Studies Showing Adverse Effects of Dietary Soy, 1939-2014

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Additional Studies: For a list of studies showing the toxicity of soy in the US Food & Drug Administration’s Poisonous Plant Database, see FDA Soy References. Also see http://toxicstudylist.blogspot.com and http://fetaltoxic.blogspot.com.

Dietary Soy Study Summaries

1939
Sharpless GR and others. Production of goiter in rats with raw and with treated soybean flour.  J Nutr 17 (Jun), 545-55. Unprocessed soybean flour, when fed as part of a diet over seven weeks to rats, makes the thyroid grow to four times its usual size. In addition the amount of iodine required by a rat on this diet is twice the normal amount.

1941
Wilgus HS and others. The goitrogenicity of soybeans. J Nutr, 22, 43-52.  The study found that soybeans are disruptive to the proper functioning of thyroids causing goiters in chicks. When the consumption of soybean oil meal increased from 30% to 60% of their diet, the goiters doubled in size.

1951
Almquist HJ and Merrit JB. Effect of Soybean Antitrypsin on Growth of the Chick. Arch Biochem, 35, 352-4. Raw soybean meal in amounts as small as 5% of daily protein intake in chicks was responsible for close to “maximal growth retardation.”

1952
Pritchard WR and others. Aplastic Anemia of Cattle Associated with Ingestion of Trichloroethylene-Extracted Soybean Oil Meal (Stockman Disease, Duren Disease, Brabant Disease). J Am Vet Med Assoc. 1952 Jul;121(904):1-8. The study was conducted across 44 herds (a total of 1776 cattle), using varying amounts trichloroethylene-extracted soybean oil meal as feed. In most cases calves under six months who were fed 1-3 lbs per day were the first to die from Aplastic anemia. In some cases they died in under fives weeks of consumption. Lacatation females also experienced a mortality rate that was considerably higher. Adults 24 months and older who ate between 1-4 lbs of the feed per day experienced an average 21% death rate.

1953
Liener IE. Soyin, a toxic protein from the soybean. I. Inhibition of rat growth. J Nutr, 49, 527-39. Soyin, in levels intended to simulate unheated soy flour, after being fed to rats was found to possibly cause “an enforced limitation of food intake with a consequent impairment of growth.”

1953
Eveleth DF and others. Toxicosis of chickens caused by trichloroethylene-extracted soybean meal. J Am Vet Med Assoc, 123, 38-9. During the fifty day period the death rate of birds fed the soybean meal was 26.3%, the death rate of the control group was 4.8%. Of the remaining birds after the 50 day period the average weight of the control group was 1.12 lbs while the weight for those fed the soybean meal was .78 lbs.

1959
Shepard T. Feeding of Soybean and Development of Goiter. Pediatrics 1959;24;854. The author took three cases of goiters in children in which the “thyroid enlargement (was) apparently related to intake of a soybean milk.” Two of the three children were switched to solid food and cows milk and their goiters grew smaller.

1959
Van Wyck JJ and other. The Effects Of A Soybean Product On Thyroid Function In Humans. Pediatrics, 24, 752-60. The study analyzes the effects of soy infant formula, showing that goiters and hypothyroidism are known to occur after consumption. The hindrance of thyroid hormone synthesis cause people to have to increase their intake of iodine. In the case of one child the hypothyroidism was cured by drinking whole cows milk instead of the soy.

1967
Gorill ADL and others. Exocrine pancreatic secretions by calves fed soybean and milk diet proteins. J Nutr, 92(1), 256. Calves fed the milk protein gained an average of 78 grams of weight per day while the calves fed the soy lost an average of 75 grams of weight per day. Those consuming soy protein also experienced a reduced flow rate and reduced levels of protein, trypsin and chemotrypsin in their pancreatic juice. “The soybean flour used in this experiment exerted a marked depression on exocrine pancreatic function of calves, which was detected after the animals had received the high soy diet for 2-5 days.”

