The Soy Ploy | Chris Kresser
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The Soy Ploy

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Today’s article about the dangers of soy products is from Nourishing Our Children, an organization dedicated to supported learning, behavior and health in children through optimal nutrition. I encourage all parents to visit their website and read the “What Parents Need to Know” section. There is also a downloads section with free guides and briefing books available for download.

Although widely promoted as a health food, hundreds of studies link modern processed soy to malnutrition, digestive problems, thyroid dysfunction, cognitive decline, reproductive disorders, immune system breakdown, and even heart disease and cancer.

How could soy be linked to all this disease? Because the soybean contains many naturally occurring toxins. All legumes contain toxins but the problem with soy is that the toxins are found in very high levels and are resistant to the traditional ways of getting rid of them.

Long, slow fermentation (as in the traditional production of miso, tempeh and soy sauce) gets rid of the phytic acid and other digestive inhibitors but not the phytoestrogens in soy.

Myths about Isoflavones

One of the most common myths is that soy estrogens (isoflavones) are beneficial for your health. Isoflavones are the estrogen-like compounds occurring naturally in soy foods. They act as the plant’s natural pesticides, causing insects to become sterile. Research has shown that isoflavones can prevent ovulation and stimulate the growth of cancer cells. As little as 38 mg isoflavones per day (less than the amount found in 1 cup of soy milk) can result in hypothyroidism with symptoms of lethargy, constipation, weight gain and fatigue. The isoflavones in soy have been shown to cause reproductive problems, infertility, thyroid disease and liver disease in mice, rats, cheetahs, sturgeon, quail, sheep, pigs and marmoset monkeys.

Traditional versus Modern Soy Foods

It is important to distinguish between traditional and modern soy foods. In Asia, traditional soy foods were consumed in small amounts, usually as a fermented condiment. Traditional fermented soy foods include miso, soy sauce, tempeh and natto. Tofu was prepared by a precipitation process that gets rid of some of the anti-nutrients, and tofu was often then fermented. Tofu was usually consumed in small amounts in fish broth, which provided lots of compensating minerals and compounds that support thyroid function.

Soymilk underwent a very long preparation process to get rid of anti-nutrients and it was consumed with shrimp or egg yolk, ingredients that helped compensate for the many anti-nutrients that remained. Mostly a food for the elderly, it was sometimes given to nursing mothers but never to growing children.

Problems with Soy Protein Isolate

Modern soy foods are very different. Most are made with soy protein isolate (SPI), which is a protein-rich powder extracted by an industrial process from the waste product of soy oil manufacturing. It is the industry’s way of making a profit on a waste product. The industry spent over 30 years and billions of dollars developing SPI.

Soy Protein Isolate is produced at very high temperatures and pressures. This processing does get rid of some of the anti-nutrients in soybeans, but unfortunately many of the proteins are denatured in the process, including lysine. That is why growing animals fed soy must be given a lysine supplement. In feeding studies, SPI caused many deficiencies in rats. That soy causes deficiencies in B12 and zinc is widely recognized; but the range of deficiencies was surprising.

Although SPI is added to many foods, it was never granted GRAS status, meaning “Generally Recognized as Safe”. The FDA only granted GRAS status to SPI for use as a binder in cardboard boxes. During the processing of soy, many additional toxins are formed, including nitrates (which are carcinogens) and a toxin called lysinoalanine. It was concerns about lysinoalanine in SPI that led the FDA to deny GRAS status for SPI as a food additive.

In spite of all these problems, SPI is the basic ingredient of soy infant formula and the FDA even allows a health claim for foods containing 6.25 grams SPI per serving.

The Dangers of Soy Infant Formula

Infants on soy formula can take in dangerously high levels of soy isoflavones. On a body weight basis, this can mean ten times the level that can cause thyroid suppression in adults after three months, and eight times the level that can cause hormonal changes in adults after just one month.

According to a Swiss report adult women consuming 100 mg isoflavones (about 2 cups of soy milk, or 1 cup of cooked mature soybeans) provide the estrogenic equivalent of a contraceptive pill.

This means for a baby that weighs 6 kg (or just over 13 pounds), 10 mg provides the estrogenic equivalent of a contraceptive pill. Thus, the average amount of soy-based formula taken in by a child provides the estrogenic equivalent of at least four birth control pills. Because babies are more vulnerable than adults to the effects of dietary estrogens, the effects could actually be much greater than that of four birth control pills.

Hence the statement, “Babies on soy formula receive the estrogenic equivalent of at least five birth control pills per day.”

Homemade Baby Formula

For adopted infants, or as a solution for mothers who aren’t physically able to breastfeed or who aren’t able to produce enough milk, we’d like parents to know that there are nutrient dense, homemade Baby Formula Recipes in the book Nourishing Traditions which have been used with great success by parents all over the world since 1995!

  1. Some of your other articles have a good quality, but this one is a shame. No source, no link for some research.

  2. are you not just telling your readers what they want to hear? After all meat and dairy eaters are by far your biggest target?

    • I think this articles is good example of fallacy of authority, while some of his articles are good, this one was weak.

    • His readers are not dairy eaters. It’s almost as if you’ve never investigated the Paleo diet at all.

  3. still herbivores have roamed the planet for more than 250m years. guess they avoided soya…or has soya just appeared n earth? fact is meat is unhealthy. dairy is unhealthy. causes dementia…yes.
    no food is perfect. soya is a LOT safer than meat and dairy

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