Monday, March 17, 2008

Soy Truths and Mistruths

Myths and Truths About Soy

Starting Out

While I have already posted on this topic, I am going to do a more in-depth blog on this matter that will always stay at the top of the other blogs that I will post here. Mind you I do not post much at this site in general (as my interests ultimately lie elsewhere), but this topic is one that I believe needs more reflection by those persons who feel that Soy is “the way to either replace proteins, vitamin B12, or simply ad to a “healthy” diet.


One of the first myths is that the Asian world eats a lot of it. The truth of the matter s quite different than others would have us believe. The average consumption of soy foods in Japan and China is 10 grams (about 2 teaspoons) per day. Asians consume soy foods in small amounts as a condiment, and not as a replacement for animal foods.

This is a refutation of what I am constantly told by many – at my work – that al we need to do is look to the Asian culture for evidence of health verses quantity of intake. Another myth that bugs me is the myth that soy products, even fermented soy products (which are superior to regular soy more common to large production quantities), provide a good source for vitamin B12 in vegetarian/vegan diets. The truth of the matter is that the compound that resembles vitamin B12 in soy cannot be used by the human body; in fact, soy foods cause the body to require more B12.

Why do I delineate between fermented soy and modern production methods which differ from the ancient ways of producing soy enriched products? Because fermentation neutralizes toxins in soybeans, and are processed in a way that denatures proteins and increases levels of carcinogens. Denatured is defined as used here as:

  • to cause the tertiary structure of a protein to unfold, as with heat, alkali, or acid, so that some of its original properties, especially its biological activity, are diminished or eliminated.

This is what effectively isn’t being done in most of today’s modern soy products, speaking here of many of the tofu’s and soy milks as well as the many other products.

Tempe, Miso and Nato would be a better choice for soy intake as they are fermented, see the video below for a better explanation than I can give:

Greedy Corporate Soy Producers!

From soy milk, tofu, and textured protein to mayonnaise, bakery products, margarine, and ice cream, soy products may be found in most processed foods in the supermarket and fast food chains, inflicting hormonal imbalances which may lead to cancer, osteoporosis, obesity, heart disease, sexual development abnormalities, learning disabilities, immune deficiencies, and infertility. The US Government sends soy products to foreign lands to mitigate hunger and malnutrition and thus causes even greater malnutrition, despite nearly half a century of research warning of the dangers of soy products.

"The industry has known for years that soy contains many toxins. At first they told the public that the toxins were removed by processing. When it became apparent that processing could not get rid of them, they claimed that these substances were beneficial. Your government granted a health claim to a substance that is poisonous, and the industry lied to the public to sell more soy." Sally Fallon, Nourishing Traditions: The Cookbook that Challenges Politically Correct Nutrition and the Diet Dictocrats (1999, 2nd edition, New Trends Publishing)

The Fairy Tale of Soy

This is another thing that baffles me. Most of the people that follow these diets tend to be liberal, and many of these liberal person’s have a “conspiratorial eye” towards corporations and their greed factor as well as the government aspect, specifically government “funded” by corporations. These people generally do not trust all the products these corporations push, but they say this while not connecting the fact that the soy industry is a huge multi-billion-dollar making conglomerate of corporately owned money making people that will not allow negative news about their products to reach the common man. Now obviously I do not adhere to these conspiracy theories as do my more left-leaning counterparts. But for them to believe that only products they don’t use are guided by corporate entities is, well, an uneducated supposition. I hear about who funded which study in regards to countering anthropogenic global warming, but this same criteria is not applied to their own “golden calves.”

"Each year, research on the health effects of soy and soybean components seems to increase exponentially. Furthermore, research is not just expanding in the primary areas under investigation, such as cancer, heart disease and osteoporosis; new findings suggest that soy has potential benefits that may be more extensive than previously thought."

So writes Mark Messina, PhD, General Chairperson of the Third International Soy Symposium, held in Washington, DC, in November 1999.1 For four days, well-funded scientists gathered in Washington made presentations to an admiring press and to their sponsors - United Soybean Board, American Soybean Association, Monsanto, Protein Technologies International, Central Soya, Cargill Foods, Personal Products Company, SoyLife, Whitehall-Robins Healthcare and the soybean councils of Illinois, Indiana, Kentucky, Michigan, Minnesota, Nebraska, Ohio and South Dakota.

The symposium marked the apogee of a decade-long marketing campaign to gain consumer acceptance of tofu, soy milk, soy ice cream, soy cheese, soy sausage and soy derivatives, particularly soy isoflavones like genistein and diadzen, the oestrogen-like compounds found in soybeans. It coincided with a US Food and Drug Administration (FDA) decision, announced on October 25, 1999, to allow a health claim for products "low in saturated fat and cholesterol" that contain 6.25 grams of soy protein per serving. Breakfast cereals, baked goods, convenience food, smoothie mixes and meat substitutes could now be sold with labels touting benefits to cardiovascular health, as long as these products contained one heaping teaspoon of soy protein per 100-gram serving.

The Fairy Tale of Soy

These industries and corporations have a lot of money invested in as well as to be made by selling their product. So these people are not un-biased in their “marketing of soy products. One customer asked what the problem with adding soy to diets would be, I will explain some of the adverse effects of it, as well as exploding a big myth about something I hear all the time, which is, blaming early puberty on anti-biotic and steroid infused Beef. I will argue that as more soy is added to products we will see earlier puberty in females and more erectile dysfunction (ED) in men. Not to mention an increase in obesity in children and adults.

Childhood Obesity, Early Puberty, Erectile Dysfunction

Estrogenic isoflavones, such as genistein and daidzein, are present in virtually all natural-ingredient rodent diets that use soy as a source of protein. Since these compounds are endocrine-active, it is important to determine whether the amounts present in rodent diets are sufficient to affect sexual development. The present study consisted of in vitro and in vivo parts. In the in vitro portion, human hepatoma cells were transfected with either rat estrogen receptor (ER) alpha or beta plus an estrogen-responsive luciferase reporter gene. Genistein and daidzein were complete agonists at both ERs, genistein being more potent than daidzein, and both compounds were more potent at ER beta than ER alpha. In combined studies with estradiol, genistein exerted additive effects with estradiol in vitro. In the in vivo portion of the study, groups of six pregnant Sprague-Dawley females were fed one of the following four diets, and the pups were maintained on the same diets until puberty: (1) a natural-ingredient, open-formula rodent diet (NIH-07) containing 16 mg genistein and 14 mg daidzein per 100 g of feed; (2) a soy- and alfalfa-free diet (SAFD) in which casein and corn oil were substituted for soy and alfalfa meal and soy oil, respectively, that contained no detectable isoflavones; (3) SAFD containing 0.02% genistein (GE.02); or (4) SAFD containing 0.1% genistein (GE.1). In the GE.1 group, effects of dietary genistein included a decreased rate of body-weight gain, a markedly increased (2.3-fold) uterine/body weight (U/BW) ratio on postnatal day (pnd) 21, a significant acceleration of puberty among females, and a marginal decrease in the ventral prostate weight on postnatal day (pnd) 56. However, developmental differences among the groups fed SAFD, GE.02, or NIH-07 were small and suggested minimal effects of phytoestrogens at normal dietary levels. In particular, on pnd 21, the U/BW ratio of the GE.02 and NIH-07 groups did not differ significantly from that of the SAFD group. Only one statistically significant difference was detected between groups fed SAFD and NIH-07: the anogenital distance (AGD) of female neonates on pnd 1 whose dams were fed NIH-07 was 12% larger than that of neonates whose dams were fed SAFD. The results suggest that normal amounts of phytoestrogens in natural-ingredient rodent diets may affect one developmental parameter, the female AGD, and that higher doses can affect several other parameters in both males and females. Based on these findings, we do not suggest replacing soy- and alfalfa-based rodent diets with phytoestrogen-free diets in most developmental toxicology studies. However, phytoestrogen-free diets are recommended for endocrine toxicology studies at low doses, to determine whether interactive effects may occur between dietary phytoestrogens and man-made chemicals.