1970
Jensen L and others. A Foot Pad Dermatitis in Turkey Poults Associated with Soybean Meal. Poultry Sci, 49, 76-82. There was a frequents occurrence of foot pad dermatis in Turkeys fed soybean meal poults, whereas the occurrence was rare in turkeys fed a diet containing casein, gelatin and corn.

1971
Wallace, GM. Studies on the Processing and Properties of Soymilk. J Sci Food Agri 1971 Oct;22:526-535. In order to neutralize the protease inhibitors (enzymes that inhibit the digestion of protein) in soy, it must be heated to very high temperatures under pressure and for considerable time. This process unfortunately denatures the overall protein content of soy, rendering it largely ineffective.

1974
Joseph, JR. Biological and physiological Factors in Soybeans. JOACS, 1974 Jan;51:161A-170A. In feeding experiments, use of soy protein isolate (SPI) increased requirements for vitamins E, K, D and B12 and created deficiency symptoms of calcium, magnesium, manganese, molybdenum, copper, iron and zinc.

1975
Nutrition during Pregnancy and Lactation. California Department of Health, 1975. Soy is listed as a minor source of protein in Japanese and Chinese diets. Major sources of protein listed were meat including organ meats, poultry, fish and eggs.

1976
Searle CE, ed, Chemical Carcinogens, ACS Monograph 173, American Chemical Society, Washington, DC, 1976. Asians throughout the world have high rates of thyroid cancer.

1977
Chang KC, ed, Food in Chinese Culture: Anthropological and Historical Perspectives, New Haven, 1977. This survey found that soy foods accounted for only 1.5 percent of calories in the Chinese diet, compared with 65 percent of calories from pork.

1978
FDA ref 72/104, Report FDABF GRAS – 258. In 1972, the Nixon administration directed a reexamination of substances believed to be GRAS in the light of any scientific information then available. This reexamination included casein protein which became codified as GRAS in 1978. In 1974, the FDA obtained a literature review of soy protein because, as soy protein had not been used in food until 1959 and was not even in common use in the early 1970s, it was not eligible to have its GRAS status grandfathered under the provisions of the Food, Drug and Cosmetic Act.

1979
Evaluation of the Health Aspects of Soy Protein Isolates as Food Ingredients. Prepared for FDA by Life Sciences Research Office, Federation of American Societies for Experimental Biology, 9650 Rockville Pike, Bethesda, MD 20014, Contract No, FDA 223-75-2004, 1979. In this document, the FDA expresses concern about nitrites and lysinoalanine in processed soy. Even at low levels of consumption–averaging one-third of a gram per day at the time–the presence of these carcinogens was considered too great a threat to public health to allow GRAS status. Soy protein did have approval for use as a binder in cardboard boxes and this approval was allowed to continue because researchers considered that migration of nitrites from the box into the food contents would be too small to constitute a cancer risk. FDA officials called for safety specifications and monitoring procedures before granting of GRAS status for food. These were never performed. To this day, use of soy protein is codified as GRAS only for limited industrial use as a cardboard binder.

1979
Torum, B. Nutritional Quality of Soybean Protein Isolates: Studies in Children of Preschool Age. Soy Protein and Human Nutrition, Harold L Wilcke and others, eds, Academic Press, New York, 1979. A group of Central American children suffering from malnutrition was first stabilized and brought into better health by feeding them native foods, including meat and dairy products. Then for a two-week period these traditional foods were replaced by a drink made of soy protein isolate and sugar. All nitrogen taken in and all nitrogen excreted were measured. The researchers found that the children retained nitrogen and that their growth was “adequate,” so the experiment was declared a success. However, the researchers noted that the children vomited “occasionally,” usually after finishing a meal; over half suffered from periods of moderate diarrhea; some had upper respiratory infections; and others suffered from rash and fever. It should be noted that the researchers did not dare to use soy products to help children recover from malnutrition, and were obliged to supplement the soy? sugar mixture with nutrients largely absent in soy products, notably vitamins A, D, B12, iron, iodine and zinc.

