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 *** 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' *** 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