“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 Oct;51(2):236-44, by Casanova M, You L, Gaido KW, Archibeque-Engle S, Janszen DB, Heck HA. Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina 27709, USA.

Found at:

Epidemiological evidence suggests that isoflavone phytoestrogens may reduce the risk of cancer, osteoporosis, and heart disease, effects at least partially mediated by estrogen receptors alpha and beta (ERalpha and ERbeta). Because isoflavone dietary supplements are becoming increasingly popular and are frequently advertised as natural alternatives to estrogen replacement therapy, we have examined the effects of one of these supplements on estrogen-dependent behavior and ERalpha- and ERbeta-dependent gene expression in the brain. In the adult female rat brain, 17beta-estradiol treatment decreased ERbeta messenger RNA signal in the paraventricular nucleus by 41%, but supplement treatment resulted in a 27% increase. The regulation of ERbeta in the paraventricular nucleus is probably via an ERbeta-dependent mechanism. Similarly, in the ventromedial nucleus of the hypothalamus, supplement treatment diminished the estrogen-dependent up-regulation of oxytocin receptor by 10.5%. The regulation of oxytocin receptor expression in the ventromedial nucleus of the hypothalamus is via an ERalpha-dependent mechanism. Supplement treatment also resulted in a significant decrease in receptive behavior in estrogen- and progesterone-primed females. The observed disruption of sexual receptivity by the isoflavone supplement is probably due to antiestrogenic effects observed in the brain. These results suggest that isoflavone phytoestrogens are antiestrogenic on both ERalpha- and ERbeta-dependent gene expression in the brain and estrogen-dependent behavior.

“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, by Patisaul HB, Dindo M, Whitten PL, Young LJ. Center for Behavioral Neuroscience, Emory University, Atlanta, Georgia 30329, USA.

Found at:

We report here the effects of oral micronized estradiol and soy phytoestrogens on uterine weight, choline acetyltransferase (ChAT) and nerve growth factor (NGF) mRNAs in the frontal cortex and hippocampus of ovariectomized young and retired breeder rats. Within each age category, 15 bilaterally ovariectomized rats were randomized equally into three groups: control (OVX), estradiol (E2), and soy phytoestrogens (SBE). The OVX rats were fed a casein/lactalbumin-based control diet; the E2 rats were fed with the control diet with added estradiol; and the SBE rats were fed with the control diet with added soy phytoestrogens. After 8 weeks of treatment, blood, uteri, frontal cortex, and hippocampus were collected at necropsy. Results showed that the uterine weights and serum estradiol concentrations were significantly higher in the E2 group compared with those in the OVX and SBE groups. In the hippocampus of young rats, E2 treatment resulted in significantly higher NGF mRNA levels than no treatment (OVX), and NGF mRNA levels in the SBE group were intermediate between the E2 and OVX groups. ChAT mRNA levels were significantly higher in the frontal cortex of E2 and SBE-treated retired breeder rats compared to OVX retired breeder rats. There were no differences among treatment groups for ChAT mRNA levels in the frontal cortex of young rats and in the hippocampus of both young and retired breeder rats. Our data suggest that soy phytoestrogens may function as estrogen agonists in regulating ChAT and NGF mRNAs in the brain of female rats.

“Effect of estradiol and soy phytoestrogens on choline acetyltransferase and nerve growth factor mRNAs in the frontal cortex and hippocampus of female rats,” Proc Soc Exp Biol Med 1999 Jun;221(2):118-25, by Pan Y, Anthony M, Clarkson TB. Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1040, USA.

Found at:

There are about 70 more such studies at Scientific Abstracts of Found at: Too many to list in fact.

Dangers of Soy

So what are the dangers involved with soy in your diet? Lets see:

  • High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.
  • Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic orders. In test animals soy containing trypsin inhibitors caused stunted growth.
  • Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.
  • Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimmune thyroid disease.
  • Vitamin B12 analogs in soy are not absorbed and actually increase the body’s requirement for B12.
  • Soy foods increase the body’s requirement for vitamin D.
  • Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein.
  • Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.
  • Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing and added to many soy foods.
  • Soy foods contain high levels of aluminum which is toxic to the nervous system and the kidneys.


  • Babies fed soy-based formula have 13,000 to 22,000 times more estrogen compounds in their blood than babies fed milk-based formula.
  • Infants exclusively fed soy formula receive the estrogenic equivalent of at least five birth control pills per day.
  • 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, baby boys are programmed to express male characteristics after puberty, not only in the development of their sexual organs and other masculine physical traits, but also in setting patterns in the brain characteristic of male behavior.
  • Pediatricians are noticing greater numbers of boys whose physical maturation is delayed, or does not occur at all, including lack of development of the sexual organs. Learning disabilities, especially in male children, have reached epidemic proportions.
  • Soy infant feeding—which floods the bloodstream with female hormones that inhibit testosterone—cannot be ignored as a possible cause for these tragic developments. In animals, soy feeding indicates that phytoestrogens in soy are powerful endocrine disrupters.
  • Almost 15 percent of white girls and 50 percent of African-American girls show signs of puberty such as breast development and pubic hair, before the age of eight. Some girls are showing sexual development before the age of three. Premature development of girls has been linked to the use of soy formula and exposure to environmental estrogens such as PCBs and DDE.

I have to go to work but will add to this blog in the near future.

Mothering Magazine article (imported article)

Whole Soy Story: The Dark Side of America's Favorite Health Food
By Kaayla T. Daniel
Issue 124: May/June 2004

Over the past decade, soy foods have become America's favorite health food. Newspapers, magazines, and best-selling health writers have proclaimed the "joy of soy" and promoted the belief that soy food is the key to disease prevention and maximum longevity.

The possibility that an inexpensive plant food could prevent heart disease, fight cancer, fan away hot flashes, and build strong bodies in far more than 12 ways is seductive. The truth, unfortunately, is far more complex. Soy foods come in a variety of forms, including many heavily processed modern products. Even good forms of soy foods must be eaten sparingly-the way they have been eaten traditionally in Asia. Most important, many respected scientists have issued warnings stating that the possible benefits of eating soy should be weighed against the proven risks. Indeed, thousands of studies link soy to malnutrition, digestive distress, immune-system breakdown, thyroid dysfunction, cognitive decline, reproductive disorders and infertility-even cancer and heart disease.

Americans rarely hear anything negative about soy. Thanks to the shrewd public relations campaigns waged by Archer Daniels Midland (ADM), Protein Technologies International (PTI), the American Soybean Association, and other soy interests, as well as the Food and Drug Administration's (FDA) 1999 approval of the health claim that soy protein lowers cholesterol, soy maintains a "healthy" image.

