More on the Soy Debate
Townsend Letter for Doctors and Patients July 2004

Letter to the EditorEditor:
As an update to the ongoing debate on soy foods, we have compiled two lists of studies showing adverse effects of soy. One lists adverse effects of isoflavones in soy in studies from 1953 to the present. The other lists adverse effects from soy foods in general in studies from 1971 to the present. Altogether we found over 150 studies showing adverse effects, most of which have been published in well-known journals. They are posted on our website at www.westonaprice.org under Soy Alert!
 
Several interesting trends emerge from this exercise. One is the large number of studies that are recent, having been published during the last few years. We have been criticized for citing studies that were "too old." We did so to show that knowledge of soy toxicity dates back many decades. These older studies are entirely supported by more recent research, which confirms earlier discoveries that soy is an endocrine disrupter and a goitrogen. Secondly, evidence of the carcinogenic and mutagenic nature of soy isoflavones has emerged from recent research. Isoflavones have been found to be highly damaging to DNA.
 
A third trend is the accumulation of evidence that soy inhibits tyrosine kinase. The enzyme is involved in mediating the response of cells to the body's growth factors. It is also involved in critical nerve responses dealing with memory and possibly speech. This may explain the 1999 findings of Lon White who noted increased cognitive problems in elderly people who regularly consumed a moderate amount of soy products. Some of the more important recent studies are posted below:
 
1998. Morris SM and others, p53, mutations, and apoptosis in genistein-exposed human lymphoblastoid cells. MutatRes 1998Aug31;405(l):41-56.In vitro administration of genistein was found to cause cellular damage and death. "Our results may be interpreted that genistein is a chromosomal mutagen..."
1998. Santti R and others. Phytoestrogens: Potential Endocrine Disrupters in Males. Toxicolind Health 1998 Jan-Apr;14(l-2):223-37. In doses comparable to the daily intake from soy-based feed, isoflavonoids such as genistein were estrogen agonists in the prostate of adult laboratory rodents. When given neonatally, no persistent effects were observed. In contrast, the central nervous system (CHS)-gonadal axis and the male sexual behavior of the rat appear to be sensitive to phytoestrogens during development. The changes were similar but not identical to those seen after neonatal treatment with DES, but higher doses of phytoestrogens were needed.
1998. Setchell KD and others. Isoflavone content of infant formulas and the metabolic fate of these early phytoestrogens in early life. Am J Clin Nutr1998 Dec;68 (6 Suppl):1453S-1461S. Noting the results of an earlier study which found that plasma isoflavone levels in infants fed soy-based formula were 13,000-22,000 higher than concentrations found in fed breast milk or milk-based formula, the authors explain these high levels as due to "...reduced intestinal bio-transformation, as evidenced by low or undetectable concentrations of equol and other metabolites, and is maintained by constant daily exposure from frequent feeding." The authors assert that these unnaturally high levels of isoflavones in the bloodstream of soy-fed children "may have long-term health benefits for hormone-dependent diseases."
1998. McMichael-Phillips DF and others. Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast. Am J Clin Nutr 1998 Dec;68(6 Suppl):1431S-1435S. Forty-eight women with benign or malignant breast disease were randomly assigned a normal diet either alone or with a 60 gram soy supplement containing 45 mg isoflavones, taken for 14 days. The proliferation rate of breast lobular epithelium significantly increased after just 14 days of soy supplementation when both the day of menstrual cycle and age of patient were accounted for. Thus short-term dietary soy containing isoflavone levels found in modern soy foods stimulates breast proliferation.
1998. Strauss and others. Genistein exerts estrogen-like effects in male mouse reproductive tract. Mol Cell Endocrinal 1998 Sept 25:144(1-2) 83- 93. Genistein was found to have estrogenic effects in adult male mice, at doses comparable to those present in soy-based human diets. "In neonatal animals, considerably higher doses are required to show estrogen-like activity."
1999. Casanova M and others. Developmental effects of dietary phytoestrogens in Sprague-Dawley rats and interactions of genistein and daidzein with rat estrogen receptors alpha and beta in vitro. Toxicol Sci 1999 0ct;51(2):236-44. Effects of dietary genistein included a decreased rate of body-weight gain, a markedly increased (2.3 fold) uterine/body weight and a significant acceleration of puberty among females.