1981
Casey CE and others. Availability of zinc: loading tests with human milk, cow’s milk, and infant formulas. Pediatrics 1981;68(3):394-6. Female subjects consumed 25 mg of zinc with milk or formula, the amount of which was calculated to provide 5 gm of protein, after an eight-hour fast. Blood samples were taken prior to (base line) and at 30-minute intervals for three hours after consumption of zinc. The plasma response with human milk was significantly greater than with cow’s milk and all the formulas. The response with cow’s milk and a cow’s milk-based formula was one third that with human milk; responses with a soy-based and two casein hydrolysate-based formulas were even lower.

1981
Lebenthal E and others. The development of pancreatic function in premature infants after milk-based and soy-based formulas. Pediatr Res 1981 Sep;15(9):1240-1244. Soy formula fed to premature babies caused in increase in digestive enzymes compared to milk-fed babies, indicating low digestibility of soy formula.

1982
Murphy PA. Phytoestrogen Content of Processed Soybean Foods. Food Technology. 1982:50-54. One hundred grams of soy protein, the maximum suggested cholesterol-lowering dose in the FDA-sanctioned health claim, can contain almost 600 mg of isoflavones.

1983
Wenk GL and Stemmer KL. Suboptimal dietary zinc intake increases aluminum accumulation into the rat brain. Brain Res 1983;288:393-395. Zinc deficiency will cause more aluminum to be absorbed into the body in general, and into the brain in particular. Aluminum will be absorbed by competing for binding sites on a zinc-containing ligand. Fluoride and phytates in soy formula will induce zinc deficiency.

1983
Poley JR and Klein AW. Scanning electron microscopy of soy protein-induced damage of small bowel mucosa in infants. J Pediatr Gastroenterol Nutr 1983 May;2(2):271-87. Soy feeding caused damage to small bowel mucosa in 2 infants. The damage was similar to that of celiac disease and consistent with a lectin-induced toxicity.

1983
Tait S and others. The availability of minerals in food, with particular reference to iron. Journal of Research in Society and Health, April 1983;103(2):74?77. When precipitated soy products like tofu are consumed with meat, the mineral blocking effects of the phytates are reduced. The Japanese traditionally eat a small amount of tofu or miso as part of a mineral rich fish broth, followed by a serving of meat or fish.

1983
Ross RK. Effect of in-utero exposure to diethylstilbesterol on age at onset of puberty and on post-pubertal hormone levels in boys,” Canadian Medical Association Journal 1983, May 15;128(10):1197-8. Male children exposed during gestation to diethylstilbesterol (DES), a synthetic estrogen that has effects on animals similar to those of phytoestrogens from soy, had testes smaller than normal on maturation.

1984
Ologhobo AD and others. Distribution of phosphorus and phytate in some Nigerian varieties of legumes and some effects of processing. Journal of Food Science. January/February 1984;49(1):199-201. The phytic acid in soy is highly resistant to normal phytate-reducing techniques, such as soaking or long, slow cooking.

1985
Rackis JJ and others. The USDA trypsin inhibitor study. I. Background, objectives and procedural details. Qualification of Plant Foods in Human Nutrition, 1985;35. Diets of soy protein isolate high in trypsin inhibitors caused depressed growth and enlargement and pathological conditions of the pancreas, including cancer, and enlarged thryoid glands in rats. Analyses for this study showed that trypsin inhibitor content of soy protein isolate can vary as much as fivefold. Even low-level-trypsin-inhibitor SPI feeding resulted in reduced weight gain compared to controls. Soy protein isolate and textured vegetable protein made from soy protein isolate are used extensively in school lunch programs, imitation foods, commercial baked goods, diet beverages, meal replacements and fast food products. They are heavily promoted in Third World countries and form the basis of many food giveaway programs.