This article is written for parents who need to know the risks of feeding soy formula to infants, or soy milk and other soy foods to growing children. It's designed for prospective mothers and fathers who need to know the links between soy foods, infertility, and birth defects. Finally, it will serve anyone considering soy as a preventive for menopausal symptoms, osteoporosis, cancer, heart disease, or other ills.

How Much Soy Do Asians Really Eat?
Those who dare to question the benefits of soy tend to receive one stock answer: Soy foods couldn't possibly have a downside because Asians eat large quantities of soy every day and consequently remain free of most western diseases. In fact, the people of China, Japan, and other countries in Asia eat very little soy. The soy industry's own figures show that soy consumption in China, Indonesia, Korea, Japan, and Taiwan ranges from 9.3 to 36 grams per day.1 That's grams of soy food, not grams of soy protein alone. Compare this with a cup of tofu (252 grams) or soy milk (240 grams).2 Many Americans today think nothing of consuming a cup of tofu, a couple glasses of soy milk, handfuls of soy nuts, soy "energy bars," and veggie burgers. Infants on soy formula receive the most of all, both in quantity and in proportion to body weight.

In short, there is no historical precedent for eating the large amounts of soy food now being consumed by infants fed soy formula and vegetarians who favor soy as their main source of protein, or for the large amounts of soy being recommended by Dr. Andrew Weil, Dr. Christiane Northrup, and many other popular health experts.

What's more, the rural poor in China have never seen-let alone feasted on-soy sausages, chili made with Textured Vegetable Protein (TVP), tofu cheesecake, packaged soy milk, soy "energy bars," or other newfangled soy products that have infiltrated the American marketplace.

The Right Stuff
The ancient Chinese honored the soybean with the name "the yellow jewel" but used it as "green manure"-a cover crop plowed under to enrich the soil. Soy did not become human food until late in the Chou Dynasty (1134-246 B.C.), when the Chinese developed a fermentation process to make soybean paste, best known today by its Japanese name, miso.3 Soy sauce-the natural type sold under the Japanese name shoyu-began as the liquid poured off during the production of miso. Two other popular fermented soy foods, natto and tempeh, entered the food supply around 1000 A.D. or later in Japan and Indonesia, respectively.

Tofu came after miso. Legend has it that, in 164 B.C., Lord Liu An of Huai-nan, China-a renowned alchemist, meditator, and ruler-discovered that a purée of cooked soybeans could be precipitated with nigari (a form of magnesium chloride found in seawater) into solid cakes, called tofu. In Japan, as in China, tofu was rarely served as a main course anywhere except in monasteries. Its most popular use was-and is-as a few bland little blocks in miso soup or fish stock.

The Chinese almost never ate boiled or baked soybeans or cooked with soy flour except in times of famine. Modern soy products such as soy protein isolate (SPI), TVP, soy-protein concentrate, and other soy-protein products made using high-tech industrial processes, were unknown in Asia until after World War II.4

Contrary to popular belief, neither soy milk nor soy infant formula is traditional in Asia. Soy milk originated as a byproduct of the process of making tofu; the earliest reference to it as a beverage appeared in 1866.5 By the 1920s and 1930s, it was popular in Asia as an occasional drink served to the elderly.6-8 The first person to manufacture soy milk in China was actually an American-Harry Miller, a Seventh Day Adventist physician and missionary.9

The first soy infant formulas in China were developed in the 1930s and have never been widely used.10-14 Today, babies in Asia are almost always breastfed for at least the first six months, then switched to a dairy-based infant formula. Orphans and others who cannot be breastfed by a wet nurse are fed from birth on dairy formulas.15

Claims that soybeans have been a major part of the Asian diet for more than 3,000 years, or from "time immemorial," are simply not true.

Processing Matters
Soy in the West has been a product of the industrial revolution-an opportunity for technologists to develop cheap meat substitutes, to find clever new ways to hide soy in familiar food products, to formulate soy-based pharmaceuticals, and to develop a renewable, plant-based resource that could replace petroleum-based plastics and fuels.

For years, the soy protein left over from soy-oil extraction went to animals and poultry. Now that food scientists have discovered inexpensive ways to improve or disguise the color, flavor, "bite characteristics," and "mouth feel" of soy protein-based products, soy is being aggressively marketed as a "people feed." Although the newer refining techniques yield blander, purer soy proteins than the "beany," hard-to-cover-up flavors of the past, the main reason that soy foods now taste and look better is the lavish use of unhealthy additives such as sugar and other sweeteners, salt, artificial flavorings, colors, and monosodium glutamate (MSG).

Soy now lurks in nearly 60 percent of the foods sold in supermarkets and natural food stores. Much of this is "hidden" in products where it wouldn't ordinarily be expected, such as fast-food burgers and Bumblebee canned tuna. Soy is also a key ingredient in ersatz products with names like Soysage, Not Dogs, Fakin Bakin, Sham Ham, and TofuRella, which have been named after and made to look like the familiar meat and diary products they are intended to replace.

There's nothing natural about these modern soy protein products. Textured soy protein, for example, is made by forcing defatted soy flour through a machine called an extruder under conditions of such extreme heat and pressure that the very structure of the soy protein is changed. Production differs little from the extrusion technology used to produce starch-based packing materials, fiber-based industrial products, and plastic toy parts, bowls, and plates.16

The process of making soy protein isolate (SPI) begins with defatted soybean meal, which is mixed with a caustic alkaline solution to remove the fiber, then washed in an acid solution to precipitate out the protein. The protein curds are then dipped into another alkaline solution and spray-dried at extremely high temperatures. SPI is then often spun into protein fibers using technology borrowed from the textile industry. These refining processes remove "off flavors," "beany" tastes, and some of the worst flatulence-producing components. They improve digestibility, but vitamin, mineral, and protein quality are sacrificed, and levels of carcinogens such as nitrosamines are increased.17-22 SPIs appear in so many products that consumers would never guess that the Federation of American Societies for Experimental Biology (FASEB) decreed in 1979 that the only safe use for SPIs was for sealers for cardboard packages.23

Antinutrients and Toxins in Soy
Scientists who have studied the use of soy protein in animal feeds over the years have discovered a number of components in soy that cause poor growth, digestive distress, and other health problems.24-27 To list just a few of these: Protease inhibitors interfere with protein digestion and have caused malnutrition, poor growth, digestive distress, and pancreatitis.28 Phytates block mineral absorption, causing zinc, iron, and calcium deficiencies.29-34 Lectins and saponins have caused leaky gut and other gastrointestinal and immune problems.35-36 Oxalates-surprisingly high in soy-may cause problems for people prone to kidney stones and women suffering from vulvodynia, a painful condition marked by burning, stinging, and itching of the external genitalia.37, 38 Finally, oligosaccharides give soy its notorious reputation as a gas producer. Although these are present in all beans, soy is such a powerful "musical fruit" that the soy industry has identified "the flatulence factor" as a major obstacle that must be overcome for soy to achieve full consumer acceptance.39, 40

Apologists for soy dismiss such claims, saying that food processing and home cooking remove most of these antinutrients. In fact, modern processing removes most of them, but not all. The levels of heat and pressure needed to remove all protease inhibitors, for example, severely damage soy protein and make it harder to digest. The trick is to eliminate the most antinutrients while doing the least damage to the soy protein. Success varies widely from batch to batch.41-44

For years, the soy industry tried to improve the quality of animal feeds by finding better ways to get rid of these undesirable antinutrients. Having failed, they routinely supplement animal feeds heavily with vitamins, minerals, and methionine, a sulfur-containing amino acid that is low in soy. Even so, makers of animal chows are still limited in the amount of soy they can add without causing growth and fertility problems. Food processors making soy-protein products for people may or may not add these supplements. Generally, calcium and vitamin D are added to soy milk so it can compete with dairy products.

