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By SYD BAUMEL

The Smoking Biochemical Gun

But what if this is all much ado about nothing, and White's study is an anomaly that will go away when others take a closer look? Unfortunately, there is a smoking biochemical gun that suggests it ain't no fluke.

Soy is prized as a health food mostly because of its exceptionally high content of isoflavones, of which genistein is the major one. Like other isoflavones, genistein is a very weakly estrogenic chemical—a "phytoestrogen" (plant estrogen) capable of acting like the hormone estrogen in the human body under some conditions but of acting like an estrogen decoy—with anti-estrogenic effects—under others. Isoflavones, White explains, "are molecules that the soy plant makes while it's germinating to help it fend off mold and other things." But in the human body these same chemicals "inhibit certain kinds of enzymes and alter . . . metabolism."

"The bottom line," White bluntly concludes, "is these are not nutrients. They are drugs. They will have some benefits and some negative things."

When it comes to men's brains, our neurons have receptors both for male hormones (androgens), like testosterone, and for estrogen, White points out. Indeed, not only do men manufacture a touch of estrogen, in the brain we even have an enzyme that goes out of its way to convert androgens into this "female" hormone. As research suggests it is for women, estrogen may be a kind of smart hormone for men too. But phytoestrogens—White's study suggests—may act more like fake estrogens than real ones in the brain, like dumb hormones.

Estrogen itself is known to be a two-edged sword, warding off osteoporosis, heart disease, and perhaps dementia, among other conditions, on the one hand, but fuelling certain cancers on the other. So far, phytoestrogens (PEs) have enjoyed a popular reputation as a "one-edged sword," as if they knew just when to speak up (duplicating estrogen's benign effects) and when to shut up. And indeed, they are moderators of estrogenic activity. In the body, their extremely weak estrogenicity inclines them to dilute high estrogen activity and augment very low. Thus, there is evidence that PEs can—anti-estrogenically—prevent estrogen-related cancers like breast cancer and—estrogenically—prevent or allay prostate cancer, osteoporosis, atherosclerosis, and the estrogen-withdrawal symptoms of menopause.

But some research (not just White's) suggests that genistein and perhaps other PEs have a dark side, that there's no free lunch, even if it's 100% organic, non-genetically modified soy. That soy can kill cancer cells hints at the source of the problem. Genistein does so by interfering with DNA synthesis in these renegade cells. But what if healthy cells are affected too?

Such was the case in a recent test tube study from Sweden. Genistein inhibited the growth of young rats' grey matter (the "smartest" part of the brain: the cerebral cortex) by inhibiting DNA synthesis. Until very recently, this would not have raised any concerns for adult humans. After all, we stop sprouting new brain cells (neurons, to be exact) in childhood, anyway. Right?

Wrong. Last year, E. Gould and associates at Princeton University discovered that our fellow primates, the macaques, continue to produce new neurons right into adulthood—neurons that migrate to higher centres in the cerebral cortex (also reported in The New York TImes). And in humans, researchers at the Salk Institute have "found evidence of recent cell division in a part of the brain called the hippocampus in every person studied," according to an article last year in Parade Magazine (November 21, 1999, pp. 10-13). The hippocampus is not just any brain centre. It's memory central—the front lines of dementia.

So a surfeit of soy could be stifling the brain's renewal of its memory-making neurons. Moreover, as Goddard points out, "reduced DNA synthesis promotes apoptosis, which is also known as 'programmed cell death.'" So a surfeit of soy could be killing off old neurons too. It's enough to make vegetarians like Goddard and myself just say no to "the more soy, the better" credo.

But that's not all.

The Hypothyroid Problem

Ironically, women who take soy to salve the symptoms of menopause may be opening the door to another common midlife health woe: hypothyroidism.

"Taking 40 mg of isoflavones causes hypothyroidism in susceptible women . . . and I mean those in transitional menopause, the new word for perimenopause," says Larrian Gillespie. "I tried the experiment on myself and developed full blown hypothyroidism in 10 days."

Gillespie's words could hardly be more counterrevolutionary. But they carry weight, for Gillespie is a medical doctor, the author of several books on women's health, including The Menopause Diet. Her observations are echoed by testimonials from other women who developed "goitres" (swollen thyroid glands due to hypothyroidism) soon after beginning an aggressive dietary and/or supplemental soy regime at the very time of life when women are most vulnerable to the debilitating, depressing disease. Soy's ability to cause hypothyroidism has, in fact, been documented for generations. The bean is a well-known "goitrogen"; its isoflavones compete with the enzyme that synthesizes thyroid hormone from tyrosine and iodine.

In a 1991 study from Japan by Ishizuki et al., just 30 grams of soybeans were added to the daily diet of 37 healthy subjects. The 17 who followed this regime for three months developed (as a group) laboratory signs of mild or subclinical hypothyroidism. Half even had clinical symptoms—including goitres—all of which disappeared a month after the soybeans were discontinued. The ten older subjects were most vulnerable to the goitrogenic effect.

No, No, Not the Nursery Too!