1986
McGraw MD and others. Aluminum content in milk formulae and intravenous fluids used in infants. Lancet I:157 (1986). Carefully collected human breast milk contained 5 to 20 micrograms aluminum per liter; concentrations were 10 to 20 fold greater in most cow’s milk-based formulas and 100-fold greater in soy-based formulas.

1986
Fort P and others. Breast feeding and insulin-dependent diabetes mellitus in children. J Am Coll Nutr 1986;5(5):439-441. Twice as many soy-fed children developed diabetes as those in a control group that was breastfed or received milk-based formula. It was based on this study that the American Academy of Pediatrics took a position of opposition to the use of soy infant formula. This objection was later dropped after the AAP received substantial grants from the Infant Formula Council.

1986
Freni-Titulaer LW and others. Am J Dis Child 1986 Dec;140(12):1263-1267.Soy infant feeding was associated with higher rates of early development in girls, including breast development and pubic hair before the age of eights, sometimes before the age of three.

1987
Tudor RJ and others. Comparative Subacute Effects Of Dietary Raw Soya Flour On The Pancreas Of Three Species, The Marmoset, Mouse and Rat. Food Chem Toxic. 25 (10), 739-45. Ingestion of soy produced enlarged pancreases in mice and “pancreatic adenoma and carcinoma in the rat.”

1987

Dabeka RW and McKenzie AD. Lead, cadmium, and fluoride levels in market milk and infant formulas in Canada. J Assoc Off Anal Chem 1987;70(4):754-7 (1987). Soy based or milk-free formulas contained about 8-15 times more cadmium than milk-based formulas as well as high amounts of fluoride.

1987
Katz SH. Food and Biocultural Evolution: A Model for the Investigation of Modern Nutritional Problems. Nutritional Anthropology, Alan R. Liss Inc., 1987, p 50. During the Chou Dynasty (1134 – 246 BC) the soybean was designated one of the five sacred grains, along with barley, wheat, millet and rice. However, the pictograph for the soybean, which dates from earlier times, indicates that it was not first used as a food; for whereas the pictographs for the other four grains show the seed and stem structure of the plant, the pictograph for the soybean emphasizes the root structure. Agricultural literature of the period speaks frequently of the soybean and its use in crop rotation. Apparently the soy plant was initially used as a method of fixing nitrogen. The soybean did not serve as a food until the discovery of fermentation techniques, sometime during the Chou Dynasty. Katz speculates that the rise of liver cancer in Africa is caused by the introduction of soy foods into the African diet.

1989
El Tiney A. Proximate Composition and Mineral and Phytate Contents of Legumes Grown in Sudan. Journal of Food Composition and Analysis 1989;2:67-68. Soybeans are listed as having some of the highest levels of phytic acid of all legumes. Phytic acid blocks the absorption of zinc, iron, copper and magnesium.

1990
Campbell TC. The Cornell-China-Oxford Project on Nutrition, Health and Environment. 1990; Chen J and others. Diet, Lifestyle and Mortality in China. A study of the characteristics of 65 counties. Monograph, joint publication of Oxford University Press, Cornell University Press, China People’s Medical Publishing House. 1990. This exhaustive study of Chinese diets found that legume consumption ranged from 0 to 58 grams per day, with an average of 13 grams. Assuming that two-thirds of this is from soybeans, then consumption averages about 9 grams of soy products per day. Isoflavone content would probably be about 10 mg/day.

1990
Fort P and others. Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. J Am Coll Nutr 1990;9:164-167. This study documents the association of soy formula feeding in infancy with autoimmune thyroid problems.

1990
Dabeka RW and McKenzie AD. Aluminium levels in Canadian infant formulate and estimation of aluminium intakes from formulae by infants 0-3 months old. Food Addit Contam 1990;7(2):275-82. Researchers found that aluminum content in soy formula for 1-3 month old infants could result in an intake of 363 micrograms/kg/day (2088 micrograms/day) alone, not including potential contribution from other foods or water.