Today, the soy industry has switched tactics-from trying to remove unwanted antinutrients to trying to convince people that they are actually a good thing. Protease inhibitors, saponins, and lectins are being touted as curers of cancer or lowerers of cholesterol, while phytates are being recommended for their ability to remove toxic minerals such as cadmium and excess iron from the body.45-51 Although some of these uses look promising, it is important to note that researchers are not achieving these successes using regular soy foods. Most take carefully extracted components and administer them in carefully measured and monitored pharmaceutical doses. News headlines to the contrary, there is no reason to think that just eating a lot of soy foods will do the trick.

Soy Allergens
Soy is one of the top eight allergens that cause immediate hypersensitivity reactions such as coughing, sneezing, runny nose, hives, diarrhea, difficulty swallowing, and anaphylactic shock. Delayed allergic responses are even more common and occur anywhere from several hours to several days after the food is eaten. These have been linked to sleep disturbances, bedwetting, sinus and ear infections, crankiness, joint paint, chronic fatigue, gastrointestinal woes, and other mysterious symptoms.52, 53

Soy allergies are on the rise for three reasons: the growing use of soy infant formula (now 20 to 25 percent of the formula market), the increase in soy-containing foods in grocery stores, the possibility of the greater allergenicity of genetically modified soybeans.54 Although severe reactions to soy are rare compared to reactions to peanuts, tree nuts, fish, and shellfish, soy has been underestimated as a cause of food anaphylaxis. Recently, after a young girl in Sweden suffered an asthma attack and died after eating a hamburger that contained only 2.2 percent soy protein, Swedish researchers looked into a possible soybean connection. They concluded that the soy-in-the-hamburger case was not a fluke, and that minute amounts of soy "hidden" in regular food had caused four of the total of five deaths caused by allergic reactions in Sweden between 1993 and 1996. Of the children who suffered fatal attacks, all had been able to eat soy without any adverse reactions right up until the dinner that caused their deaths.55 According to the Swedish Ministry of Health and Social Affairs, children at highest risk are those who suffer from peanut allergies and asthma; parents of such children should make every effort to eliminate all soy from their children's diets.56

Soy and the Thyroid: A Pain in the Neck
More than 70 years of human, animal, and laboratory studies show that soybeans put the thyroid at risk. The chief culprits are the plant hormones in soy known as phytoestrogens or isoflavones.57-59 The United Kingdom's Committee on Toxicology has identified several populations at special risk: infants on soy formula, vegans who use soy as their principal meat and dairy replacements, and men and women who self-medicate with soy foods and/or isoflavone supplements in an attempt to prevent or reverse menopausal symptoms, cancer, or heart disease.60

Infants with congenital hypothyroidism need 18 to 25 percent higher doses of thyroxine drug than usual if they are bottle-fed with soy formula.61 Likewise, adults who boost their thyroid with drugs such as Synthroid while also eating thyroid-inhibiting foods such as soy put extreme stress on their thyroids. Toxicologist Michael Fitzpatrick, PhD, points out that this is the way that researchers induce thyroid cancers in laboratory animals.62

Soy and Reproduction: Breeding Discontent
Scientists have known since the mid-1940s that phytoestrogens can impair fertility. Fertility problems in cows, sheep, rabbits, cheetahs, guinea pigs, birds, and mice have all been reported.63, 64 Although scientists discovered only recently that soy lowers testosterone levels,65 tofu has traditionally been used in Buddhist monasteries to decrease the libido, and by Japanese women to punish straying husbands. Humans and animals appear to be the most vulnerable to the effects of soy estrogens prenatally, during infancy and puberty, during pregnancy and lactation, and during the hormonal shifts of menopause. Of all these groups, infants on soy formula are at the highest risk because of their small size and developmental phase, and because formula is their main source of nutrient.66, 67

A crucial time for the programming of the human reproduction system is right after birth-the very time when bottles of soy formula are given to many non-breastfed babies. Normally during this period, the body surges with natural estrogens, testosterones, and other hormones that are meant to program the baby's reproductive development from infancy through puberty and into adulthood. For infants on soy formula, this programming may be interrupted.68-70

Male infants experience a testosterone surge during the first few months of life and produce androgens in amounts equal to those of adult men. So much testosterone at such a tender age is needed to program the body for puberty, the time when a male's sex organs should develop and he should begin to express male characteristics such as facial and pubic hair and a deep voice. If receptor sites intended for the hormone testosterone are occupied by soy estrogens, however, appropriate development may never take place.71-74 To date, most of the evidence damning soy formula can be found only in animal studies, because investigations in which humans' sex hormone levels are lowered experimentally cannot ethically be done. However, in the years since soy formula has been in the marketplace, parents and pediatricians have reported growing numbers of boys whose physical maturation is either delayed or does not occur at all. Breasts, underdeveloped gonads, undescended testicles (cryptorchidism), and steroid insufficiencies are increasingly common. Sperm counts are also falling.75-79

Soy formula is bad news for girls as well. Natural estrogen levels approximately double during the first month of life, then decline and remain at low levels until puberty. With increased estrogens in the environment in the diet, an alarming number of girls are entering puberty much earlier than normal.80-82 One percent of girls now show signs of puberty, such as breast development or pubic hair, before the age of three. By the age of eight, 14.7 percent of Caucasian girls and 48.3 percent of African American girls had one or both of these characteristics.83 The fact that blacks experience earlier puberties than whites is not a racial difference but a recent phenomenon.84, 85

Most experts blame this epidemic of "precocious puberty" on environmental estrogens from plastics, pesticides, commercial meats, etc., but some pediatric endocrinologists believe that soy is a contributor.86 Of all the estrogens found in the environment, soy is the likeliest explanation of why African American girls reach puberty so quickly. Since its establishment in 1974, the federal government's Women, Infants and Children (WIC) program has provided free infant formula to teenage and other low-income mothers while failing to encourage breastfeeding. Because of perceived or real lactose intolerance, black babies are much more likely to receive soy formula than Caucasian babies.

Early maturation in girls heralds reproductive problems later in life, including amenorrhea (failure to menstruate), anovulatory cycles (cycles in which no egg is released), impaired follicular development (follicles failing to mature and develop into healthy eggs), erratic hormonal surges, and other problems associated with infertility. Because the mammary glands depend on estrogen for their development and functioning, the presence of soy estrogens at a susceptible time might predispose girls to breast cancer, another condition that is on the rise and definitively linked to early puberty.87

Recently, a team of researchers headed by Brian L. Strom, MD, studied the use of soy formula and its long-term impact on reproductive health. They announced only one adverse finding: longer, more painful menstrual periods among women who'd been fed soy formula in infancy.88 Dr. Strom's conclusion that the results were "reassuring" made newspaper headlines all over the world, though the data in the body of the report were anything but. Indeed, data left out of the headlines and buried in the report revealed higher incidences of allergies and asthma, and higher rates of cervical cancer, polycystic ovarian syndrome, blocked fallopian tubes, and pelvic inflammatory disease.89 Although thyroid damage from soy formula has been the principal concern of critics for decades, the researchers excluded thyroid function as a subject for study. Not surprisingly, this study was funded in part by the infant-formula industry.

