mean age of 57.1 years) experienced 1057 new breast cancer cases during follow-up. No clear associations were found between soy products and breast cancer, independently of dairy. However, higher intakes of dairy calories and dairy milk were associated with hazard ratios (HRs) of 1.22 [95% confidence interval (CI): 1.05-1.40] and 1.50 (95% CI 1.22-1.84), respectively, comparing 90th to 10th percentiles of intakes. Full fat and reduced fat milks produced similar results. No important associations were noted with cheese and yogurt. Substituting median intakes of dairy milk users by those of soy milk consumers was associated with HR of 0.68 (95% CI: 0.55-0.85). Similar-sized associations were found among pre- and post-menopausal cases, with CIs also excluding the null in estrogen receptor (ER+, ER-), and progesterone receptor (PR+) cancers. Less biased calibrated measurement-error adjusted regressions demonstrated yet stronger, but less precise, HRs and CIs that still excluded the null. CONCLUSIONS: Higher intakes of dairy milk were associated with greater risk of breast cancer, when adjusted for soy intake. Current guidelines for dairy milk consumption could be viewed with some caution. SN - 1464-3685 UR - https://www.unboundmedicine.com/medline/citation/32095830/full_citation DB - PRIME DP - Unbound Medicine ER -