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The Story on Soy
Q: I’ve heard a number of views on soy. Some seem to think it’s the best thing since sliced bread, that it cures just about everything, and others say it’s bad, that it inhibits muscle growth and may even promote cancer. What’s your take?
A: Newsweek magazine said not long ago that soy is "great food but only modest medicine." That about sums it up. Soy is an excellent source of protein and other nutrients, but the jury is still out on its health benefits.
Nikkei and David Goldbeck, co-authors of The Healthiest Diet in the World (Plume, 2001), are big boosters of soy foods. "Soy’s exemplary nutritional profile mandates its inclusion as a prominent part of everyone’s diet," the Goldbecks’ write. They’re also very impressed with the health potential of soy foods, but caution "that current enthusiasm in the media sometimes surpasses the data."
Walter C. Willett, M.D., chairman of the Department of Nutrition at the Harvard School of Public Health and author of Eat, Drink, and Be Healthy (Simon & Schuster, 2001), is less enthusiastic. "I’m still a bit cautious about soy, especially about eating a lot of it," writes Dr. Willett. "Soy may have a dark side," he warns.
Unique Nutritional Profile
I first learned that soybeans are special in the ‘50s as a budding young lifter reading Bob Hoffman’s articles on nutrition in Strength & Health magazine. Hoffman promoted his Hi-Proteen (that’s the correct spelling) as a wonder food capable of building muscles at a pace never before attained. The primary ingredient in Hoffman’s Hi-Proteen was soybean flour.
According to Muscletown USA, the history of Bob Hoffman and the York Barbell Company by Professor John D. Fair (see article # 32), Hoffman traced his fascination with soybeans back to 1914, when he started patronizing Chinese restaurants. Hoffman said he began growing soybeans on his Pennsylvania farm in the 1930s. I don’t recall the background spin. All I remember is that soy protein was supposed to help me get bigger and stronger. Bob Hoffman obviously made a believer of me, because I bought so much Hi-Proteen that the health food store gave me a discount.
Hoffman said he spent years trying to find the right formula. The main problem seemed to be that a soy-based product didn’t taste very good. Hoffman wrote in Strength and Health: "We took our problem to chemists, laboratories and food processors and finally developed the product which is now known as Hoffman’s Hi-Proteen."
That was probably a bit of a stretch, according to Fair. He quotes Jim Murray, editor of Strength and Health, as painting quite a different picture. Murray says Hoffman got the idea for Hi-Proteen from a Chicago gym owner named Erwin Johnson. Hoffman sold Johnson’s product just long enough to assess the demand and then replaced it with his own. According to Murray, Hoffman ordered sweet chocolate from Hershey and mixed up the first batch "with a canoe paddle in a soy bean flour container." Shocked by the lack of scientific process, Murray says Hoffman was "sweating away while stirring and tasting, saying ‘yuk, no one will buy that,’ and so mixed more." Whatever the truth, soy-based protein supplements have been selling well ever since. And not without substantial scientific justification.
As I recall, Hoffman -- correctly -- emphasized the high-quality of the protein in soybeans. Unique among plant foods, soybeans supply all the amino acids needed by the human body for growth and repair. Soybeans would apparently suffice even if they were the only dietary source of protein. According to the Goldbecks, their biological value is comparable to that of beef or milk.
Soy protein is better than that found in other beans, according to the Goldbecks, because it contains an abundance of the essential amino acid tryptophan. The protein is also more concentrated. "Soybeans have about twice the protein content of other beans, such as chickpeas, kidney beans, or lentils," the Goldbecks write. Nevertheless, they add: "In our opinion, as with any food, soy is meant to be a part of a varied diet, and not the sole or necessarily even the principal protein." (More on that later.)
Andrew Weil, M.D., is also favorably disposed toward soybeans. "Of all the legumes, soybeans deserve the most attention," Weil writes in Eating Well for Optimum Health (Knopf, 2000). "Not only are they high in protein, they have a heart-healthy oil that includes omega-3 fatty acids." One of the pluses of soy protein is that it comes without the high level of saturated fat found in red meat and many other animal sources. "Substituting [soybeans] for some of the animal foods in the standard Western diet would be a healthy change," says Dr. Weil, "perhaps one of the most healthful changes you could make."
