Another source of Soy that we may not be aware of comes from the use of Soy in animal feed. Some people allergic to soy have noted allergic reactions to eggs, dairy and meat from soy-fed animals. Not a lot of science supports the premise that soy feed is the culprit just yet, but four studies indicate phytoestrogens end up in egg yolks, and one shows their presence in chicken liver, heart, kidney and muscle meat.
Many people will look to the traditional Japanese diet stating that it is heavy in soy use and they are healthy people. The difference being that most of their soy consumption is through fermented soy such as Tempeh, Natto, and Miso. Their diets are also not predominantly soy but Vegetable and Fish.
The Science of Soy
Soybeans and soy foods contain a variety of bioactive components, including saponins, protease inhibitors, phytic acid, and isoflavones. Isoflavones belong to a class of compounds generally known as phytoestrogens, plant compounds that have estrogen-like structures. The dominant isoflavone in soy is genistein, with daidzein and glycitein composing the remainder.
Soy isoflavones are frequently referred to as weak estrogens, and depending upon the specific circumstance, they can act as agonists, partial agonists, or antagonists to endogenous estrogens (such as estradiol) and xenoestrogens (including phytoestrogens) at estrogen receptors. Their activity varies by tissue concentration, cell type, hormone receptor type, and stage of differentiation. In addition to their estrogen receptor activity, isoflavones may also interfere with steroid metabolism by inhibiting aromatase, hydroxysteroid dehydrogenase, and steroid α-reductase, and by altering the ratio of estradiol metabolites. Soy isoflavones may also act as antioxidants; inhibitors of proteases, tyrosine kinases, and topoisomerases; inducers of Phase I and/or Phase II enzymes such as cytochrome P450s, glutathione S-transferase, and quinone reductase; and inhibitors of angiogenesis.
How is Soy potentially harmful to our bodies?
- High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.
- Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals soy containing trypsin inhibitors caused stunted growth.
- Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.
- Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimmune thyroid disease.
- Vitamin B12 analogs in soy are not absorbed and actually increase the body's requirement for B12.
- Soy foods increase the body's requirement for vitamin D.
- Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein.
- Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.
- Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing and additional amounts are added to many soy foods.
- Soy foods contain high levels of aluminum which is toxic to the nervous system and the kidneys.
A study at the Harvard Public School of Health in 2008 found that men who consumed the equivalent of one cup of soy milk per day had a 50% lower sperm count than men who didn’t eat soy. That is not including the other forms of soy that are most likely being consumed by this person.
In 1992, the Swiss Health Service estimated that women consuming the equivalent of two cups of soy milk per day provides the estrogenic equivalent of one birth control pill. That means women eating cereal with soy milk and drinking a soy latte each day are effectively getting the same estrogen effect as if they were taking a birth control pill.
Concerns about the dominant isoflavone Genistein’s effects on reproduction and development are due in part to extensive research in mice. Newbold believes caution is warranted, because her studies, as well as others, have shown that Genistein has such effects as inducing uterine adenocarcinoma in mice and premature puberty in rats. A recent study led by biologist Wendy Jefferson in Newbold’s laboratory and published in the October 2005 issue of Biology of Reproduction linked Genistein with effects such as abnormal estrous cycle, altered ovarian function, and infertility in mice.
Soy in Infant Formula:
This effect is even more dramatic in infants fed soy formula. The key ingredient in soy formula is soy protein isolate, a controversial compound that is not even recognized as safe for human consumption by the FDA.
Infants fed soy receive 6.25 mg of soy isoflavones per kilogram of body weight per day. This is more than 10 times the amount of soy isoflavones that has been shown to cause problems in adults. In a baby that weighs 13 pounds, 10 mg of soy provides the estrogenic equivalent of a birth control pill. The average amount of soy formula given to an infant in a day contains 40 mg of soy. This means that feeding soy formula to a baby is the equivalent of giving her 4 birth control pills.
This explains why babies fed soy-based formula have 13,000 to 22,000 times more estrogen compounds in their blood than babies fed milk-based formula.
The following chart summarizes 6 studies that have examined the effect of soy formula on infants. As you can see, the results clearly indicate that soy formula can not only cause problems during infancy, but can even predispose that baby to serious health problems later in life.
infant feeding. Isomil, Carnation Alsoy, Similac Neocare and Enfalac Prosobee all tested positive for GM soy, although suppliers did not know the products contained GM soy . All soy-based infant formulas sold in Canada are manufactured with GM soybeans and are unlabelled as such
While this post is for the most part anti-soy use, it is of course a huge topic up for debate in our culture, and one like any dietary choices that must be made on a personal level. As discussed there are many layers of concern, first with the chemical components of Soy and how this effects our bodies and secondly with the manipulation of the natural product of Soy, through genetic modification and contamination. Consumption amounts of this product are relatively high, perhaps higher than they should naturally be. As with many things in life, with moderation seems to be a good rule of thumb. Sadly in the American diet there is no moderation occurring in terms of soy. It is being consumed at alarmingly high levels, all we can do is understand the potential threats and choose accordingly how best to feed ourselves and our children.
As a Midwife I find it concerning the growing number of fertility issues I encounter with clients. The amount of autoimmune disorders, particularly with the Thyroid and Adrenal glands. In my experience personally and professionally, I find soy to be more potentially harmful than helpful to the vast majority of people.