1999. Fisher JS and others. Effect of neonatal exposure to estrogenic compounds on development of the excurrent ducts of the rat testis through puberty to adulthood. Environ Health Perspect 1999 ay;107(5):397-405. Administration of genistein to rats caused minor but significant changes in rat testes. "This study suggests that structural and functional...development of the excurrent ducts is susceptible to impairment by neonatal estrogen exposure, probably as a consequence of direct effects. The magnitude and duration of adverse changes induced by treatment with a range of estrogenic compounds was broadly comparable to their estrogenic potencies reported from in vitro assays."
1999. Kulling SE and others. The phytoestrogens coumoestrol and genistein induce structural chromosomal aberrations in cultured human peripheral blood lymphocytes. Arch Toxicol 1999 Feb;73(l):50-4. Exposure of blood lymphocytes to low levels of genistein in vitro caused chromosomal aberrations including chromatid breaks, gaps and interchanges. Exposure to daidzein did not cause aberrations, even at high levels. The results suggest that "...some but not all phytoestrogens have the potential for genetic toxicity."
1999. Abe T. Infantile leukemia and soybeans - a hypothesis. Leukemia 1999 Mar;13(3)317-20. Genistein from soybeans contributes to DNA strand breaks and may be "largely responsible" for infantile acute leukemia.
1999. Hilakavi-Clarke and others Exposure to genisten during pregnancy increases carcinogen- induced mammary tumorigenesis in female rat offspring. Oncol Rep 1999 Sep-Oct:6(5):1089-95. Dietary erenistein was found to enhance the growth of mammary gland tumors in mice. The results suggest "...that a maternal exposure to subcutaneous administration of genistein can increase mammary tumorigenesis in the offspring, mimicking the effects of in utero estrogen exposures."
1999. Eklund G and Oskarsson A. Exposure of cadmium from infant formulas and weaning foods. Food Addit Contam 16(12):509-19 (1999). Cadmium was 6 times higher in soy formulas than cow's milk formulas.
1999. Olguin MC and others. Intestinal alterations and reduction of growth in prepuberal rats fed with soybean [Article in Spanish]. Medicina (BAires) 1999;59:747-752. Rats fed soy-based chow had reduced growth and an increase in gastrointestinal problems compared to controls.
1999. NilhausenK and Meinertz H. Lipoprotein(a) and dietary proteins; casein lowers lipoprotein(a) concentrations as compared with soy protein. Am J Clin Nutr 1999;69:419-25. Many studies have shown that soy consumption can lower serum cholesterol levels. These studies have led to claims that soy can prevent heart disease. However, the theory that high cholesterol levels cause heart disease is becoming more and more untenable. Cholesterol levels are not a good marker for proneness to heart disease. However Lipoprotein(a) or Lp(a), does serve as a good marker for heart disease. This study indicates that soy raises Lp(a), meaning that it is likely to contribute to heart disease.
1999. White L. Association of High Midlife Tofu Consumption with Accelerated Brain Aging. Plenary Session #8: Cognitive Function, The Third International Soy Symposium, Program, November 1999, page 26. An ongoing study of Japanese Americans living in Hawaii found a significant statistical relationship between two or more servings of tofu per week and " accelerated brain aging." Those participants who consumed tofu in mid life had lower cognitive function in late life and a greater incidence of Alzheimer's and dementia.
2000. Cassanova N and others. Comparative effects of neonatal exposure of male rats to potent and weak (environmental) estrogens on spermatogenesis at puberty and the relationship to adult testis size and fertility: evidence for stimulatory effects of low estrogen levels. Endocrinology 2000 0ct;141(10):3898- 907. Administration of genistein to rats significantly retarded most measures of pubertal spermatogenesis. Animals fed a soy-free diet had significantly larger testes than controls fed a soy-containing diet. "It is concluded that...the presence or absence of soy or genistein in the diet has significant short-term (pubertal spermatogenesis) and long-term (body weight, testis size, FSH levels and possibly mating) effects on males."
2000. Watanabe S and others. Effects of isoflavone supplement on healthy women. Biofactors 2000;12 (l-4):233-41. After one month of taking 20 mg or 40 mg isoflavones daily, 60% of the young women had prolonged menstruation, 20% had shortened menstruation, 17% remained unchanged and 3% became irregular. Other hormonal changes "suggest that isoflavones influence not only estrogen receptor-related functions but the hypothalamo-hypophysis-gonadal axis."