Soybeans are one of the few plant foods containing significant amounts of fat. The Goldbecks and Dr. Weil believe that’s a good thing. Jeff Novick (Chef Jeff), Director of Nutrition at the Pritkin Longevity Center and a strong proponent of very low-fat diets, disagrees. In his online Weekly Health Update, Novick wrote: "Most beans are about 1 % fat, while the soybean is about 18-20 % fat, of which 15 % is saturated."
Novick insists that other beans are as good or better than soybeans. He says: "Soy is neither unique in protein nor isoflavone content." According to Jeff, soybeans contain twice as much omega-6 fat as omega 3. "Omega-6 fats have effects on lipid oxidation and blood clotting," says Jeff, "but it is still not clear whether this is beneficial or not."
There must be others, but Novick is the only nutrition expert I know to worry about the fat content of soybeans. As noted above, Dr. Weil praises the "heart-healthy" fats found in soybeans. Referring to the desirability of substituting soy foods for animal foods, Weil writes: "At one stroke, you would decrease intake of saturated fat and increase omega-3s, fiber, and protective phytochemicals." Weil warns against highly processed soy foods, such as "isolated soy protein," which he says "may not contain the isoflavones, fiber, and healthful oil of the whole bean."
Health Benefits Puzzle
"For a while it looked like, ‘oh my gosh,’ soy is the answer to everything," researcher Margo Woods of Tufts University School of Medicine told Nutrition Action Health Letter. "But the more research that’s been done, the more things got complicated."
The one area of general agreement is that soy can help control blood cholesterol. A review of 38 studies reported in the New England Journal of Medicine showed that eating a lot of soy protein in place of animal foods such as beef and poultry lowered triglycerides and LDL-cholesterol, while keeping "good" HDL-cholesterol the same.
In a later study of 156 people, Professor John Crouse III of the Bowman Gray School of Medicine found that this works best for people with very high cholesterol who eat foods made from whole soybeans. "You need isoflavones together with the protein," Crouse told Nutrition Action Health Letter.
Crouse found that people with "bad" LDL-cholesterol over 160 and those given soy protein with 62 mg of isoflavones responded best. Those with LDL-cholesterol between 140 and 160 and those given soy protein with less than 37 mg of isoflavones did not show a significant drop in cholesterol. This, of course, reinforces Dr. Weil’s warning against highly processed soy foods.
(Professor Crouse says soy works best when used in conjunction with an otherwise healthy diet and exercise.)
The heart-health benefits of soy may not stop there. The isoflavones in soy are phytoestrogens: weak estrogen-like substances made by plants. It’s well known that estrogen protects premenopausal women against heart disease. It seems to improve the elasticity of arteries and slows atherosclerosis, or clogging of the arteries. Many researchers believe that soy phytoestrogens may have the same heart benefits.
The evidence is far from clear, but soy may also lower the risk of breast cancer. According to Tufts University Health & Nutrition Letter, the prevailing theory is that soy phytoestrogens may mimic some of the action of human estrogen -- which can stimulate the growth of cancer cells – but are much weaker, enabling them to provide some of the normalizing benefits of the hormone without the harmful side effects.
The Goldbecks explain how most researchers believe this works: "The potency of phytoestrogens is just a fraction of that of human estrogen. While they’re close enough in structure to fit into the estrogen receptors, they’re too weak to stimulate them. By acting in a competitive manner, they block the entry of the more potent cancer promoting hormone."
Likewise, in men, soy estrogens may block the growth effect of testosterone on prostate tumors.
Testosterone is responsible for the development of numerous male characteristics, but once a man develops prostate cancer, testosterone can hasten its progression. Phytoestrogens may slow or prevent the cancerous growth by harnessing testosterone.