1991
Hagger C and Bachevalier J. Visual habit formation in 3-month-old monkeys (Macaca mulatta): reversal of sex difference following neonatal manipulations of androgen. Behavior and Brain Research 1991, 45:57-63. Male infants undergo a “testosterone surge” during the first few months of life, when testosterone levels may be as high as those of an adult male. During this period, the infant is programmed to express male characteristics after puberty, not only in the development of his sexual organs and other masculine physical traits, but also in setting patterns in the brain characteristic of male behavior. In monkeys, deficiency of male hormones impairs the development of spatial perception (which, in humans, is normally more acute in men than in women), of learning ability and of visual discrimination tasks (such as would be required for reading.)

1993
Grant G and others. Pancreatic enlargement is evident in rats fed diets containing raw soybeans (Glycine max) or cowpeas (Vigna unguiculata) for 800 days but not in those fed diets based on kidney beans (Phaseolus vulgaris) or lupin seed (Lupinus angustifolius). J Nutr, 123(12), 2207-15. During the initial 150 days of the study, rats fed the soybean diet experienced abnormal levels pancreatic growth. Some of the rats fed the soybean diet also experienced the growth of nodules on the pancreas after 500 days.

1994
Messina MJ and others. Soy Intake and Cancer Risk: A Review of the In Vitro and In Vivo Data,” Nutrition and Cancer, 1994, 21:(2):113-131. This study fueled speculation on soy’s anti-carcinogenic properties. The authors noted that in 26 animal studies, 65 percent reported protective effects from soy. At least one study was left out, in which soy feeding caused pancreatic cancer, the 1985 study by Rackis. In the human studies listed, the results were mixed. A few showed some protective effect but most showed no correlation at all between soy consumption and cancer rates. “. . the data in this review cannot be used as a basis for claiming that soy intake decreases cancer risk.” In a subsequent book, The Simple Soybean and Your Health, Messina recommends 1 cup or 230 grams of soy products per day in his “optimal” diet as a way to prevent cancer.

1994
Hawkins NM and others. Potential aluminium toxicity in infants fed special infant formula. J Pediatr Gastroenterol Nutr 1994;19(4):377-81 (1994). Researchers found aluminum concentrations of 534 micrograms/L in soy formula, as compared to 9.2 micrograms/L in breast milk. The authors concluded that infants might be at risk from aluminium toxicity when consuming formula containing more than 300 micrograms/L.
1995
Chorazy PA and others. Persistent hypothyroidism in an infant receiving a soy formula: case report and review of the literature. Pediatrics 1995 Jul;96(1 Pt 1):148-50. The study describes a case of persistent hypothyroidism in an infant who had received soy formula.

1995
Anderson JW and others. Meta-analysis of the Effects of Soy Protein Intake on Serum Lipids. New England Journal of Medicine, 1995 333:(5):276-82. The FDA’s allowance of a health claim for soy protein is based largely on this meta-analysis, sponsored by Protein Technologies International. However, the study authors discarded eight studies for various reasons, leaving a remainder of 29. The published report suggested that individuals with cholesterol levels over 250 mg/dl would experience a “significant” reduction of 7 to 20 percent in levels of serum cholesterol if they substituted soy protein for animal protein. Cholesterol reduction was insignificant for individuals whose cholesterol was lower than 250 mg/dl. In other words, for most of the population, the substitution of meat with soy will not bring blood cholesterol levels down.

1996
Harras A, ed. Cancer Rates and Risks, 4th Edition, 1996, National Institutes of Health, National Cancer Institute. This report shows that the Japanese, and Asians in general, have lower rates of breast and prostate cancer but much higher rates of other types of cancer, particularly cancer of the esophagus, stomach, pancreas and liver.