2000. Salti Gl and others. Genistein induces apoptosis and topoisomerase ll-mediated DNA breakage in colon cancer cells. Eur J Cancer 2000 Apr;36(6):796-802. DNA breakage in colon cancer cells occurred within I hour of treatment with genistein.
2000. Lephard ED and others. Phytoestrogens decrease brain calcium- binding proteins but do not alter hypothalamic androgen metabolizing enzymes in adult male rats. Brain Res 2000 Mar 17;859 (1): 123-31. Animals fed diets containing phytoestrogens for 5 weeks had elevated levels of phytoestrogens in the brain and a decrease of brain calcium-binding proteins. Calcium-binding proteins are associated with protection against neuro degenerative diseases.
2000. Strick R and others. Dietary bioflavonoids induce cleavage in the MLL gene and may contribute to infant leukemia. Proc Natl Acad Sci USA 2000 Apr 25;97(9):4790-5. Researchers found that flavonoids, especially genistein, can cross the placenta and induce cell changes that lead to infant leukemia.
2000. Chang HS and Doerge DR. Dietary genistein inactivates rat thyroid peroxidase in vivo without an apparent hypothyroid effect. Toxicol Appl Pharmacol 2000 Nov l;168(3):244- 52. The activity of thyroid peroxidase activity in soy-fed rats was reduced by up to 80% compared to those on a soy- free diet. As thyroid hormone levels and thyroid weights were no different between treated and untreated groups, the researchers concluded that "the remaining enzymatic activity is sufficient to maintain thyroid homeostasis in the absence of additional perturbations." However, it is difficult or impossible to measure some of the more subtle manifestations of hypothyroidism in rats.
2000. Gee JM and others. Increased induction of aberrant crypt foci by 1,2-dimethylhydrazine in rats fed diet containing purified genistein or genistein-rich soya protein. Carcinogenesis 2000;21:2255-2259. Rats fed the isoflavone genistein exhibited pathological changes in the colon.
2000. Ikeda T and others. Dramatic synergism between excess soybean intake and iodine deficiency on the development of rat thyroid hyperplasia. Carcinogenesis 2000 Apr;21(4):707-13. Excess sodium intake with iodine deficiency caused abnormal growth of the thyroid gland.
2007. Nagata C and others. Inverse association of soy product intake with serum androgen and estrogen concentrations in Japanese men. Nutr Cancer 2000;36(l):14-8. Researchers found lower testosterone levels and higher estrogen levels in Japanese men consumed higher levels of soy foods.
2000. Flynn KM and others. Effects of genistein exposure on sexually dimorphic behaviors in rats. Toxicol Sci 2000 Jun;55(2):311-9. Noting that genistein "has adverse effects on animal reproduction," the researchers administered genistein to pregnant rats and to their offspring during growth. Results indicated significantly decreased body weight in genistein-fed rats compared to controls. The results indicate that developmental genistein treatment, at levels that decrease maternal and offspring body weight, causes subtle alternations in some sexually dimorphic behaviors.
2000. Habito RC and others. Effects of replacing meat with soya bean in the diet on sex hormone concentrations in healthy adult males. Br J Nutr 2000 0ct;84(4):557-63. Men consuming tofu instead of meat for 4 weeks had lower testosterone- oestradiol ratios as well as changes in other hormone levels. "Thus, replacement of meat protein with soyabean protein, as tofu, may have a minor effect on biologically-active sex hormones which could influence prostate cancer risk."
2000. Pino AM and others. Dietary isoflavones affect sex hormone-binding globulin levels in postmenopausal women. J Clin Endocrinol Metah 2000;85:2797-2800. Soy consumption increased sex hormone-binding globulin (SHGB) levels in postmenopausal women were evidence of endocrine disruption.
2000. Quella SK and others. Evaluation of soy phytoestrogens for the treatment of hot flashes in breast cancer survivors: A North Central Cancer Treatment Group Trial. J Clin Oncol 2000 Mar;18(5): 1068-1074. Soy did not relieve hot flashes in breast cancer survivors.
2000. "Clarkson TB. Soy phytoestrogens: what will be their role in postmenopausal hormone replacement therapy? Menopause 2000 Mar-Apr;7(2):71-5. Soy did not prevent bone loss when measured at autopsy in female monkeys who had had their reproductive organs removed.
2000. North K and Golding J. Vegetarian diet in pregnancy linked to birth defect. British Journal of Urology International, 2000 Jan; 85:107-113. Mothers who ate a vegetarian diet during pregnancy had a fivefold greater risk of delivering a boy with hypospadias, a birth defect of the penis. The authors of the study suggested that the cause was greater exposure to phytoestrogens in soy foods popular with vegetarians.
