Soy Studies 2015-2023

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The Weston A. Price Foundation has main­tained a list of studies showing the adverse effects of soy and soy isoflavones on our Soy Alert! page at westonaprice.org.¹

We have recently updated this list to include all relevant studies published since 2015. A great thanks to Ana Jane Ivacove for compiling the list.

Soy foods had their heyday of promotion and propaganda in the early 2000s, with soy presented as a panacea for everything from hor­monal problems to osteoporosis. This hype has gone quiet as studies accumulate showing soy for what it is: an endocrine-disrupting poison.

STUDIES SHOWING ADVERSE EFFECTS OF SOY

2015: Studies compare soybean oil to coconut oil and find changes in gene expression and metabolite levels in the organs, particularly the liver, of soy-fed animals. “[Soy feeding] showed increased weight gain, larger fat deposits, a fatty liver with signs of injury, diabetes and insulin resistance, all of which are part of the Metabolic Syndrome.”²

2016: Soy foods increase the length of the female menstrual cycle. In men, soy consumption is linked with lower sperm concentration. Two case reports describe feminizing effects in men that occurred due to soy food consumption. This study is especially interesting because the author, Mark Messina, has been one of the most vocal and active promoters of soy.³

2017: Endocrine disruption manifests as a de­crease in testosterone levels, Sertoli cell number and an increase in the percentage of degenerated Sertoli and Leydig cells in animals receiving soy milk.⁴

2017: Animals fed with soy have difficulty with digestion and absorption, resulting in negative effects. The abnormality of intestinal cells nega­tively affects the immunity of animal intestines and causes death. “Studies have demonstrated that SBA [soybean agglutinin] can affect the integrity and permeability of cell membrane and decline in the cell proliferation in the intestinal epithelial cell line from piglets.”⁵

2018: Soybean protein (agglutinin) causes nega­tive effects on animal gut health by influenc­ing the intestinal structure, barrier function, mucosal immune system and the balance of the intestinal flora.⁶

2019: Studies investigating breast cancer sur­vivors find that those who consumed soy have a high risk of osteoporosis-related fractures.⁷

2020: Researchers find that soybean oils influ­ence the activity of the hypothalamus, causing genes not to function as expected. Abnormal changes are seen in the gene that produces oxytocin (a hormone that controls key aspects of the reproductive system, such as childbirth and lactation, and aspects of human behavior). Changes are noted in other genes associated with neurological ills such as anxiety, pain, depression or schizophrenia.⁸

2020: Researchers find dysregulation of the hypothalamic gene and oxytocinergic system by feeding soybean oil diets to male mice. “Genes were associated with inflammation, neuroendo­crine, neurochemical, and insulin signaling. Oxt was the only gene with metabolic, inflammation, and neurological relevance upregulated by both soybean oil diets compared to both control diets. Oxytocin immunoreactivity of the hypothala­mus was reduced. . . these central and peripheral effects of soybean oil diets were correlated with glucose intolerance but not body weight.”⁹

2021: This study finds that tofu consumption is associated with cognitive impairment and memory decline. One study has suggested ““that the detrimental effects of tofu on memory performance could be due to the use of formal­dehyde as a preservative.”¹⁰

STUDIES SHOWING ADVERSE EFFECTS OF SOY ISOFLAVONES

2015: Levels of soy isoflavones similar to those in infant formula fed to mice play a role in exposure to endocrine-disrupting chemicals (EDCs) associated with the obesity epidemic. “Obesogenic EDCs have the potential to inap­propriately stimulate adipogenesis and fat stor­age, influence metabolism and energy balance and increase susceptibility to obesity.”¹¹

2016: Exposure to soy-based infant formula results in negative effects on the long-term development of infants.¹²

2016: In a rat model, intake of soy (genistein) inhibits follicle development, disrupts the production of sex steroid hor­mones and alters the expression of steroidogenic enzymes. Like other phytoestrogens found in soy, this has the potential to mimic, enhance or impair the estradiol pathway, thereby altering ovarian follicle growth.¹³