Most of the fears concerning soy formula have focused on estrogens. There are other problems as well, notably much higher levels of aluminum, fluoride, and manganese than are found in either breastmilk or dairy formulas.90-96 All three metals have the potential to adversely affect brain development. Although trace amounts of manganese are vital to the development of the brain, toxic levels accrued from ingestion of soy formula during infancy have been found in children suffering from attention-deficit disorders, dyslexia, and other learning problems.97, 98

Soy apologists sometimes argue that the plant hormones in soy formula could not possibly be harmful because Japanese women eat a lot of soy products and so must have high levels of phytoestrogens in their breastmilk. Researchers, however, have measured the soy isoflavones in breastmilk and found them low even in vegetarian women who consume copious quantities of tofu, soy milk, soy protein shakes, and other soy foods.99-101

Limited evidence, however, suggests that vegetarian women who eat a lot of soy foods during pregnancy may put their infants at risk in terms of their future reproductive health, fertility, and possibly increased risk of breast cancer. All of the problems that have befallen infants on soy formula, as well as estrogen-related birth defects, have occurred (in animal studies, at least) to the offspring of mothers who were given high doses of soy during pregnancy.102 One of these birth defects that has been linked to vegetarian diets in humans is hypospadias, a developmental disorder in which the opening of the penis is located on the underside of the shaft.103

Until soy estrogens are definitely linked to reproductive-tract abnormalities, infertility, and other health problems in humans, most health authorities recommend that we "wait and see." This could be a terrible mistake.

In the 1940s and 1950s, another estrogen, diethylstilbestrol (DES), was widely given to Western women early in their pregnancies in a misguided attempt to prevent miscarriage. That fact is relevant not only because DES bears a striking structural similarity to some plant estrogens-including soy isoflavones-but because it took more than 20 years before the full spectrum of harmful effects was observed.104, 105

DES is 100,000 times more potent than soy phytoestrogens. However, the large quantities of phytoestrogens in soy products are more than enough to counteract their lower potency. When the effects of isoflavones in fetal and neonatal animals have been studied, they have paralleled those observed in human infants exposed to DES.106, 107 Recent studies indicate that the soy isoflavone known as genistein may be even more carcinogenic than DES.108

Yet the belief persists that soy hormones are "safe" because they are "weak" and "natural." Although the soy industry has claimed that soy estrogens are anywhere from 10,000 to 1,000,000 times weaker than the human estrogen estradiol, the correct figure is only 1,200 times as weak.109 Though this still sounds quite weak, it is not-because of the quantity of these estrogens ingested by infants on soy formula, and by children and adults who eat soy every day. These individuals consume far more soy estrogens than were ever part of a traditional diet in Asia. The average isoflavones intake in China is 3 milligrams, or 0.05 mg per kilogram of body weight. In Japan, the figures range from 10 to 28 mg, or 0.17 to 0.47 isoflavones per kg of body weight. In contrast, infants receiving soy formula average 38 mg of isoflavones, which comes to a shocking 6.25 mg/kg of body weight. Compare that dose to the 0.47 mg/kg per day fed to healthy Japanese adult men and women who experienced thyroid suppression after just three months-or to the 0.75 mg/kg of isoflavones fed to American women who experienced hormonal changes sufficient to skew their menstrual cycles after just one month.110 Although children and teenagers are less vulnerable than infants, their young bodies are still developing, and highly vulnerable to endocrine-system disruption by soy. And soy has been shown to pass through the placentas of pregnant women to their unborn babies.

Meanwhile, the jury is still out on whether soy might help alleviate menopausal symptoms or prevent osteoporosis and breast cancer. The soy industry's top scientists, convened at the Fifth International Symposium on the Role of Soy in the Preventing and Reversing Chronic Disease (held in Orlando, Florida, September 21-24, 2003), conceded that the data are confusing and contradictory, with some studies suggesting that soy might be helpful, and others showing that soy contributes to osteoporosis and promotes breast cancer.

What's certain is that the levels of soy estrogens that might possibly have a beneficial effect on hormonally related diseases have been proven to jeopardize the health of the thyroid. Likewise, the 25 grams of soy protein per day touted by the FDA to lower cholesterol (see sidebar, "Boon to the Industry: The FDA's Soy Protein Health Claim") is very likely to harm the thyroid, and thus increase one of the risk factors for heart disease.

The bottom line is that the safety of soy foods has yet to be proven, and that human beings have become guinea pigs in what Daniel M. Sheehan, formerly senior toxicologist with the FDA's National Center for Toxicological Research, has called a "large, uncontrolled and basically unmonitored human experiment."111