2001. Badger TM and others. Developmental effects and health aspects of soy protein isolate, casein, and whey in male and female rats. Int J Toxicol 2001 May-Jun;20(3);165-74. Feeding of soy protein isolate was found to accelerate puberty in female rats. Female rats also had reduced serum 17beta-estradiol concentrations.
2001. Doerge DR and others. Placental transfer of the soy isoflavone genistein following dietary and gavage administration to Sprague Dawley rats. Reprod Toxicol 2001 Mar-Apr;15(2): 105-10. Genistein was found to cross the rat placenta and reach the fetal brain in doses similar to those observed in humans.
2001. Newbold RR and others. Uterine adenocarcinoma in mice treated neonatally with genistein. Cancer Res 2001 Jun l;61(ll):4325-8. Genistein in soy was found to be more carcinogenic than DES, especially during "critical periods of differentiation... the use of soy-based infant formulas in the absence of medical necessity and the marketing of soy products designed to appeal to children should be closely examined."
2001. Declos KB and others. Effects of dietary genistein exposure during development on male and female DC (Sprague-Dawley) rats. Reprod Toxicol 2001Nov;15(6):647-63. Genistein was administered to rats at various concentrations starting on gestation day 7 and continuing throughout pregnancy, lactation and growth of the pups to day 50. The genistein-fed rats showed a number of variances from the norm: lower weight in both sexes; decreased prostate weight in males; higher pituitary gland to body weight ratios in both sexes; hyperplasia of the mammary glands, abnormal ovarian antral follicles and abnormal cellular maturation in the vagina in females; aberrant or delayed spermatogenesis and deficit sperm in males; and an increase in the incidence and/or severity of renal tubal mineralization in both sexes, even at low doses. "Dietary genistein thus produced effects in multiple estrogen-sensitive tissues in males and females that are generally consistent with its estrogenic activity. These effects occurred within exposure ranges achievable in humans."
2001. Thigpen JE and others. Effects of the dietary phytoestrogens daidzein and genistein on the incidence of vulvar carcinomas in 129/J mice. Cancer Detect Prev 2001;25(6):527-32. Within one month, the incidence of vulvar carcinomas in mice fed a modified soy protein diet was significantly increased over those of mice fed control diets. Within three months, the incidence of vulvar carcinomas in mice fed the soy protein diet was significantly increased over those of mice fed other control diets. "We concluded that dietary levels of daidzein and genistein were associated with an increase in the incidence of vulvar carcinomas in mice..."
2001. de Lemos ML. Effects of soy phytoestrogens genistein and daidzein on breast cancer growth. Ann Pharmacother 2001 Sep;35(9):118-21. "Genistein and daidzein may stimulate existing breast tumor growth and antagonize the effects of tomoxifen. Women with current or past breast cancer should be aware of the risks of potential tumor growth when taking soy products."
2001. Ju YH and others. Physiological concentrations of dietary genistein dose-dependently stimulate growth of estrogen-dependent human breast cancer (MCF-7) tumors implanted in athymic nude mice. J Nutr 2001 Nov;131(ll):2957-62. Genistein stimulated breast tumor growth and cell proliferation in mice in a dose-responsive manner.
2001. Zhang QH and others. Inhibitory effect of genistein on the proliferation of the anterior pituitary cells of rats. Sheng Li Xue Bao 2001 Feb;53(l):51-4. Genistein inhibits proliferation and causes apoptosis of pituitary cells by inhibiting female rats of neonatal exposure to genistein. Reprod Toxicol 2001 Jul-Aug;15(4):399-411. Feeding of genistein to newborn rats resulted in lower body weight in male and female rats, estrous cycle irregularities and lowered fertility in female rats. Neonatal exposure to genistein caused dysfunction of postpubertal reproduction performance as well as abnormal development of gonads in female but not in male rats.
2001. Bennetau-Pelissero C and others. Effect of genistein-enriched diets on the endocrine process of gametogenesis and on reproduction efficiency of the rainbow trout Oncorhynchus mykiss. Gen Comp Endocrinol 2001 Feb;121(2):173-87. Genistein caused a decrease in testosterone levels in rainbow trout. Testicular development was accelerated in genistein-fed fish and sperm motility and concentration were decreased in a dose-dependent manner at spawning.
