The Volume of Nipple Aspirate Fluid Is Not Affected by 6 Months of Treatment with Soy Foods in Premenopausal Women1–4

Abstract

Based on the hypothesis that soy food consumption may influence breast tissue activity, we examined its effect on the production of nipple aspirate fluid (NAF), a possible indicator of breast cancer risk. Of 310 premenopausal women screened, 112 (36%) produced at least 10 μL of NAF, the minimum for study participation. In a crossover design, we randomized 96 women to 2 groups who, in reverse order, consumed a high-soy diet with 2 soy servings/d (1 serving = 177 mL soy milk, 126 g tofu, or 23 g soy nuts) and a low-soy diet with <3 servings/wk of soy for 6 mo each separated by a 1-mo washout period. During each diet period, 3 NAF samples were obtained (baseline and 3 and 6 mo) using a FirstCyte Aspirator and 4 urine samples (baseline and 1, 3, and 6 mo) were analyzed for isoflavonoids by liquid chromatography tandem MS. Adherence to the study protocol according to 24-h dietary recalls and urinary isoflavonoid excretion was high. The drop-out rate was 15% (n = 14); 82 women completed the intervention. The 2 groups produced similar mean NAF volumes at baseline (P = 0.95) but differed in age and previous soy intake and in their response to the intervention (P = 0.03). In both groups, NAF volume decreased during the first 3 mo of the high-soy diet period and returned to baseline at 6 mo, but there was no effect of the high-soy diet on NAF volume (P = 0.50 for diet; P-interaction = 0.21 for diet with time). Contrary to an earlier report, soy foods in amounts consumed by Asians did not increase breast tissue activity as assessed by NAF volume.

Soy Food Intake and Biomarkers of Breast Cancer Risk: Possible Difference in Asian Women?

“…The second trial (BEAN2) was a 13-month randomized, crossover study consisting of a 6-month intervention and a 6-month control phase, separated by a 1-month washout period (7). The exclusion criteria were the same as in BEAN1 except for the mammogram requirement.…”

“…Using existing data from two dietary intervention studies conducted among premenopausal women in Hawaii (6, 7), we compared the effects of two daily servings of soy foods on several biomarkers of breast cancer risk by ethnic background, i.e., Asian vs non-Asian (Caucasian, Native Hawaiian, and other). The measured outcomes included sex steroids in serum, NAF, and urine, i.e., estrone (E 1 ), estradiol (E 2 ), estrone sulfate (E 1 S), sex hormone-binding globulin (SHBG), progesterone, C-reactive protein (CRP), interleukin-6 (IL-6), adiponectin, and leptin as markers of inflammation, NAF volume, mammographic density, and urinary isoflavones.…”

Oestrogen levels in serum and urine of premenopausal women eating low and high amounts of meat

“…The BEAN2 trial was conducted in 2007–2010 as a cross-over study with 6 months on a high and a low soy diet each separated by a 1-month washout period (21) . Of the 96 randomized women, 82 participants completed both diet periods.…”

“…Using validated radioimmunoassays, 5 repeated serum samples for BEAN1 and 3 samples for BEAN2 were analyzed for E 1 and E 2 in 0.5 mL serum (24) . Based on blinded samples, the interassay coefficients of variations (CV) were 17.7% for E 1 and 11.2% for E 2 in BEAN1 and 15.0% for both E 1 and E 2 in BEAN2 (17,21) .…”

“…Urinary creatinine concentrations were measured using a Roche-Cobas MiraPlus clinical chemistry autoanalyzer (Roche Diagnostics, Switzerland). Urinary isoflavonoids as a biomarker for soy intake were assessed by high-pressure liquid chromatography in BEAN1 (17) and by LCMS in BEAN2 (21) . All urinary measurements were expressed per mg creatinine to adjust for urine volume.…”