2016: Data show a link between long-term soy consumption and Kawasaki disease (KD). Soy isoflavones play a role in this.¹⁴

2017: “Consumption [of isoflavones] by infants and small children is of particular concern because their hormone-sensitive organs, including the brain and reproductive system, are still undergoing sexual differentiation and maturation. Thus, their susceptibility to the endocrine-disrupting activities of soya phyto-oestrogens may be especially high.”¹⁵

2018: Early-life exposure to genistein, a naturally occurring component in soy formula, interferes with development of the reproductive system, produces changes in tissues that persist into adulthood, and may be related to menstrual pain.¹⁶

2018: Soy infant formula has negative effects on animals, including on sexual development and reproductive function, neurobehavioral devel­opment, immune function and thyroid function. This brings awareness associated with relevant abnormalities in children with congenital hy­pothyroidism.¹⁷

2019: Studies find that animal diets containing soy isoflavones result in behavioral issues, with negative impact on estrogen-regulated systems, as well as dominat­ing behavior and cognition.¹⁸

2019: A change in gender-related behavior in children and feminization is associated with soy consumption. In animals, the excessive phytoestrogen intake leads to derangements of fertility, sexual development and behavior. Phyto-endrocrines are called modulators or disruptors of the endocrine system.¹⁹

2019: Several studies show that the bioactive ingredient in soy changes the expression in several cell receptors of different tissues and cancer cells. Therefore, consumption of soy iso­flavones disrupts endocrine functions, such as thyroid function and reproductive performance (because of their similar structure to estrogens). Furthermore, changing their gene expression stimulates the sensitivity of cells or tissues to the effects of physiological functions, such as growth, development, osteogenesis, immune response, lipogenesis, reproductive process and anticarcinogenesis.²⁰

2020: High intake of soy and soy isoflavones in­creases the risk of prostate cancer. “During 16.9 years follow-up, we registered 221 deaths from prostate cancer. Isoflavones and soy products intake was associated with an increased risk of prostate cancer death.”²¹

2021: The metabolites of soy isoflavones play a role in the risk of development and recurrence of breast cancer and in interactions with drugs used for treating breast cancer.²²

2022: Worldwide collected data for over a de­cade show an increase in women diagnosed with breast cancer. A case report on the amount of isoflavone consumption and risk of breast cancer diagnosed in population indicates a strong cor­relation of isoflavone consumption and the risk of breast cancer.²³

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SIDEBAR

ESTROGENS IN SOYBEAN OIL

The most shocking discovery in our literature search was a 1999 analysis that we had missed. The researchers documented 28,370 ug estrogen in a tablespoon of soybean oil. Most birth control pills today contain between 20,000 ug and 30,000 ug estradiol. So, a tablespoon of soybean oil contains as much or more estrogen than most birth control pills. A serving of French fries, chicken nuggets or a pastry can easily contain one tablespoon of oil—and 80 percent of all oil used in processed and fast foods is soybean oil.

SOURCE: MacDonald, HB. When it comes to hormones and milk, please give it a rest. The Canadian Nurse. 1999, 95(10):5 www.proquest.com/openview/b995bb7d22da49a80068bb1afa254603/1?pq-origsite=gscholar&cbl=41610.