2001. Patisual HE and others. Soy isoflavone supplements antagonize reproductive behavior and estrogen receptor alpha- and beta-dependent gene expression in the brain. Endocrinology 2001 Jul;142(7):2946-52. Soy isoflavones interfere with estrogen receptors in the adult female rat brain resulting in a significant decrease in receptive behavior in estrogen- and progesterone-primed females. "The observed of sexual receptivity by the isoflavone supplement is probably due to antiestrogenic effects observed in the brain."
2001. Shibayama T and others. Neonatal exposure to genistein reduces expression of estrogen receptor alpha and androgen receptor in testes of adult mice. Endocr J 2001 Dec;48(6):655-63. "Our results exhibited that the disruption of gene expression continued for long term such as 3 months after administration of genistein, even if no effect was found at conventional reproductive-toxicological levels. We have shown that neonatal administration of weak estrogenic compound (genistein) affects male reproductive organs at molecular levels in adulthood."
2001. Lephart ED and others. Dietary soy phytoestrogen effects on brain structure and aromatase in Long-Evans rats. Neuroreport 2001 Nov 16;12(16):3451-5. Dietary phyto-estrogens significantly decrease body and prostate weights and during adulthood significantly change the structure of the sexually dimorphic brain region in male but not in female rats.
2001. Alfred CD and others. Soy diets containing varying amounts of genistein stimulate growth of estrogen-dependent (MCF-7) tumors in a dose-dependent manner. Cancer Res 2001 Jul l;61(13):5045-50. Soy protein isolates containing increasing concentrations of genistein stimulate the growth of estrogen-dependent breast cancer cells in vivo in a dose-dependent manner.
2001. Alfred CD and others. Dietary genistin stimulates growth of estrogen-dependent breast cancer tumors similar to that observed with genistein. Carcinogenesis 2001 0ct;22(10):1667-73. Genistin, the glycoside form of genistein, is converted to genistein by human saliva. The glycoside genistin, like the aglycone genistein, can stimulate estrogen-dependent breast cancer cell growth in vivo. Removal of genistin or genistein from the diet caused tumors to regress.
2001. Strom BL and others. Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood. JAMA 2001 Nov 21;286(19):2402-3. Although reported in the media as a vindication of soy infant formula, the study actually found that soy-fed infants had more reproductive problems and more asthma as adults.
2001. Massey LK and others. Oxalate content of soybean seeds (Glycine max: Leguminosae), soyfoods, and other edible legumes. JAgric Food Chem 2001 Sep;49(9):4262-6. Soyfoods were found to be high in oxalates and likely to contribute to kidney stones.
2002. Jefferson W and others. Assessing estrogenic activity of phytochemicals using transcriptional activation and immature mouse uterotrophic responses. J Chromatogr B Analyt Technol Biomed Life Sci 2002 Sep 25;777(l-2):179. Genistein caused an increase in uterine weight and several other indications of estrogenicity.
2002. Doerge D and Chang K Inactivation of thyroid peroxidase soy isoflavones, in vitro and in vivo. Chromatogr B Analyt lkchnol Biome>Life Sci 2002 Sep 25;777(l-2):269. The paper reviews the evidence in human and animals for anti-thyroid effects of soy and its principal isoflavones, genistein and daidzein. Genistein interferes with estrogen receptors in rat prostate glands which "...may have implications for reproductive toxicity and carcinogenesis that warrant further investigation."
2002. Whitehead SA and others. Acute and chronic effects of genistein, tyrphostin and lavendustinA on steroid synthesis in luteinized human granulosa cells. Hum Reprod 2002 Mar;17(3):589-94. Genistein directly inhibits steroid-production enzymes.
2002. Ju YH and others. Dietary genistein negates the inhibitory effect of tamoxifen on growth of estrogen-dependent human breast cancer (MCF- 7) cells implanted in athymic mice. Cancer Res 2002 May l;62(9):2474-7. Dietary genistein negated or overwhelmed the inhibitor effect of tamoxifen on tumor growth in ovariectomized and athymic mice. "Therefore, caution is warranted for postmenopausal women consuming dietary genistein while on TAM therapy for E-responsive breast cancer."
2002. Guo TL and others. Genistein modulates splenic natural killer cell activity, antibodv-forming cell response and phenotypic marker expression in F(0) and F(l) generations of Sprague-Dawley rats. Toxicol Appl Pharmacol 2002 Jun 15;181(3):219-27. Genistein caused a decrease in the percentage of helper T cells and an increase in the relative weights of spleen and thymus in rats.
