What You Really Need to Know About Eating Soy

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For decades, soy has gotten a free pass among health nuts, particularly vegetarians. Although every year the health-promoting myths associated with soy seem to grow, the research often paints a different story.

In just the last few decades, not only has the US become the top soybean producer in the world, it is now one of the largest consumers of soybean products. This is partly due to the food industry’s “ingenuity” in creating more ways to incorporate it into our food supply.

Fermented vs. Processed Soy

Many in the health food industry say that soy consumption is safe because it has been a large part of the Asian culture for thousands of years. But in reality, Asians have primarily eaten fermented soy foods—not the unfermented/processed soy products that flood our store shelves today.

Fermented soy products include natto, tamari, tempeh, soy sauce, pickled tofu, and miso. Fermenting neutralizes the toxins in soybeans and, in many cases, the entire soybean is used in the product. On the other hand, most of the processing techniques used today not only denature the proteins but also increase toxins.

The USDA reported in 2011 that 93 percent of the US soybean crop is genetically modified to be herbicide tolerant. This allows farmers to utilize specific herbicides for weed control that would have normally destroyed the crop. This just adds to the list of herbicides, pesticides, and fungicides available and used in their production.

Although the EPA has “acceptable limits” for the amount of residual chemicals the final crops can contain, being genetically modified only makes the herbicide use more prevalent.

Soy also naturally contains trypsin inhibitors that interfere with amino acid digestion and have been linked in some studies to pancreatic problems. In addition, soy is deficient in the amino acids cystine and methionine, two of the sulfur-containing proteins that are important for glutathione production. Also, the amino acid lysine in soy is somewhat fragile and is easily denatured during the high temperatures used in the processing of soy.

Like some other legumes, soy contains natural toxins as part of its defense system. Genetically modified soy tends to be higher than non-genetically modified soy.

During fermentation, however, many of the undesirable properties of soy are neutralized or negated. Fermentation deactivates trypsin inhibitors and other “anti-nutrients.” (Cooking reportedly also reduces trypsin inhibitors by as much as 90 percent.) Fermentation doesn’t automatically turn soy into the perfect food, but it greatly minimizes many of the problems associated with it.

Even so, fermented soy products shouldn’t be used as a main dietary component. Asians primarily use soy as a condiment, averaging a total of about 8 or 9 grams (less than two teaspoons) of soy protein a day—not as a replacement for animal protein as many Americans do.

Our own FDA continues to claim that 25 grams of soy protein a day is heart healthy. With all the foods that now contain soy, it accounts for up to 1/5 of the calories in the American diet.

Soybean oil is now the most widely used edible oil in the world. You’ll find soy protein products labeled as soy protein isolate, textured vegetable protein, hydrolyzed plant protein, or hydrolyzed vegetable protein. Soy protein is included in breads, cookies, donuts, cakes, pancakes, rolls, crackers, hot cereal mixes, soups, gravies, chili, as well as breakfast, energy, and other “health” bars. It is used to “fortify” pasta and meat. Soy protein is also the key ingredient in simulated meat products, including the famous vegetarian turkey replacement Tofurky. And we can’t forget about soy milk, which has about $1 billion in US sales each year.

Making Sense of Soy: What the Research Says

With soy so widespread, I’d like to provide a little clarity to the controversy that continues surrounding its use.

Clinical trials that have examined soy and its components more closely, and we’re starting to realize that eating too much unfermented (or processed) soy can be a problem.

Soy contains several isoflavones, which are active plant chemicals. Those in soy—phytoestrogens—are some of the best-known and most-researched chemicals because they are so similar to human estrogen.

Unfortunately, the studies on soy tend to be all over the map because of the varying types of soy available for consumption (raw, roasted, dry heated, fermented, defatted, genetically engineered, non-genetically engineered, extracts, isolates, etc.)

Regardless, much of the research on the effects of soy isoflavones indicates over-consumption may have a detrimental effect on the health of all people of all ages—women, men, and particularly babies.

Numerous soy isoflavone products and supplements are sold as a natural replacement for estrogen. Soymilk is often prescribed for the same reason—including reducing the incidence of hot flashes and other symptoms associated with menopause. Studies have shown that soy products help about 20–25 percent of women with these symptoms. If used for management of menopause, I would recommend sticking with fermented soy products. And if used on a regular, long-term basis, it’s a good idea to be monitored for development of endometrial hyperplasia, which can occur in some women.

It’s not just estrogen levels that decrease during menopause. The ovaries also produce progesterone, dehydroepiandrosterone (DHEA), and testosterone. Balancing these hormones and supporting the other glands that may need help, like the adrenals and thyroid, achieves better and more consistent results than just upping estrogen levels.

Other studies show that isolated isoflavones tend to activate estrogen receptors and trigger many of the same functions as excess estrogen would.

In young girls, higher estrogen levels bring about early puberty and heighten the risk of breast cancer later in life.

It has been well established that isolated soy compounds that mimic estrogen (particularly genistein) stimulate the growth of estrogen-dependent breast cancer in women. However, when the same amount of genistein is given as a complete soy food, it seems to have a protective effect against excess estrogens.

This perfectly illustrates how a whole food is more than the sum of its parts, and how the complex mixtures of bioactive compounds in whole foods interact with each other.

In men, isolated isoflavones from soy have been shown to decrease fertility and virility.

And one of the more dangerous (and downright scary) practices is the use of soy-based infant formula. Phytoestrogens can be very powerful, especially in infants, where even the smallest doses can influence tissues that are rapidly dividing and growing.

One study concluded that infants fed soy formula had blood levels of estrogen 13,000–20,000 times higher than infants fed either breast milk or formula made with cow’s milk. At these levels, based on body weight, the infants on soy formula were getting between six and 11 times the equivalent amount of estrogen that has been shown to have hormonal effects in adults.

Moreover, the isoflavones in soy inhibit the activity of the enzyme thyroid peroxidase, which is responsible for the production of the thyroid hormones T3 and T4. This can make things particularly difficult for those with hypothyroidism or who no longer have a thyroid. In fact, regular soy consumption may bring about hypothyroidism. I am of the firm belief that a very large segment of the population suffers from an underactive thyroid. Soy consumption is probably one contributing factor that we overlook.

Soybeans also happen to be very high in phytic acid, which tends to block absorption of certain minerals like calcium, iron, magnesium, and zinc. (The good news is that fermenting soy reduces phytic acid.)

My Recommendations

In the past, I’ve always felt that fermented soy products were fine in the diet and, in many cases, could actually improve health significantly. That has been proven explicitly with a fermented soy product like natto. It can be a godsend in the prevention and/or recurrence of cardiovascular problems.

I still think that fermented soy products are excellent and I continue to use them, just in moderation.

As for all the other processed soy products, I really don’t see any need for them to be included in a healthy diet. And I can say without any reservation or hesitation that soy has no place in infant formula.

Dr. David Williams

Meet Dr. David Williams

For more than 25 years, Dr. David Williams has traveled the world researching alternative therapies for our most common health problems—therapies that are inexpensive and easy to use, and therapies that treat the root cause of a problem rather than just its symptoms.

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