It's one thing to enfeeble the minds of old men or sap the vitality of middle-aged women, but babies?
According to Dr. Patrick G. Tuohy of the New Zealand Ministry of Health, there have been a dozen case reports of childhood hypothyroid abnormalities associated with soy formulas since the 1950s. A 1990 study from Cornell University Medical College found that 59 children with autoimmune thyroid disease had had nearly three times as much exposure to soy-based milk formula as a healthy control group. However, Tuohy asks, were the children fed more soy because they were immunologically more reactive (e.g., allergic to milk or beef) to begin with? Tuohy also wonders why there are so few case reports of childhood hypothyroidism, despite the popularity of soy formula. Yet it's possible that very mild, subclinical thyroid impairments could be dulling children on soy-rich diets without anyone even noticing.

And there could be other untoward hormonal effects. A 1997 U.S. study by Setchell et al. found that infants on soy infant formulas were sucking down six- to eleven times as many phytoestrogens as the amount known to have hormonal effects in adult soy eaters (based on equal bodyweight). Could there be adverse effects? Soy critics like Soy Online Service and the Weston A. Price Foundation cite a Puerto Rican study in which soy infant formulas were among several factors implicated in a mysterious epidemic of premature thelarche (breast development). Premature thelarche is associated with early menarche, which in turn is associated with a greater risk for breast cancer and ovarian cysts, the latter being a risk factor for ovarian cancer.

As if phytoestrogens weren't enough to worry about, it turns out that manufacturing soy-based infant formulas "enriches" them with a toxic heavy metal. INFACT (Infant Feeding Action Coalition) Canada is dedicated to replacing all infant formulas with breastfeeding. They report that in 1990, "Health Canada, after testing the levels of aluminum in soy-based formulas, reported that infants fed these products ingested on average 1260 [micrograms]/day compared to 2-3 [micrograms]/day for infants fed human milk." A 1995 study from the Institute of Child Health in London found a smaller 50-fold difference (other baby formulas, it should be noted, were not much better—and one was worse). Though this is not a high intake compared to other sources, like aluminum-containing drugs, researchers are worried it could be the last straw for babies with poor kidney function. Aluminum is especially toxic to brain and bones.

In a 1998 position statement, The Australian College of Pediatrics wrote: "There is some evidence that soy formula may impair immunity, and the long-term effects of contaminants of soy (e.g. aluminum and phytoestrogens) are unknown." The College recommended that soy formula only be used in infants with medically confirmed galactosemia or lactose intolerance. That same year, the New Zealand Ministry of Health also recommended a use-only-if-medically-necessary approach—and check the child's thyroid if there are any signs of retarded development. Also that year, Daniel Sheehan of the FDA's National Center for Toxicological Research cautioned that "among human exposures, infant soy formula exposure appears to provide the highest of all phytoestrogen doses, and this occurs during development, often the most sensitive life-stage for induction of toxicity. Large, carefully controlled studies in this exposed infant population are a high priority."

Alas, soy's threat to children likely begins even before they're born. In a recent study from Cedars-Sinai Medical Center, genistein was fed to pregnant rats. Their offspring—both male and female—were masculinized, the male pups entering puberty early. The study's lead researcher, Claude Hughes, speculated that in people whose pregnant or nursing mothers eat too much soy "there may be subtle changes, such as [in] neurobehavioral attitudes, immune function and sex hormone levels."

What to Make of it

"With  my refrigerator full of soy stuff," writes ethical vegetarian Ian Goddard, "I wish I could be sure now, but until the soy picture gets clearer, the evidence is enough for me to be inclined to err on the side of caution. However, it should be noted that the research indicating an anticancer potential for soy is consistent, and research shows that the cytotoxic [cell killing] properties of soy products are strongly specific, but apparently not entirely exclusive, to cancer cells. If I had terminal cancer, I would consider using soy products!"

Goddard seems to have a well-tempered attitude to the "what now?" implications of this soy confusion. If soy is medicinal, why should we assume it can't cause adverse effects? At levels beyond a very moderate intake, soy may—like drugs or medicinal herbs—need to be "used only as directed." (Speaking of which, soy's antithyroid effect can likely be prevented by a diet rich in iodine from sea vegetables, like kelp, or supplements.)

"Individuals will have to weigh the evidence and make their own decisions concerning their consumption of soy foods and their isoflavone derivatives," concludes White.

That said, soy foods that are low in isoflavones/phytoestrogens may be used less "cautiously": soy sauce, soybean oil, some soy protein concentrates, and foods only partially made of soy, like those veggie burgers you . . . love so much. Some would-be experts, like Soy Online Service and the equally anti-soy Weston A. Price Foundation ("there is no joy in soy—it’s a ploy" is their motto), believe that soy, as traditionally prepared, fermented, and moderately consumed as a condiment in the Orient in the form of miso, tempeh, and soy sauce, is less threatening than mass quantities of soy, straight up. Indeed, a touch of soy, they admit, may even be good for you.

Soy-bashing reaches a new low in this deceptive diatribe. Reviewed by Syd Baumel.

Here are a few articles that take a more positive view of the embattled health food: 

Response To Misleading Article About Soy In Mothering Magazine - by John Robbins (2004)

Is Soy Safe? - Brenda Davis, R.D. (2003)

Is It Safe to Eat Soy? - by Virginia Messina, MPH, R.D. and Mark Messina, Ph.D (circa 2003)

Is It True What They Say About Soy? - UC Berkeley Wellness Letter, 2002

What about Soy? - by John Robbins, circa 2000