2002. Whitten PL and others. Neurobehavioral actions of coumestrol and related isoflavonoids in rodents. Neurotoxicol Teratol 2002 Jan- Feb;24(l):47-54. Coumestrol and related isoflavones induced neurobehavioral actions in rodents that were antiestrogenic, either antagonizing or producing an action in opposition to that of estradiol. "This work demonstrates that even small, physiologically relevant exposure levels can alter estrogen-dependent gene expression in the brain and complex behavior."
2002. Nicholls J and others. Effects of soy consumption on gonadotropin secretion and acute pituitary responses to gonadotropin-releasing hormone in women. J Nutr 2002Apr;132(4):708-14. Twelve women consumed 60 mg isoflavones daily for 10-14 days. A residual postmenopausal effect was seen in postmenopausal subjects. "In one premenopausal woman, enhanced LH secretion was observed after soy treatment, suggesting there may be sub-populations of women who are highly sensitive to isoflavones."
2002. Kumar NB others. The specific role of isoflavones on estrogen metabolism in premenopausal women. Cancer 2002 Feb 15;94(4):1166-74. Sixty eight women consuming 40 mg soy isoflavones daily for 12 weeks had changes in steroid hormones and increased cycle length.
2002. Sharp RM and others. Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity. Hum Reprod 2002 Jul;17(7):1692-703. Infant male marmoset monkeys were fed either soy-based or milk-based formula. The neonatal testosterone rise was suppressed in the soy-fed monkeys. Levels of isoflavone in the monkey diets were 40-87% of that reported in 4- month human infants fed a 100% soy- based formula diet. "It is therefore considered likely that similar, or larger, effects to those shown here in marmosets may occur in human male infants fed with SFM [soy formula milk]."
2002. Chiang, CE and others. Genistein Inhibits the Inward Rectifying Potassium Current in Guinea Pig Ventricular Myocytes. J Biomed Sci 2002;9:321-326. Dietary isoflavones genistein dose-dependently and reversibly inhibit the inward rectifying K+ (potassium) current in guinea pigs ventricular myocytes, suggesting the potential for soy isoflavones to cause heart arrhythmias.
2002. Yellaya S and others. The phytoestrogen genistein induces thymic and immune changes: a human health concern? Proc Natl Acad Sci USA 2002 May 28;99(ll):7616-21. Genistein injections in ovariectomized adult mice produce dose-responsive decrease in thymic weight of up to 80%. Genistein decreased thymocyte numbers up to 86% and doubled apoptosis. There was a corresponding reduction in splenic cells. The dose that caused significant thymic and immune changes in mice was comparable to those reported in soy-fed human infants. "These results raise the possibility that serum genistein concentrations found in soy-fed infants may be capable of producing thymic and immune abnormalities, as suggested by previous reports of immune impairments in soy-fed infants."
2002. Lephard ED and others. Neurobehavioral effects of dietary soy phytoestrogens. Neurotoxicol Teratol 2002 Jan-Feb;24(l):5-16. Male mice fed diets rich in phytoestrogens had lower levels of maze performance than male mice fed diets free of phytoestrogens. (Opposite results were observed in female mice.) The results indicate that consumption of dietary phytoestrogens resulting in very high plasma isoflavone levels (in many cases over a relatively short interval of consumption in adulthood) can significantly alter sexually dimorphic brain regions, anxiety, learning and memory.
2002. Newbold R and others. Increased uterine cancer seen in mice injected with genistein, a soy estrogen, as newborns. Cancer Research 2002 Jun l;61(ll):4325-8. Infant mice given genistein developed cancer of the uterus later in life. "The data suggest that genistein is carcinogenic if exposure occurs during critical periods in a young animal's development."
2002. Khalil DA and others. Soy protein supplementation increases serum insulin-like growth factor-I in young and old men but does not affect markers of bone metabolism. J Nutr 2002 Sep;132(9):2605-8. Men consuming soy protein had higher levels of insulin-like growth factor-I (IGF-I) than those consuming milk protein. According to many other studies (but not stated in the report), high levels of IGF-I are also found in rBGH milk and have been implicated in causing hormonal cancers.
 
Sally Fallen, President
The Weston A. Price Foundation
westonaprice@msn.com
 
Mary G. Enig, PhD, FACN Vice President
The Weston A. Price Foundation
MGEnig@aol.com