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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
(Oral Abstracts)Soy and Cancer
Soy Consumption and Cancer Risk : Human StudiesStimulatory Effects of Soy Protein Isolate on Breast Fluid Secretion.
Nicholas L. Petrakis and Stephen Barnes. University of California, San Francisco; University of Alabama, Birmingham, USA.Several epidemiologic studies reported that soy was protective against premenopausal breast cancer in Asian women. We evaluated the effect of prolonged ingestion of a commercial soy protein isolate (soy) on nipple aspirate fluid (NAF) in 24 women. We hypothesized that soy might alter the composition of nipple aspirate fluid (NAF).
At monthly visits for one year, 24 women, ages 30 to 58, underwent nipple aspiration, and gave blood and 24-hour urine samples. Months 1-3 and 10-12 were control periods. Beginning after visit 3 and continuing to visit 9, the women daily ingested 38 grams of soy containing 38 mg of genistein. Biomarkers included: statistically significant change in volume of NAF, GCDFP-15 concentration, and in the morphology of exfoliated epithelial cells in NAF. Plasma estradiol, progesterone, SHBG, prolactin, cholesterol, HDL-cholesterol, and triglyceride levels were determined. Compliance was assessed by urinary excretion of genistein and daidzein.
During soy ingestion, NAF volumes increased two- to six-fold in fourteen premenopausal women and in three postmenopausal women using replacement estrogen, but no change occurred in seven postmenopausal women not using estrogen. Of potential concern was the finding of hyperplastic epithelial cells in NAF in 7/24 women (29.2%) during the months on soy. Mean GCDFP-15 concentration decreased 30% in premenopausal women. No changes occurred in plasma concentrations of prolactin,
SHBG, cholesterol, HDL-cholesterol and triglyceride. Concentrations of plasma estradiol, but not progesterone, were erratically elevated through a "composite menstrual cycle" during the months on soy compared with those in the control periods.
The prolonged consumption of soy had a stimulatory effect on the premenopausal breast fluid secretion, presumed to be due to the phytoestrogens, genistein and daidzein, contained in the soy protein isolate.Soy Symposium Home http://soyfoods.com/symposium/
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