1996
Fukutake M and others. Quantification of genistein and genistin in soybeans and soybean products. Food Chem Toxicol 1996;34:457-461. Average Isoflavones consumption in Japan was found to be about 10 mg per day.

1997
IEH assessment on Phytoestrogens in the Human Diet, Final Report to the Ministry of Agriculture, Fisheries and Food, UK, November 1997. This exhaustive report on phytoestrogens, prepared by the British government, failed to find much evidence of benefit and warned against potential adverse effects.

1997
Herman-Giddens ME and others. Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice: A Study from the Pediatric Research in Office Settings Network. Pediatrics, 1997 Apr;99:(4):505-512. Investigators found that one percent of all girls now show signs of puberty, such as breast development or pubic hair, before the age of three; by age eight, 14.7 percent of white girls and almost 50 percent of African-American girls had one or both of these characteristics. Our Comment: The widespread use of soy-based formula, beginning in the 1970s, is a likely explanation for the increase in early maturation in girls.

1998
Nagata C and others. Decreased serum total cholesterol concentration is associated with high intake of soy products in Japanese men and women. J Nutr 1998 Feb;128(2):209-13. This study included a survey of soy consumption among Japanese men and women. Consumption of soy products was about 54 grams per day for women and 64 grams per day for men. The total amount of soy protein from these products was 7-8 grams providing about 25 mg Isoflavones.

1998
Irvine CH and others. Phytoestrogens in soy-based infant foods: concentrations, daily intake and possible biological effects. Proc Soc Exp Biol Med 1998 Mar;217(3):247-53. Researchers found that soy formulas provide infants with a daily dose rate of 3 mg/kg body weight total isoflavones, “which is maintained at a fairly constant level between 0-4 months of age. . . . This rate of isoflavone intake is much greater than that shown in adult humans to alter reproductive hormones.”

1998
Yaffe K and others. Serum estrogen levels, cognitive performance, and risk of cognitive decline in older community women. J Am Geriatr Soc 1998 Jul;46(7):918-20. Women in the higher estrone quartiles had lower performance on two cognitive tests.

1998
Irvine CH and others. Daily intake and urinary excretion of genistein and daidzein by infants fed soy- or dairy-based infant formulas. Am J Clin Nutr 1998 Dec;68(6 Suppl):1462S-1465S. Researchers found that “young infants are able to digest, absorb, and excrete genistein and daidzein from soy-based formulas as efficiently as do adults consuming soy products.

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 (B Aires) 1999;59:747-752. Rats fed soy-based chow had reduced growth and an increase in gastrointestinal problems compared to controls.

1999
Nilhausen K 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
Food Labeling: Health Claims: Soy Protein and Coronary Heart Disease, Food and Drug Administration 21 CFR Part 101 (Docket No. 98P-0683). This US government document allows a health claim for foods containing 6.25 grams of soy protein per serving. The original petition, submitted by Protein Technologies International (a division of Dupont), requested a health claim for isoflavones, the estrogen-like compounds found plentifully in soybeans, based on assertions that “only soy protein that has been processed in a manner in which isoflavones are retained will result in cholesterol-lowering.” In 1998, the FDA made the unprecedented move of rewriting PTI’s petition, removing any reference to the phytoestrogens and substituting a claim for soy protein, a move that was in direct contradiction to the agency’s regulations. The FDA is authorized to make rulings only on substances presented by petition. The abrupt change in direction was no doubt due to the fact that a number of researchers, including scientists employed by the US government, submitted documents indicating that isoflavones are toxic. The regulations stipulate that 25 grams of soy protein per day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. Twenty-five grams soy protein can contain from 24-125 mg isoflavones, depending on processing methods. Many letters were written in protest, expressing concerns about mineral blocking effects, enzyme inhibitors, goitrogenicity, endocrine disruption, reproductive problems and increased allergic reactions from consumption of soy products.