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3. Information about soy and agriculture can be found in Nutritional Anthropology (Liss, 1987) edited by Francis Johnston. For the history of miso, soy sauce, tempeh, tofu and other products see William Shurtleff and Akiko Aoyagi's The Book of Miso (Ten Speed Press, 1976) The Book of Tofu (Ballentine, 1979) and The Book of Tempeh (Ten Speed Press, 1979). Information about the history of soy, including modern manufacturing processes can be found in KeShun Liu's Soybeans: Chemistry, Technology and Utilization (Aspen, 1999).
4. William Shurtleff, Akiko Aoyagi, "The History of Soybean Crushing: Soy Oil and Soybean Meal," in The History of Soybeans and Soyfoods: Past, Present and Future (unpublished manuscript). Soyfoods Center, Lafayette, CA.
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38. Clive Solomon, "Low Oxalate Treatment," Click on "Treatments."
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40. A. Visser, A. Thomas, "Review: Soya Protein Products, Their Processing, Functionality and Application Aspects," Food Rev Inter 3, nos. 1 & 2 (1987): 1-32.
41. See Note 27.
42. See Note 28.
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44. P. C. Billings et al., "Protease Inhibitor Content of Human Dietary Samples," Nutr Cancer 14, no. 2 (1990): 85-93.
45. A. R. Kennedy, "The Bowman-Birk Inhibitor from Soybeans as an Anticarcinogenic Agent," Am J Clin Nutr 68, suppl. (1998): 1406S-1412S.
46. G. S. Sidhu, D. G. Oakenfull, "A Mechanism for the Hypocholesterolemic Activity of Saponins," Br J Nutr 7, no. 55 (1986): 643.
47. A. V. Rao, M. K. Sung, "Saponins as Anticarcinogens," J Nutr 125 (1995): 717S-724S.
48. R. Doyle, K. Keller, "Lectins in Diagnostic Microbiology," Eur J Clin Microbiol 3 (1983): 4-9.
49. A. M. Shamsuddin et al., "Novel Anti-Cancer Function of IP6: Growth Inhibition and Differentiation of Human Mammary Cancer Cell Lines in Vitro," Anticancer Res 16, no. 6A (1996): 3287-3292.
50. A. Baten et al., "Inositol-Phosphate Induced Enhancement of Natural Killer Cell Activity Correlates with Tumor Suppression," Carcinogenesis 10, no. 9 (1989): 1595-1598.
51. M. Jenab, L. U. Thompson, "Role of Phytic Acid in Cancer and Other Diseases," in Reddy, Sathe. See Note 29: 225-248.
52. "FAO Food Allergies Report of the Technical Consultation of the Food and Agricultural Organization of the United Nations, Rome" (13-14 November 1995).
53. J. Bousquet et al., "Scientific Criteria and Selection of Allergenic Foods for Labeling," Allergy 53, suppl. 47 (1998): 3-21.
54. Barbara Keeler, "A Nation of Lab Rats," Sierra Club Magazine (July/August 2001).
55. T. Foucard, I. Malmheden-Yman, "A Study on Severe Food Reactions in Sweden-Is Soy Protein an Underestimated Cause of Food Anaphylaxis," Allergy 53, no. 3 (1999): 261-265.
56. Letter from Ingrid Malmheden-Yman, PhD, Senior Chemist, Swedish National Food Administration, Livsmedels Verket to Ministry of Health in New Zealand (30 May 1997), released under Official Information Act.
57. M. Fitzpatrick, "Soy Formulas and the Effects of Isoflavones on the Thyroid," NZ Med J 113, no. 1103 (2000): 24-26.
58. D. R. Doerge, "Inhibition of Thyroid Peroxidase by Dietary Flavonoids," Chem Res Toxicol 9 (1996): 16-23.
59. R. L. Divi et al., Anti-Thyroid Isoflavones from Soybean," Biochem Pharmacol 54 (1997): 1087-1096.
60. Committee On Toxicology, British Food Standards Agencies (UK), Draft report of the COT Working Group on Phytoestrogens, "4:Sources and Concentrations of Phytoestrogens in Foods and Estimated Dietary Intake."
61. M. A. Jabbar et al., "Abnormal Thyroid Function Test in Infants with Congenital Hypothyroidism: The Influence of Soy-Based Formula," J Am Coll Nutr 16 (1997): 280-282.
62. See Note 57.
63. C. H. G. Irvine et al., "Phytoestrogens in Soy-Based Infant Foods: Concentrations, Daily Intake and Possible Biological Effects," Proc Soc Exp Biol Med 217 (1998): 247-253.
64. C. H. G. Irvine et al., "The Potential Adverse Effects of Soybean Phytoestrogens in Infant Feeding," NZ Med J 24 (1995): 318.
65. R. M. Sharpe et al., "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 Repro 17, no. 7 (2002): 1692-1703.
66. P. L. Whitten et al., "Potential Adverse Effects of Phytoestrogens," J Nutr 125 (1995): 771S-776S.
67. See Note 60: "5: Absorption, Distribution, Metabolism and Excretion of Phytoestrogens."
68. R. B. Clarkson et al., "Estrogen Soybean Isoflavones and Chronic Disease: Risks and Benefits," Trends, Endocrinol Metab 6 (1995): 11-16.
69. R. S. Kaldas, C. L. Hughes, "Reproductive and General Metabolic Effects of Phytoestrogens in Mammals," Repr Toxicol 3 (1989): 81-89.
70. See Note 63.
71. R. Santti R et al., "Phytoestrogens: Potential Endocrine Disrupters in Males," Toxicol Envir Health 14, nos. 1 & 2 (1998): 223-237.
72. L. S. Frawley, J. D. Neill, "Age-Related Changes in Serum Levels of Gonadotropins and Testosterone in Infantile Male Rhesus Monkeys," Biol Repro 20 (1979): 1147-1151.
73. D. R. Mann et al., "Blockade of Neonatal Activation of the Pituitary Testicular Axis: Effect on Peripubertal Lutenizing Hormone and Testosterone Secretion and on Testicular Development in Male Monkeys," J Clin Endocrinol Metab 68 (1989): 600-607.
74. J. S. D. Winter et al., "Pituitary-Gonadal Relations in Infancy: Patterns of Serum Gonadal Steroid Concentrations in Man from Birth to Two Years of Age," J Clin Endocrinol Metab 42 (1976): 679-686.
75. I. L. Sedimeyer, M. R. Palmert, "Delayed Puberty: Analysis of a Large Case Series from an Academic Center," J Clin Endocrinol Metab 87, no. 4 (2002): 1613-1620.
76. J. Hutson, M. Baker, "Hormonal Control of Testicular Descent and the Cause of Cryptorchidism," Repr Fert Dev 6 (1994): 151-156.
77. R. Sharpe, N. Shakkeback, "Are Oestrogens Involved in Falling Sperm Counts and Disorders of the Male Reproductive Tract?," Lancet 341 (1993): 1292-1395.
78. J. Auger et al., "Decline in Semen Quality Among Fertile Men in Paris During the Past 20 Years," NEJM 332, no. 5 (1995): 281-285.
79. Richard Sharpe, MD, as quoted by Aileen Ballantyne in "Why Our Men Are Getting Less Fertile," London Times (29 August 1995).
80. See Note 64.
81. See Note 74.
82. See Note 73.
83. Herman Giddens et al., "Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice," Pediatric Research in Office Settings Network 99, no. 4 (1997): 505-512.
84. Peter Montague, "The Obscenity of Accelerated Child Development," Ecologist 28, no. 3 (1993): 140-142.
85. L. Zacharias, R. J. Wurtman, "Age at Menarche," NEJM 280, no. 16 (1969): 868-875. This article includes results reported in N. Michaelson, "Studies in Physical Development of Negroes: IV. Onset of Puberty," Am J Phys Anthropol 2 (1944): 151-166.
86. C. L. Fenton, M. Poth, "Precocious Pseudopuberty," eMedicine 2, no. 5 (2001):
87. See Note 64.
88. B. L. Strom et al., "Exposure to Soy-Based Formula in Infancy and Endocrinological and Reproductive Outcomes in Young Adulthood," JAMA 286, no. 7 (2001): 897-814.
89. L. R. Goldman et al., "Exposure to Soy-Based Formula in Infancy," letter to the editor, JAMA 286, no. 19 (2001): 2402-2403.
90. M. Silva, E. C. Reynolds, "Fluoride Content of Infant Formulae in Australia," Austr Dent J 41, no. 1 (1996): 37-42.
91. S. J. Fomon, J. Ekstrand, "Fluoride Intake by Infants," J Public Health Dent 59, no. 4 (1999): 229-234.
92. R. Weintraub et al., "High Aluminum Content of Infant Milk Formulas." Arch Dis Child 61 (1986): 914-916.
93. W. W. K. Koo et al., "Aluminum Contamination of Infant Formulas," J Parenteral Enterol Nutr 12 (1988): 170-173.
94. N. M. Hawkins et al., "Potential Aluminum Toxicity in Infants Fed Special Infant Formula, J Pediatr Gastroenterol Nutr 19, no. 4 (1994): 377-381.
95. T. T. Tran et al., "Effect of High Dietary Manganese Intake of Neonatal Rats on Tissue Mineral Accumulation, Striatal Dopamine Levels and Neurodevelopmental Status," Neurotoxicol 23 (2002): 635-643.
96. T. T. Trans et al., "Effects of Neonatal Dietary Manganese Exposure on Brain Dopamine Levels and Neurocognitive Function," Neurotoxicol 23 (2002): 645-651.
97. D. Stasny et al., "Manganese Intake and Serum Manganese Concentration of Human Milk-Fed and Formula Fed Infants," Am J Clin Nutr 39, no. 6 (1984): 872-878.
98. P. J. Collipp et al., "Manganese in Infant Formulas and Learning Disability," Ann Nutr Metab 27 (1983): 488-494.
99. See Note 63.
100. A. A. Franke et al., "Daidzein and Genistein Concentrations in Human Milk After Soy Consumption," Clin Chem 42 (1996): 955-964.
101. K. D. R. Setchell et al., "Exposure of Infants to Phyto-Oestrogens from Soy-Based Infant Formula," Lancet 350, no. 9070 (1997): 23-27.
102. K. B. Declos et al., "Effects of Dietary Genistein Exposure During Development on Male and Female DC (Sprague-Dawley) Rats," Repro Toxicol 15, no. 6 (2001): 647-663.
103. K. North, J. Golding, ALSPAC Study Team, "A Maternal Vegetarian Diet in Pregnancy Is Associated with Hypospadias," BJU Inter 85 (2000): 107-113.
104. R. J. Apfel, S. M. Fischer, To Do No Harm: DES and the Dilemmas of Modern Medicine (New Haven, CT: Yale University Press, 1984).
105. K. D. R. Setchell, "Naturally Occurring Non-Steroidal Estrogens of Dietary Origin," in John A. McLachlan, ed., Estrogens in the Environment (New York: Elsevier, 1985).
106. E. M. Bickoff et al., "Relative Potencies of Several Estrogen-Like Compounds Found in Forages," Agri Food Chem 10 (1962): 410.
107. David J. Woodhams, "Nutritional Deficiencies in Soy Protein-based Infant Formulas," paper presented to the New Zealand Ministry of Health (5 March 1995).
108. R. R. Newbold et al., "Uterine Adenocarcinoma in Mice Treated Prenatally with Genistein," Cancer Res 61 (2001): 4325-4328.
109. L. Markiewicz et al., "In Vitro Bioassays of Non-Steroidal Phytoestrogens," J Steroids Biochem Mol Biol 45, no. 5 (1993): 399-405.
110. Sally Fallon, "Table: Phytoestrogens in Diets of Infants and Adults," Wise Traditions 2, no. 2 (Summer 2001): 53.
111. D. M. Sheehan, "Isoflavone Content of Breast Milk and Soy Formulas: Benefits and Risks," letter to the editor, Clin Chem 43 (1997): 850.

