The Association Between Phytosterol Intake and Breast Cancer Incidence in the Adventist Health Study-2 Cohort

Breast cancer is the most diagnosed form of cancer among American women. Worldwide, it is second only to lung cancer. Phytosterols are phytochemicals found in plant foods that have potential benefits for breast cancer. Research on phytosterols and cancer associations to date has been limited to breast cancer cell lines and animal studies, and the results have been promising. Our objective is to examine the association between breast cancer incidence and phytosterol intake in the Adventist Health Study-2, a large cohort in North America. The present study estimated the association between phytosterol intake and breast cancer incidence in 52,734 females who were part of the Adventist Health Study 2 (AHS-2) cohort. Breast cancer cases (n = 1050) were ascertained with tumor registries from 2008 to 2014. Phytosterols content in foods was quantified by using USDA 17 and other published sources. These values were used to estimate phytosterol intake from food intake assessed by a self-administered food frequency questionnaires (FFQ). Hazard ratios were below the null, but statistically non-significant for β-sitosterol [HR = 0.77, 95%CI (0.44–1.36)], campesterol [HR = 0.84, 95%CI (0.46–1.55)], stigmasterol [HR = 0.76 (0.46–1.26)], and total phytosterol [HR = 0.77, 95%CI (0.43–1.40)]. In premenopausal women, HRs ranged between 0.95–1.72; in postmenopausal women, HRs were below the null, ranging between 0.67–0.83. In both premenopausal and postmenopausal women, HRs were statistically non-significant. The inverse association between phytosterol consumption and breast cancer incidence appears uncertain. The uncertainty possibly could be due to lack of power or measurement error. Additional epidemiological studies with a larger number of breast cancer cases, improved phytosterol intake estimates, or both are needed. Unilever Research &Development, Vlaardingen, The Netherlands.