1999
Sheehan DM and Doerge DR, Letter to Dockets Management Branch (HFA-305) February 18, 1999. A strong letter of protest from two government researchers at the National Center for Toxicological Research urging that soy protein carry a warning label rather than a health claim.

1999
Ginsburg J and Prelevic GM. Is there a proven place for phytoestrogens in the menopause?” Climacteric, 1999;2:75-78. Quantification of discomfort from hot flashes is extremely subjective and most studies show that control subjects report reduction in discomfort in amounts equal to subjects given soy.

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
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
Vincent A and Fitzpatrick LA. Soy isoflavones: are they useful in menopause? Mayo Clin Proc 2000;75:1174-84. “Current data are insufficient to draw definitive conclusions regarding the use of isoflavones as an alternative to estrogen for hormone replacement in postmenopausal women.”

2000
North K and Golding J. A maternal vegetarian diet in pregnancy is associated with hypospadias. The ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood. BJU Int 2000 Jan;85(1):107-113. Vegetarian women are more likely consume more soy than the general population. Incidence of hypospadias was twice as great in vegetarian mothers than in non-vegetarian mothers. Hypospadias is a birth defect due to interrupted development of the penis.

2000
Nakamura Y and others. Determination of the levels of isoflavonoids in soybeans and soy-derived foods and estimation of isoflavonoids in the Japanese daily intake. J AOAC Int 2000;83:635-650. This survey found that average isoflavone consumption in Japan is about 28 mg per day.

2000
Bee G. Dietary Conjugated Linoleic Acids Alter Adipose Tissue and Milk Lipids of Pregnant and Lactating Sows. J Nutr 2000;130:2292-2298. Dietary mixtures for pigs, which are carefully formulated to promote reproduction and growth, allow approximately 1 percent of the ration as soy in a diet based on grains and supplements. (Pigs have a digestive system similar to humans.) The Central Soya Company, Inc. website gives a range of 2.5 percent to 17.5 percent soy in the diet of pigs, citing a number of anti-nutritional components that “have been documented to cause gastrointestinal disturbance, intestinal damage, increased disease susceptibility and reduced performance in pigs.”

2000
Nagata C. Ecological study of the association between soy product intake and mortality from cancer and heart disease in Japan. International Journal of Epidemiology Oct 2000; 29(5):832-6. This study contained the following official conclusion: “The present study provides modest support for the preventive role of soy against stomach cancer and heart disease death.” However, only the association with lower heart disease death is correct. What the study actually found was that “Soy protein intake was significantly correlated with stomach cancer mortality rate in men” and “soy product intake estimated as total amount as well as isoflavone and soy protein intake were significantly positively correlated with colorectal cancer mortality rates in both sexes.” In other words, men who consumed lots of soy had more stomach cancer and men and women who consumed lots of soy had more colorectal cancer. These results are especially interesting as soy proponents often claim that Asians have lower rates of colorectal cancer because they eat more soy.

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. J Agric Food Chem 2001 Sep;49(9):4262-6. Soy foods were found to be high in oxalates and likely to contribute to kidney stones.

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 IFG-I are also found in rBGH milk and have been implicated in causing hormonal cancers.

2002
Sun CL and others. Dietary soy and increased risk of bladder cancer: the Singapore Chinese Health Study. Cancer Epidemiol Biomarkers Prev. 2002 Dec;11(12):1674-7. People who consumed 92.5 grams of soy per 1000 Kcal were found to be 2.3 times more likely to be at risk for bladder cancer. The results were calculated to factor in levels of education and cigarette consumption in study participants.