Dr. Jill Schneider - Lehigh University (imported article)

Answers to FAQs about Soy Isoflavones, Soy Infant Formula and Puberty

This is not my main field of research and expertise. The reason I am writing this is that I supervised a research project on the effects of genistein, a soy isoflavone, on puberty in hamsters (view a PDF of the power point presentation ). We presented this work at the Society for Neurosciences meeting in 2001. It received a great deal of press (far beyond the merits of the work), and I still receive emails every week from parents who want to know whether their child's precocious puberty might be due to having been fed soy infant formula. I don't know the answer to this question. I'm sorry to be of so little help. I hope something on this page might point you in the right direction.

Q: What are isoflavones?

A: Isoflavones are a class of chemical compounds. Genistein and daidzein are two isoflavones found in soy beans. These and other isoflavones are actually in many different kinds of legumes (beans), grains and vegetables.

The structure of the isoflavone molecule shares some critical similarities to estrogen, one of the hormones naturally produced in our own bodies (both male and female). Estrogen is, of course, produced in female ovaries and male testes, as well as in fat cells and certain brain cells. We also have special cells in our brains, reproductive organs , liver and fat cells that respond to estrogen, by virtue of the estrogen receptors in these cells.

Isoflavones can bind to these estrogen receptors.

The structure of isoflavones is not exactly the same as estrogen, so isoflavones are not estrogen. However, the isoflavone structure has important similarities to estrogen. These similarities allow isoflavones to bind to estrogen receptors in our estrogen-responsive cells. Don't take my word for it. Feast your eyes on the structure of these two molecules to see how they are similar (estrogen left, genisteiin right).


Because isoflavones come from plants, and because they are similar to estrogen, isoflavones are placed by scientists into a larger category known as phytoestrogens.

(Phyto = plant )

Q: What do soy isoflavones and other phytoestrogens have to do with puberty?

A: Puberty is the maturation of the reproductive system, and one important event in the final maturation of the reproductive system is the increase in synthesis and secretion of estrogens (a natural type of steroid hormone).

Puberty involves more estrogen binding to estrogen receptors, and isoflavones also bind to estrogen receptors.

Estrogens act on the brain areas that control maturation, menstrual cycles and fertility. They also act on the breasts, uterus, bones, fat cells, and parts of the brain involved in memory and other behaviors. Most of estrogen action is thought to happen when estrogen enters cells and binds to special estrogen receptors that lie inside the cells. The estrogen has a special binding site that allows it to recognize and bind to the estrogen receptor, like the way that a key (estrogen) fits its own special lock (estrogen receptor). The estrogen binds to estrogen receptors and form an estrogen-receptor complex (other molecules join in this complex). This estrogen receptor complex moves into the cell nucleus, starts a cascade of chemical reactions, which culminates in the estrogen-receptor (ER) complex sitting down on the DNA (yes, the genetic material). The effect of the ER complex sitting down on the DNA is to start turning genes on or off (this is called gene expression). Turning on a gene leads to the formation of a new protein (such proteins might be enzymes, hormones, or factors that turn on other genes). These changes in gene expression result in new proteins involved in puberty, fertility, bone growth, learning, etc. See my references at the end if you want to know more about estrogen action. (By the way, when the ER complex sits down on the DNA of some types of cancer cells, it promotes growth and cell division of those cancer cells.)

Q: If soy isoflavones bind to estrogen receptors, is this good or bad?

We don't have enough information to answer this. We do have enough information to say that the answer will not be a simple "yes" or "no."

In some cases, when isoflavones bind to the estrogen receptor, the effect is similar to the effect of estrogen. In other cases, isoflavones bind to the estrogen receptor and block the effects of estrogen.

Sometimes isoflavones mimic estrogen

Sometimes isoflavones block estrogen binding to its receptor

We know, for example, that treatment of female baby rats with estrogen will advance the onset of puberty, that is, puberty will occur earlier in the estrogen-treated rats. If soy isoflavones act like estrogen, we would expect rats fed isoflavones to reach puberty earlier than those that did not receive isoflavones. On the other hand, if soy isoflavones block the effects of estrogen when they bind to the estrogen receptor, we would expect puberty to be delayed in female rats given soy isoflavones.

Since estrogen rises at puberty, and puberty also involves changes in the body's ability to respond to estrogen, and many babies are raised on soy infant formula containing isoflavones, and the age of puberty has been decreasing over the past 30 years, it is reasonable to wonder whether the isoflavones in soy infant formula affect puberty. Do soy isoflavones advance or delay the onset of puberty? To perform this experiment on human babies is out of the question. This is why my student, Jamie Swanson and I fed baby hamsters the soy isoflavone genistein and monitored signs of pubertal development.

The results of our study on hamsters were very clear. Feeding the soy isoflavone, genistein advanced the onset of puberty. At the first ovulation we stopped the isoflavone treatment and two weeks later, we tested the females for sex behavior with a sexually-experienced adult male hamster. Those that had been fed the isoflavones were quicker to show sex behaviors characteristic of the adult female, suggesting that early isoflavone treatment has long lasting effects on the nervous system that affect behavioral motivation and performance.