Again, the Goldbecks explain how this could work: "One theory is that estrogen slows down production of the male hormone testosterone, [and has been used successfully] to treat prostate cancer. If phytoestrogens act like estrogen, they can perhaps have the same effect.... In addition, there is good experimental evidence that isoflavones inhibit an enzyme that converts testosterone to a more proliferate form within the prostate itself."
These theories find support in the history of Asian men, who eat far more soy then we do in the West and have dramatically fewer deaths from prostate cancer. "It isn’t that Asian men aren’t afflicted with this cancer," the Goldbecks explain. "In fact, autopsies indicates similar incidence in both populations. But their tumors grow so slowly that the Asian men tend to die from other causes long before the tumors become lethal."
Happily for male bodybuilders, the Goldbecks add this important bit of information: "Men might be comforted to know that although phytoestrogens may altered testosterone’s activity, unlike hormone therapy, they do so without compromising masculinity."
For what it’s worth, you’ll find confirmation of this in Planet Muscle magazine (Volume 4, No. 4 2001) from the Vice President of marketing for a nutraceutical company. Nick Delgado, Ph.D., who is also President of the Asian Academy of Anti-aging and a former director of the Better Health Program at the Pritkin Longevity Center in California, says soy isoflavones don’t have a feminizing effect; to the contrary, he says they actually prevent estrogen from accumulating in the body by blocking estrogen receptors sites. According to Delgado, this can help both men and women reduce problems caused by having too much estrogen, which can include fat gain and loss of muscle. Delgado says he personally uses soy supplements and foods (tofu and soy milk) to guard against this problem.
Even if that's true, soy may still have a downside.
The Possible Dark Side
Dr. Weil’s best "guess" is that the benefits of soy outweigh the risks. Says Weil: "I believe that soy isoflavones can protect most people – men and women – from hormonally driven cancers as well as from coronary heart disease. They might even reduce the risk of osteoporosis."
As indicated earlier, Dr. Willett of Harvard Medical School worries about the effects of eating too much soy. "Two disconcerting reports suggest that in some situations soy protein could do more harm than good," he writes. "They point out the absolutely critical need to learn more about how soy protein affects different tissues at different stages of life."
In one study cited by Dr. Willett, women with a suspicious breast lump "showed substantially more cell growth and division" when given a soy supplement. "Animal studies also suggest reason for caution because soy estrogens promote the multiplication of breast cells in some circumstances but inhibit it in others. It’s not clear yet which applies to humans."
In another "troubling" study, older persons of Japanese ancestry living in Hawaii, who continued to eat the traditional soy-based diet were "more likely to have memory loss and other cognitive problems" than those who switched to a more Western diet. "This finding cannot be readily dismissed," says Dr. Willett, "because estrogens play a role in maintaining normal mental function, and it is possible that too much antiestrogen in the wrong place at the wrong time could be harmful."
"Similar uncertainties exist for prostate cancer," says Willett, "because higher estrogen levels appear to reduce risk. Whether soy estrogens mimic or block the effects of natural estrogen in the prostate is unclear."
What’s Dr. Willett’s bottom line? He agrees that soy is a good alternative to animal protein, that it may lower the risk of heart disease and have other beneficial effects. "Just don’t overdo it," he says. "Two to four servings a week of a soy-based foods such as tofu or soy milk is a good target."
Like Dr. Weil, Willett cautions against eating concentrated soy supplements or isoflavones pills. "One thing we know for certain about soy," he says, "is that the phytoestrogens it contains are potent biological agents. Whether they trigger, suppress, or have no effect on breast [and prostate] cancer is unfortunately an open question."
Dr. Willett’s call for moderation sounds like good advice. Mix your proteins and have soy every other day or so. Get some protein from a variety of the plant sources -- beans, nuts and soy -- and some from animal sources, such as nonfat milk or yogurt, fish, chicken and omega-3 enriched eggs.
If you have been diagnosed with cancer or have a family history of cancer, you should of course consult your doctor about using soy products in your diet.
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