2003
Lack G and others. Factors associates with the development of peanut allergy in childhood. N Engl J Med 2003 Mar 13;348(11):977-85. The number of children with life-threatening peanut allergies has tripled during the last decade. This study suggests a link between consumption of soy-based formula and the development of peanut allergies. Scientists at the University of Bristol monitored 14,000 babies in the southwest of England. Among the 49 children who developed a peanut allergy, almost a quarter had consumed soy milk during their first two years. (Less than 5 percent of babies overall receive soy formula in the UK.) According to lead researcher Gideon Lack, “These results suggest that sensitization to peanut may possibly occur. . . as a result of soya exposure.”

2004
Conrad S and others. Soy formula complicates management of congenital hypothyroidism. Archives of Disease in Childhood 2004 Jan;89(1):37-40. Soy formula was found to increase the level of thyroid stimulating hormones in infants.

2008
Hogervorst E and others. High Tofu Intake Is Associated with Worse Memory in Elderly Indonesian Men and Women. Dementia and Geriatric Cognitive Disorders 2008;26(1):50-7. The study found that those who ate tofu regularly had worse memory than those who did not. The study also found that tempe consumption increased memory, possibly due to its high levels of folate caused by fermentation.

2008
Banta JP and others. Whole soybean supplementation and cow age class: Effects on intake digestion, performance and reproduction of beef cows. J Anim Sci 2008.86: 1868-78. Experiments conducted found that whole soybean supplement caused increased luteal activity in mature cows at the start of the breeding season . In 2 year old cows it caused less luteal activity than normal.

2010

Menopause. 2010 May-Jun;17(3):587-93. doi: 10.1097/gme.0b013e3181cb85d3.
One-year soy protein supplementation does not improve lipid profile in postmenopausal women.
Campbell SC1, Khalil DA, Payton ME, Arjmandi BH.

Our data indicate that 1-year soy protein supplementation did not confer cardi-ovascular benefits, in terms of favorable alterations in the lipid profile, in this cohort of postmenopausal women. These findings, as well as those from other studies, lend credence to the decision of the Food and Drug Administration to reevaluate the soy protein health claim issued a decade ago.

 2014

J Nutr. 2014 Jun;144(6):921-8. doi: 10.3945/jn.114.190454. Epub 2014 Apr 3.
Dietary soy intake is not associated with risk of cardiovascu-lar disease mortality in Singapore Chinese adults.
Talaei M1, Koh WP2, van Dam RM3, Yuan JM4, Pan A5.Concluded
“In conclusion, soy intake was not significantly associated with risk of cardiovascular disease mortality in the Chinese population. However, a slightly increased risk asso-ciated with high soy protein intake in men cannot be excluded and requires further in-vestigation.

 2014
Rev Bras Ginecol Obstet. 2014 Jun;36(6):251-8.
The effect of soy dietary supplement and low dose of hor-mone therapy on main cardiovascular health biomarkers: a randomized controlled trial.
Carmignani LO, Pedro AO, da Costa-Paiva LH, Pinto-Neto AM.

The use of dietary soy supplement did not show any significant favorable effect on cardiovascular health biomarkers compared with HT (low dose hormone therapy).

Jill Nienhiser has been a Weston A. Price Foundation member since 2001, and has provided web maintenance, editing, and proofreading support for westonaprice.org and realmilk.com for many years. She also helped launched the Farm-to-Consumer Legal Defense Fund in 2007.

2 Responses to Studies Showing Adverse Effects of Dietary Soy, 1939-2014

  1. James says:

    Past few days I started to eat red cowpea. Feeling an odd pain on the right mech closer to right jaw. A week ago I got the same feeling. I ate about 1/2 a tea mug. Anything to do with thyroid. Daily I take 100 mcg thyroxine tab. I never had such feeling earlier. I pressure cooked 250 grms. Something tells me that I must stop eating. Can you please help me to know. I have heard of Soya and bad for thyroid. Is it the same with cowpea. Greatly appreciate your reply please. I am over 60. I am 6 days a week vegetarian past two years. Eat little or fish once a week. Do not eat process ed foods, soft drinks, cordial etc. No smoking or liquor.

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