Built Ford tough
At the 1934 World’s Fair in Chicago, automobile magnate Henry Ford hosted a special dinner featuring 16 dishes, all made from soy. Guests at that dinner generally agreed that soy didn’t have much of a future as a food source. But Ford went on to devote millions of dollars to the development of many different kinds of soy products. He even made car parts out of soy. And in spite of the poor reception at the World’s Fair, as we now know, his efforts to promote soy as a food eventually paid off.
Just check a few “Nutrition Facts” panels in your pantry. You’ll see that the average American diet contains traces of soy from a wide variety of sources – literally: from soup to nuts. But is it the miracle food that Ford promised it would be? The answer to that depends on who you talk to.
In two e-Alerts I sent you a little more than a year ago, I told you about some of the controversies along with the pros and cons surrounding soy and soy products. Recently, I came across a nutrition study that draws an impressive conclusion about one of the benefits of soy. But does the conclusion hold up under scrutiny?
Slinging soy in Singapore
Soy has been a staple in the Asian diet for thousands of years. Because some soy products have been shown to lower estrogen production, and because lower estrogen levels are associated with a lower risk of breast cancer, it’s generally believed that the far lower incidence of breast cancer in Asia, compared to the West, could be due to the far higher soy intake among Asian women.
This was the basis of a recent study conducted by a research group from the University of Southern California. WebMD Medical News reported the study with this headline, sure to appeal to all women: “Eating Lots of Tofu may Prevent Breast Cancer.” But a closer look reveals that this headline is more optimistic than it deserves to be.
The USC team used questionnaires to analyze the diets of 144 Singapore women who were all postmenopausal. Their findings show that the women who had the highest consumption of soy had 15% lower levels of estrone – one of the three forms of estrogens present in the female body. According to the researchers, their analysis suggests that soy intake is associated with a reduced risk of breast cancer in postmenopausal women.
So should postmenopausal women start loading their refrigerators with soy milk and bricks of tofu? The researchers make no such recommendation. But the lead author of the study, Anna H. Wu, Ph.D., told WebMD Medical News that she was “not aware of any studies showing harmful effects from eating soy foods.”
Frankly, it’s hard to believe that a soy researcher would not be aware of the potentially harmful side effects of soy, as demonstrated in a number of well known studies.
The whole soy story
The USC study noted that there was apparently no drop in the estrogen levels of women who ate “average” amounts of soy foods. Keep in mind that an average intake of soy in Singapore is much higher than the average in the U.S. So in order to reap any breast cancer preventing benefits from soy, a woman would have to increase her soy intake enormously to reach that upper percentile of the USC study group. And that increase of soy could have a number of unwelcome side effects.
For instance: in an e-Alert I sent you in September last year (“Research Shows Health Risks of Soy Likely Outweigh Benefits”) I told you about a study that identified a possible link between soy consumption and kidney stones. That study, from the Journal of Agricultural and Food Chemistry, showed how soybeans, tofu, and commercially processed soy products contain an extremely high amount of oxalate, a compound that binds with calcium in the kidneys, increasing the risk of kidney stone development.
If only that was the worst of it.
Contradictions & complications
In that September, 2001, e-Alert I also quoted two researchers with the National Center for Toxicological Research, Daniel Sheehan, Ph.D., and Daniel Doerge, Ph.D., who said, “There is abundant evidence that some of the isoflavones found in soydemonstrate toxicity in estrogen-sensitive tissues and the thyroid.”
Sheehan and Doerge cited a study of pregnant Rhesus monkeys. The study group, which was fed genistein (a chemical compound found only in soy products), had levels of estradiol (another of the three forms of estrogen) 50 to 100 percent higher than the control group. Because estrogens create a significant risk factor for breast cancer, the increased amount of estradiol suggests that soy intake may actually CONTRIBUTE to the risk of breast cancer.
But the possible risks go even further. In one of the largest and better known soy studies (reported in the Journal of the American Medical Association), 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 almost two and a half times more likely to develop vascular dementia and brain atrophy.
The middle way, for now
So where are we? Is soy good, or bad? Does soy intake prevent breast cancer, or does it bring a high risk of breast cancer and other health problems? It’s no wonder that Dr. Jonathan Wright (editor of the Agora published newsletter “Nutrition & Healing”) poses the question, “Is soy protein a kind of Dr. Jekyll and Mr. Hyde?” Dr. Wright notes that there are undeniable benefits to eating soy (high protein, low saturated fat, easy on the stomach), as well as some potentially dangerous side effects.
Because the dangers of soy seem to depend on the amount consumed, more studies are needed to determine safe levels of intake. And without question, many more studies are underway. I’ll be on the lookout for those reports, as well as any other new soy information that comes along, because, like it or not, soy is a part of the diet of anyone who eats processed food – which is to say: almost all of us.
In the meantime, if you enjoy adding tofu to your stir fry, or if you can’t resist that bowl of miso soup at your favorite sushi restaurant, don’t feel you’re in grave danger if you indulge. But until we have conclusive evidence one way or another, it would probably be a good idea to keep your soy intake at a moderate level.
To Your Good Health,
Jenny Thompson
Health Sciences Institute