Again, You can open a PDF of the whole study here.

Q: If you found that genistein advanced the onset of puberty in hamsters, does this mean that soy infant formula causes early onset of puberty in girls?

No. It simply suggests that more research should be done before giving soy infant formula to babies.

Please keep the following points in mind:

  1. This study was done in hamsters, and there is no guarantee that the effects of genistein in this study can be generalized to human beings.
  2. This study used only one isoflavone and cannot necessarily be used to generalize to other isoflavones (such as daidzein)
  3. This study gave a large dose of one isoflavone and cannot be used to generalize to soy infant formula or other soy products, which contains a variety of isoflavones at different doses. Some of those isoflavones mimic estrogen's effects, some of them block estrogen's effects, and the effects differ from tissue to tissue and species to species.
  4. The take home message from the hamster study is: Compounds in soy products have effects on the reproductive system in mammals, including long lasting effects on behavior, probably by binding to estrogen receptors.

You must draw your own conclusions from my study, but my conclusion is this:

More research should be done on soy isoflavones before feeding soy infant formulas to babies.

Q: Is there other research being done on soy infant formula?

Yes. Since my study was presented in 2001, many studies have been done on other rodents, nonhuman primates, and at least one small study was done on humans. The monkey and rodent studies have confirmed what our hamster study found, and the study on humans found no significant effect of soy infant formula on children's health including puberty. There are other studies in progress that will examine the long-term effects. Because the researchers want to know the long-term effects, the studies will take many years to complete. All of the references appear at the end of this FAQ sheet.

Q: Soy isoflavones come from natural organically grown nonmeat vegan-approved sources; how could they be harmful?

Lots of natural things are harmful (apple seeds, poison ivy, belladonna (deadly nightshade)). More important, soy milk and soy infant formula are about as natural as Coca Cola. The soy beans and the bean plants are "natural," but the products are unnatural. To make soy milk and formula, the beans are processed chemically to extract and concentrate the protein and fat components, which are then mixed with lots of sugar (quite often it's high fructose corn syrup, a whole other story). Soy milk and infant formula are more calorically dense than any "natural" food, including breast milk. When our pre-agricultural ancestors ate various beans and plants, they probably never experienced soy isoflavones at the high concentration of soy milk, nor did they consume liquid drinks with the high caloric value of soy milk. Soy milk, soy infant formula, tofu, tempeh, etc. are not natural, they are highly processed food products made from a natural bean.

Some people equate soy products with various "good" things such as fresh, unprocessed, organically grown vegetables, the healthy "Asian diet," and so forth. These people are under the erroneous impression that the makers and purveyors of soy products are in a different moral, ecological category than those in the meat and dairy industry. To the contrary, the soy industry is a huge agribusiness. Most soy is sold by Archer Daniels Midland, a Fortune 500 company quite well known for receiving enormous subsidies ("corporate welfare") and price fixing (see the Wikipedia entry for starters ). The soy lobby is one of the most powerful political lobbies, right on par with the meat and dairy lobbies.

The fact that soy beans are marketed by giant corporations doesn't make the beans good or bad, healthy or unhealthy. The point is, the vast majority of these soy products are not being sold and marketed by well-meaning, small, family farmers and gardeners with a commitment to your health. They are simply another kind of processed food with possible health benefits and possible side effects. Got soy?

Q: How can I make sense of all this?

You have to keep in mind the source of the information. All the information in the popular press is biased, both pro-soy and anti-soy. There are very dramatic anti-soy websites and publications, and these can be traced, usually, to meat and dairy industry/lobby types { here is one example of a rabid attack on soy }. The vast majority of what you see in the popular press is the positive spin on soy promoted by the soy lobby/industry and all the natural food industry people who benefit from selling soy products and selling you their own version of a "healthy" life stye. In addition, there is a pro-soy component of feminists who have fallen prey to the pro-soy lobby { here is an example of this uninformed point of view }


Here is what I think might be an objective website on soy (knock on wood).

For objective, primary scientific literature that is relatively free from the influence of corporations, you can search on your own for journal articles published by university scientists on PubMed or Google Scholar. These are not without bias, but at least the editors of these journals require all authors to make full disclosure of all financial interests. You can easily determine who sponsored the research (whether it was Archer Daniels Midland, the U.S. Food and Drug Administration or the National Institutes of Health) so you can see through to the motivations that underlie the research.

On a related topic, it is important to know that one reason our government gives research grants to university scientists is so that we can do controlled experiments to try and answer these questions without having industry influence the outcome of the experiments and without having industry influence our ability to disseminate the results. As corporations become more and more involved in government-funded research projects, this essential objectivity will diminish rapidly.

Q: My daughter reached puberty very early and I raised her on soy infant formula; should I feel guilty?

No. But, I'm a mom too, and one of my children has had a multitude of medical issues, so I certainly empathize with your feelings.

A few more useful points: The one small study that has been done on human infants found no significant effect of soy infant formula on children's health including puberty. In addition, there are many, many environmental factors that might cause precocious puberty in any particular child. It is impossible for any one individual to know which one was the culprit. There are many different molecules that bind to estrogen receptors or turn into molecules that bind to estrogen receptors, and any one of these might influence the developing reproductive system (see this link):

  • Pesticides (chlordane, toxaphene, etc.)
  • Plastics (such as bisphenol and pthalates which leach out of plastic into food)
  • Effluent from industrial waste (nonyl phenol, dioxin, PCBs)
  • Hormones given to farm animals that we eat (dexamethasone)
  • Real estrogen and progesterone that are ingested as birth control pills and then excreted into the toilet, which then end up in our drinking water (water treatment systems clean up bacteria and other contaminants, but not steroids such as estrogen)

Feeling better? I know, it's depressing. We live in a " sea of estrogens " that are contributing to the increase in precocious puberty, hypospadia, ambiguous sexuality, infertility, cancer and who knows what else. At the same time, soy isoflavones are being sold to us as though they will protect against symptoms of menopause, osteoporosis, heart disease breast cancer, etc. The best you can do is keep learning. I will try to keep this site updated for you.

Thanks for your emails, and I'm sorry I cannot answer each one individually.


Casanova, M., You, L., Gaido, K. W., Archibeque-Engle, S., Janszen, D. B., and Heck, H. A. (1999). 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 51(2), 236-44.

Giampietro, P. G., Bruno, G., Furcolo, G., Casati, A., Brunetti, E., Spadoni, G. L., and Galli, E. (2004). Soy protein formulas in children: no hormonal effects in long-term feeding. J Pediatr Endocrinol Metab 17(2), 191-6.

Levy, J. R., Faber, K. A., Ayyash, L., and Hughes, C. L., Jr. (1995). The effect of prenatal exposure to the phytoestrogen genistein on sexual differentiation in rats. Proc Soc Exp Biol Med 208(1), 60-6.

Piacsek, B. E., and Streur, W. J. (1975). Effect of exposure to continuous light on estrogen-induced precocious sexual maturation in female rats. Neuroendocrinology 18(1), 86-91.

Tan, K. A., Walker , M., Morris, K., Greig, I. , Mason, J. I., and Sharpe, R. M. (2006). Infant feeding with soy formula milk: effects on puberty progression, reproductive function and testicular cell numbers in marmoset monkeys in adulthood. Hum Reprod 21(4), 896-904.