Research shows health risks of soy likely outweight benefits

“Why do you still eat soy?”

That was the question someone asked me after she read the original draft of this e-Alert. And I didn’t know what to say to her.

The simple answer is that I don’t eat meat, and eating soy makes that a lot easier. I can adapt a lot of my favorite recipes using soy, and it’s becoming commonplace to find meat substitutes in restaurants and grocery stores. (My sister and I joke that you have to love a food that can be ice cream or tuna fish.) So for a vegetarian, soy is convenient. And when you eat it long enough, it even seems tasty.

But the answer isn’t simple when you consider the mounting indicators that soy is anything but health food.

When I first sat down to write to you today, I was focusing on a new study being published in the September issue of the Journal of Agricultural and Food Chemistry. It identifies a possible link between soy consumption and kidney stones. According to the study, researchers have found extremely high oxalate contents in soybeans, tofu, and commercially processed soy products.

Oxalate is a compound that binds with calcium in the kidneys and can lead to the development of kidney stones. The American Dietetic Association recommends no more than 10 mg. of oxalate per serving. Soy cheese had the lowest amount at 16 mg. per serving, while textured soy protein had an astounding 638 mg. per serving – nearly 64 times the maximum amount recommended. Based on these figures, researchers concluded that soy products are simply unsafe for anyone at risk for kidney stones.

Because I eat a lot of soy, I’ve been following the growing controversy about its safety. A majority of us, after all, are not at risk for kidney stones. But there is evidence that soy may contribute to vascular dementia, breast cancer, interference in thyroid function, osteoporosis, and other serious and potentially deadly diseases.

The FDA has approved soy’s health claim for managing coronary heart disease. However, many people are not satisfied that the benefits are enough to offset the growing list of risks.

In a letter protesting the FDA’s decision to grant the health claim, Daniel Sheehan, Ph.D., and Daniel Doerge, Ph.D., both of the National Center for Toxicological Research, wrote, “We oppose this health claim because there is abundant evidence that some of the isoflavones found in soy, including genistein and equol,demonstrate toxicity in estrogen-sensitive tissues and the thyroid.” (Isoflavones are a type of phytoestrogen present in chick peas and legumes.)

Sheehan and Doerge cited one study of pregnant Rhesus monkeys. The study group, which was fed genistein, had serum estradiol levels 50 to 100 percent higher than the control group. Since a woman’s own estrogens are a significant risk factor in breast cancer, the increased amount of estradiol (one of the three estrogens present in the female body) strongly indicates how soy may contribute further to this epidemic.

In one of the largest and better known soy studies, researchers monitored 7,000 Japanese-American men in Hawaii over a 30-year period, measuring their level of soy consumption throughout. Those who ate two or more servings of soy a week were up to 2.4 times more likely to develop vascular dementia and brain atrophy. (Details of the study can be found in the Journal of the American Medical Association, vol. 276.)

Since the dangers of soy seem to be dose-dependent, more studies need to be done to determine if soy consumption is safe at any level, but consider the following:

HSI Panelist Allan Spreen, M.D., sent us to the website for the Weston A. Price Foundation, according to which:

  • Soy phytoestrogens interfere with endocrine production and have the potential to cause infertility and breast cancer in women.
  • Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and can lead to thyroid cancer.
  • Soy foods contain high levels of aluminum, which has been linked to dementia and Alzheimer’s disease.
  • Soy beans, as grown, are toxic to humans and not safe for consumption.

Well-known alternative medicine pioneer, Jonathan V. Wright, M.D., is also among those to question the safety of soy. According to him, processed soy powder contains residual phytic acid, a substance experts know blocks the absorption of calcium, magnesium, zinc, and other essential minerals in the intestinal tract.

Further, feeding experiments have shown that a soy-based diet requires supplementation with vitamins E, K, D, and B12, and creates significant deficiencies in copper, iron, zinc, magnesium, and calcium. This is especially important for post-menopausal women, who by eating soy or taking soy supplements as a form of natural HRT, could be putting themselves at risk for nutritional deficiencies and osteoporosis. It is also important to those of us who don’t eat meat, as we tend to be B12 deficient.

As someone whose diet is largely soy dependent, often eating two servings per day, let alone per week, I am going to continue to research this aggressively. And as I know many of you are incorporating soy either into your diet or your supplementation program, I will share everything I uncover. I would invite you to write in with any information you may have on the dangers or safety of soy so I can share it with the rest of our network.

As for me, I plan to immediately curb my consumption (if not eliminate soy protein altogether). Lately I have been considering re-introducing meat into my diet and this may end up being the catalyst for it. If you have any advice about a healthy way to do that or any personal experience to share, I would love to hear back from you.