REFERENCES

1. https://www.westonaprice.org/soy-alert/
2. Nealon S. Soybean oil may be more fattening than fructose or coconut oil. University of California-Riverside, Jul. 22, 2015. https://www.universityofcalifornia.edu/news/soybean-oil-may-be-more-fattening-fructose-or-coconut-oil
3. Messina M. Soy and health update: evaluation of the clinical and epidemiologic literature. Nutrients. 2016;8(12):754.
4. Nardi J, Moras PB, Koeppe C et al. Prepubertal subchronic exposure to soy milk and glyphosate leads to endocrine disruption. Food Chem Toxicol. 2017;100:247-252.
5. Pan L, Zhao Y, Yuan Z et al. The integrins involved in soybean agglutinin-induced cell cycle alterations in IPEC-J2. Mol Cells. 2017;40(2):109-116.
6. Pan L, Farouk MH, Qin G et al. The influences of soybean agglutinin and functional oligosaccharides on the intestinal tract of monogastric animals. Int J Mol Sci. 2018;19(2):554.
7. Zheng N, Hsieh E, Cai H et al. Soy food consumption, exercise, and body mass index and osteoporotic fracture risk among breast cancer survivors: the Shanghai Breast Cancer Survival Study. JNCI Cancer Spectr. 2019;3(2):pkz017.
8. America’s most widely consumed oil causes genetic changes in the brain. ScienceDaily, Jan. 17, 2020. https://www.sciencedaily.com/releases/2020/01/200117080827.htm
9. Deol P, Kozlova E, Valdez M et al. Dysregulation of hypothalamic gene expression and the oxytocinergic system by soybean oil diets in male mice. Endocrinology. 2020;161(2):bqz044.
10. Svensson T, Sawada N, Mimura M et al. Midlife intake of the isoflavone genistein and soy, and the risk of late-life cognitive impairment: the JPHC Saku Mental Health Study. J Epidemiol. 2021 Dec 18.
11. Stel J, Legler J. The role of epigenetics in the latent effects of early life exposure to obesogenic endocrine disrupting chemicals. Endocrinology. 2015;156(20):3466-3472.
12. Yu J, Bi X, Yu B et al. Isoflavones: anti-inflammatory benefit and possible caveats. Nutrients. 2016;8(6):361.
13. Patel S, Peretz J, Pan YX et al. Genistein exposure inhibits growth and alters steroidogenesis in adult mouse antral follicles. Toxicol Appl Pharmacol. 2016;293:53-62.
14. Portman MA, Navarro SL, Bruce ME et al. Soy isoflavone intake is associated with risk of Kawasaki disease. Nutr Res. 2016;36(8):827-834.
15. Patisaul HB. Endocrine disruption by dietary phyto-oestrogens: impact on dimorphic sexual systems and behaviours. Proc Nutr Soc. 2017;76(2):130-144.
16. Pasley J. Study links soy formula feeding and menstrual pain. VUMC Reporter, Dec. 13, 2018. https://news.vumc.org/2018/12/13/study-links-soy-formula-feeding-and-menstrual-pain/
17. Testa I, Salvatori C, Di Cara G et al. Soy-based infant formula: are phyto-oestrogens still in doubt? Front Nutr. 2018;5:110.
18. Mallien AS, Soukup ST, Pfeiffer N et al. Effects of soy in laboratory rodent diets on the basal, affective, and cognitive behavior of C57BL/6 mice. J Am Assoc Lab Anim Sci. 2019;58(5):532-541.
19. Yang J, Wen L, Jiang Y et al. Natural estrogen receptor modulators and their heterologous biosynthesis. Trends Endocrinol Metab. 2019;30(1): 66-76.
20. Xiao CW, Wood C, Gilani GS. Nuclear receptors: potential biomarkers for assessing physiological functions of soy proteins and phytoestrogens. J AOAC Int. 2006;89(4):1207-1214.
21. Sawada N, Iwasaki M, Yamaji T et al. Soy and isoflavone consumption and subsequent risk of prostate cancer mortality: the Japan Public Health Center-based Prospective Study. Int J Epidemiol. 2020;49(5):1553-1561.
22. Hatono M, Ikeda H, Suzuki Y et al. Effect of isoflavones on breast cancer cell development and their impact on breast cancer treatments. Breast Cancer Res Treat. 2021;185(2):307-316.
23. Boutas I, Kontogeorgi A, Dimitrakakis C et al. Soy isoflavones and breast cancer risk: a meta-analysis. In Vivo. 2022;36(2):556-562.

This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly journal of the Weston A. Price Foundation, Summer 2023

 

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