Conscious Choice: It's Soy Confusing

May 2000 | Health Conscious

It's Soy Confusing

by Rebecca Ephraim, RD, CCN

As a nutritionist, I’ve been extolling the virtues of soy for a number of years. Eat it! Always eat it! Soymilk on your cereal, soymilk in puddings, tofu scramble, tofu salad, veggie burgers, edamame (boiled soybeans), soy nuts, soy butter. Mercy! Could there be a food that is more promoted for its healthful qualities?

Well, now comes news that soy consumption should be approached with caution. But how much caution is the question. Regardless of what you’ve read or heard in the last month, I, personally, am not issuing a shrill alarm or hitting you with a two-by-four between the eyes. Consider this a whisper or a gentle tug on the sleeve. In the scientific community, there have been hints of concern about soy foods. Regardless, I must emphasize that, all in all, if you add up the informed opinions of the numerous researchers and scores of studies that have been done there is no question that they still slant sharply toward the idea that soy is good for you. What I’m about to discuss are the studies that suggest we should not consider soy the invincible guardian of our good health.

The hype over soy leaped into overdrive last October when the U.S. Food and Drug Administration (FDA) allowed food companies to claim that soy protein helps reduce cholesterol and the risk of heart disease. But keep in mind that, generally, in the world of science and research, selective studies can be chosen to make a case. For instance, visit the United Soybean Board’s web site (www.talksoy.com), and you’ll see well-documented articles written by thoughtful scientists touting the health benefits of soy products from "lowering risk of cancer, osteoporosis, and other chronic diseases to easing the symptoms of menopause."

But outside the spotlight of all this hoopla are other scientists checking in with significantly different research results. These are unsettling studies that have been quietly pushed off the stage so that all eyes can be directed toward the amazing soybean and its magical powers. In fact, depending on what research you read and which scientists you talk to, it’s as if the remarkable soybean has an evil twin.

Probably the most prominent research that’s evoking these suspicions is the newly published work of Lon White, M.D., at the Pacific Health Research Institute in Honolulu. Dr. White’s ongoing study of 3,734 Hawaiian men over more than thirty years suggests that regular consumption of tofu over many years during their middle age was associated with early dementia or what Dr. White terms "accelerated brain aging."

White’s study, entitled "Brain Aging and Midlife Tofu Consumption," hit the media last month as it was released in the April 2000 issue of the Journal of the American College of Nutrition. It is a long-range study charting the eating habits of the men since 1965. Final assessments were made of their cognitive functioning (e.g. thinking, learning, memory) along with tests for measuring brain atrophy or shrinkage. The stunning conclusion was that the men who ate two or more servings per week of tofu had steeper declines in brain functioning resulting in dementia.

Despite the dramatic results of his work, Dr. White told me in an interview, "I would be violating a cardinal rule if I said my data says you shouldn’t eat tofu [or other soy foods]." Of course any reasonable human being unfamiliar with the dictums of science would find this totally perplexing. Yet it needs to be understood that even though Dr. White believes his research is solid, the results, he says, "can’t be turned into sweeping conclusions and the findings must be considered only preliminary."

Dr. White’s study was of an observational nature in which the participants chose their lifestyles. He says his findings demand further investigation through more randomized trials. For example, study subjects (humans or animals) would be randomly divided and one group would be fed tofu and the other would not. The incidence of dementia in the two groups would then be measured and compared. A progression of such studies would either confirm or refute Dr. White’s findings. He believes it will take at least ten years for a conclusion.

On another front, two FDA-affiliated scientists wanted the agency to put the brakes on the proposed health claim label for soy protein. They cited numerous studies that demonstrated toxicity and other ill effects from the use of soy. Before the labeling decision was made, Daniel Sheehan, Ph.D., and Daniel Doerge, Ph.D., both from the FDA’s toxicology research center, wrote, "We oppose this health claim because there is abundant evidence that some of the isoflavones found in soy...demonstrate toxicity in estrogen-sensitive tissues and in the thyroid." (Isoflavones are plant chemicals that have estrogen-like hormonal effects on the body.) In their letter, the researchers cited twenty-eight studies, including Dr. White’s, that point to possible risk factors. There was various research suggesting that consuming soy isoflavones could be a risk factor during pregnancy for abnormal brain and reproductive tract development in the fetus, thyroid abnormalities in infants and adults, and the possibility of increased risk of breast cancer.

In its considerations for approving the health claim, the FDA dismissed nearly all the negative studies, saying either the evidence to make these claims was very limited or that there was a need for additional research. In fact, much of the concern was based on animal studies and, in the instances of breast cancer there’s no clear association. University of Minnesota scientist Mindy Kurzer, Ph.D., who does extensive research in the area, says there are no data connecting soy and cancer, "There’s a theoretical risk that soy might promote breast cancer in some way but it’s purely theoretical at this point." To date, one of the more definitive studies, in the American Journal of Clinical Nutrition (December 1998), concluded that soy increases cell production in human breast tissue. An increase in cells has been associated with an increased chance for developing cancer cells. But Kurzer is right, that does not mean soy causes cancer.

Obviously then, the blaring question is "How much soy should or can I eat?" I am aware of nutritionists who, based on the accumulated research, are taking no chances with their clients who either have had breast cancer or who are predisposed toward it. They simply tell these clients to avoid soy. Other professionals and researchers are concerned with concentrated amounts of isoflavones, the components of soy that have been singled out as the potential culprits for health risks. Soy concentrates in the form of dietary supplements such as pills, powders, and sports bars have higher levels of isoflavones.

Given the conflicting data, Dr. Kurzer recommends that we "not go overboard." She says, "Consume soy foods in an amount on the order of what people in Asia consume, about one or two half-cup servings a day. There’s no reason why anyone should eliminate soy from their diet." FDA toxicologist Barry Delclos, who’s been testing soy compounds, says, "There is no clinical evidence for adverse effects from consuming soy." Even Daniel Doerge, one of the researchers who wrote the letter to the FDA, suggests eating soy as part of a "balanced diet."

Soy products have always been a valuable substitute for meat because they are so versatile and easy. As a modified vegetarian (I do include some free-range animal protein in my diet), I know the importance of soy, as it is the only vegetable that has the same protein quality as milk and meat. But given the fuzzy emerging information, each of us has to weigh our own health circumstances and make an informed decision with regard to how much soy we eat.

Given the uneven media hype over soy you may want to visit www.soyonline service.co.nz, a web site dedicated to sharing information about the negative impacts of the consumption of soybeans. This web site is a little too aggressive for my tastes but has a responsible compilation of research that gives both sides of the story.

Disclaimer: This column is for information only and no part of its contents should be construed as medical advice, diagnosis, recommendation or endorsement by Ms. Ephraim.

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