Effects of a 2-Year Randomized Soy Intervention on Sex Hormone Levels in Premenopausal Women

The association of urinary estrogen levels with urinary isoflavone levels: Difference between premenopausal women and postmenopausal women

Results of studies on the associations of soy food intake with urinary estrogen levels in premenopausal women and in postmenopausal women have been inconsistent. We examined the associations of urinary isoflavone levels as well as soy food intake with estrone (E1) and estradiol (E2) in pre- and postmenopausal women. In addition, we compared the levels of isoflavones, E1 and E2 across current hormone users such as those receiving hormone replacement therapy and those using oral contraceptives and non-users among both pre- and postmenopausal women. Urinary levels of isoflavones, E1 and E2 in 498 women (36 hormone users and 462 non-users) were analyzed. Premenopausal women with a higher frequency of soy food intake had higher urinary isoflavone levels, but there were no significant associations between E1 and E2 levels and urinary isoflavone levels. Levels of E1 and E2 in hormone users were significantly lower than those in hormone non-users among premenopausal women, but levels of E1 and E2 in hormone users were significantly higher than those in hormone non-users among postmenopausal women. Postmenopausal women with a higher frequency of soy food intake had higher urinary isoflavone levels, and postmenopausal women with high urinary isoflavone levels had significantly higher E1 and E2 levels. In conclusion, the associations of urinary isoflavone levels with urinary estrogen levels differed with menopausal status. Urinary levels of E1 and E2 were high in postmenopausal women with high urinary isoflavone levels but not in premenopausal women with high urinary isoflavone levels.

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

Soy foods may protect against breast cancer in Asian but not in Western populations. We examined if the levels of various markers of breast cancer risk and inflammation, as well as the effects of soy food consumption on these markers, differ between Asian and non-Asian premenopausal women in two soy intervention trials. One study randomized 220 women to a 2-yr intervention and the other one randomized 96 women in a crossover design to examine the effects of consumption of 2 daily soy servings on nipple aspirate fluid (NAF) volume; estrogens in serum, NAF, and urine; insulin-like growth factor-1 (IGF-1), IGF-binding protein 3, and inflammatory markers in serum; and mammographic densities. Mixed linear models were applied to assess ethnic differences in biomarkers and response to the soy diet. Serum C-reactive protein, serum leptin, NAF volume, and NAF estrone sulfate were lower, while urinary isoflavones were higher in Asian than in non-Asian women. A significant interaction (p_interaction = 0.05) between ethnicity and soy diet was observed for IGF-1 but not for other biomarkers. The current findings suggest possible ethnic differences in levels of biomarkers for breast cancer risk but little evidence that Asian women respond differently to soy foods than non-Asian women.

Effects of soy on the mammary glands of premenopausal female monkeys

OBJECTIVE

To evaluate the interactive effects of dietary soy and menstrual cycle phase on breast proliferation, apoptosis, and sex steroid receptor expression in premenopausal female cynomolgus monkeys.

DESIGN

Animals were randomized to receive diets with either casein lactalbumin or soy as the protein source for 12 months. Paired follicular and luteal mammary gland biopsies were taken before and after treatment and evaluated for epithelial proliferation and area, apoptosis, and sex steroid receptor expression.

SETTING

Academic research environment.

ANIMAL(S)

Fifty-two adult female cynomolgus monkeys (Macaca fascicularis).

INTERVENTION(S)

Soy protein with the human equivalent of 129 mg/d of isoflavones.

MAIN OUTCOME MEASURE(S)

Breast proliferation and epithelial area.

RESULT(S)

Follicular and luteal assessments were taken on cycle day (+/- SE) 5.3 +/- 0.1 and 22.0 +/- 0.1, respectively. Serum E2, serum P, breast proliferation, and vaginal maturation were significantly higher in the luteal vs. follicular phase. Soy treatment resulted in significantly higher serum isoflavone concentrations compared with the casein lactalbumin group but did not significantly affect breast proliferation, epithelial area, apoptosis, or progesterone receptor expression; uterine size; or vaginal maturation in either the follicular or luteal phase.

CONCLUSION(S)

Results indicate that dietary levels of soy intake have no detectable hormonal effects on the premenopausal breast.

Association of genetic polymorphisms with serum estrogens measured multiple times during a 2-year period in premenopausal women

There is evidence that circulating estrogens are associated with breast cancer risk. In this study of premenopausal women, we explored the association of polymorphisms in genes in the estrogen synthesis and metabolism pathways with serum and urinary levels of estrone (E1) and estradiol (E2) and with the urinary ratio of 2-hydroxyestrone (2-OHE1)/16alpha-hydroxyestrone (16alpha-OHE1). This analysis included 220 women, who were participants in a 2-year randomized soy intervention. Blood specimens were collected in the luteal phase of the menstrual cycle an average of 4.4 times over 2 years. Overnight urinary specimens were collected on the same cycle day, only at baseline. Levels of E1, E2, 2-OHE1, and 16alpha-OHE1 were measured by enzyme immunoassays. The DNA samples were analyzed by PCR/RFLP for the COMT Val158Met, CYP1A1*2A, CYP1A1*2B, CYP1A2*1F, CYP1B1 Val432Leu, and CYP17 T27C polymorphisms. We applied mixed models to investigate the relations between genotypes and repeated serum hormone measurements and generalized linear models to assess associations between genotypes and urinary estrogen metabolites. The CYP1A2 C allele was significantly associated with lower serum E2 levels; in CC genotype carriers, serum E2 levels were 26.3% lower than in homo- and heterozygous common allele carriers combined (P = 0.01). CYP1A2*1F also affected the urinary 2-OHE1/16alpha-OHE1 ratio; carriers of the variant C allele had a markedly lower ratio than individuals with the AA genotype (1.37 versus 1.76; P = 0.002). These data suggest that CYP1A2*1F is associated with lower circulating levels of E2, and that it may be a susceptibility locus for breast cancer.

A 2-year soy intervention in premenopausal women does not change mammographic densities

Soy consumption may be related to lower breast cancer risk as assessed by breast density. The aims of this 2-y trial were to examine the effects of soy foods and lifetime soy intake on mammographic density. After 220 premenopausal women were randomly assigned to the intervention or control group, the former group consumed 2 daily servings of soy foods equivalent to 50 mg of isoflavones and the latter consumed their regular diet. The respective dropout rates were 15.6 and 12.6%; adherence to the study regimen was high. We assessed lifetime soy intake with a questionnaire and measured breast density in screening mammograms obtained at baseline and at the end of the trial for 98 intervention and 103 control women using a computer-assisted method. None of the mammographic outcomes differed significantly by experimental group. The total area of the breast increased and the size of the dense areas decreased significantly over time in both groups. After 2 y, the mean percentage density had decreased by 2.8 and 4.1% in intervention and control women, respectively. Women who reported eating more soy during their lives had higher percentage densities than women whose diet included little soy; this difference was significant only in Caucasians. Lower soy intake during early life and higher soy intake during adulthood predicted a greater reduction in the percentage density during the study period. After 2 y of intervention, we observed no significant differences in mammographic densities by intervention status, but it appears that soy consumption throughout life may have some effect on breast density.