Are Soy Products Safe During Pregnancy?

Understanding a few topics of debate around soy will help you be able to make the best decisions about consuming soy products while you are pregnant.


  1. Processed soy and whole soy products are very different when it comes to their nutritional value.
  2. Soy may block absorption of enzymes and minerals.
  3. Soy may contribute to endocrine disorders during pregnancy.


Nourishing Traditions: The Cookbook that Challenges Politically Correct Nutrition and the Diet Dictocrats


Soy has been marketed as one of the healthiest food in the new millennium.  But there is some debate over whether or not soy products are safe, especially during pregnancy.  Remember that there seems to be a substantial difference between processed food products like tofu, soy protein powders, and soy milk compared to fermented soy foods like miso, natto, and tempeh.  Below we will uncover some of the potential concern, always keeping in mind this premise:


If it has been proven successful for multiple generations, then it is more likely to be successful for our future generations too.


Many believe that soy has been instrumental in their personal health.  Switching to soy has helped some lose weight. Some have battled cancer and heart disease in coincidence with the addition of soy.  Soy has helped lessen the symptoms of menopause. Some just say they feel better since they’ve switched to soy. Though soy may aid many along their way toward health, some findings indicate that soy is not to be thought of as the pinnacle of health.    


Endocrine researcher and nutritional consultant Raymond Peat, PhD, calls it “odd that the soybean should be singled out” as the source of health in Japanese culture.  Peat is an expert on female hormones, and in his book, From PMS to Menopause: Female Hormones in Context, he attributes the menopausal health of the Japanese to other factors, not soy.  


Soy is No Longer on the Heart Healthy List

In a 2017 FDA press release, director of the FDA’s Center for Food Safety and Applied Nutrition, Susan Mayne, wrote, “We are proposing a rule to revoke a health claim for soy protein and heart disease.  For the first time, we have considered it necessary to propose a rule to revoke a health claim because numerous studies published since the claim was authorized in 1999 have presented inconsistent findings on the relationship between soy protein and heart disease.”


The story goes deeper, however.

Soy May Block Minerals and Enzymes

“More than half of the total phosphorus in soybeans is in the form of phytic acid…Because of its chelating power, phytic acid makes many essential minerals in soybeans or in diets unavailable for absorption and utilization for both human and domestic animals; thus phytic acid is known as an anti-nutritional factor,” according to Science Direct.  


Unfermented soy products contain a natural protein called phytic acid (phytates).  In The Crazy Makers: How the Food Industry is Destroying Our Brains and Harming Our Children, Carol Simontacchi, CCN, MS, reports that phytic acid is actually “classed as an anti-nutrient because it blocks the absorption of minerals, especially calcium, zinc, and magnesium.”  “All three minerals play a crucial role in brain health,” she says. Any food that blocks nutrients during pregnancy must be balanced by its positive effect for the developing baby.


Soy May Not Be a Good Source of Protein

According to the Journal of Biological Chemistry, “Several trypsin and chymotrypsin inhibitors have been identified as part of the protein composition of the soybean plant.”  Trypsin is a digestive enzyme that breaks down proteins in the small intestine, and a trypsin inhibitor “reduces the biological activity of trypsin.”  Hence, soy protein may “depress growth” and  “can lead to protein assimilation problems in those who consume unfermented soy products frequently.”


If soy blocks the digestion of proteins, vegetarians may have to adjust how they consume soy.  In Nourishing Traditions, Fallon and Enig suggest, “Soybeans must not be used like other legumes in soups and other dishes but only as fermented products like miso, natto, and tempeh.”


Soy protein powders are popular as basic ingredients in many health food products, like Luna Bars, Cliff Bars, GeniSoy, soy cheeses, and soy burgers.  Fallon and Enig explain, “These protein isolates are usually obtained by a high-temperature process that over-denatures the proteins to such an extent that they become virtually useless while increasing nitrates and other carcinogens.”  This could mean that the “complete amino acid profile” used to sell these vegetarian food products is potentially not providing what is being promised.


Soy May Cause Endocrine and Reproductive Disorders, especially in Pregnancy

According to a research review in Frontiers in Neuroendocrinology (FIN), soy “contains upwards of 100 or more phytoestrogens,” also termed, “dietary estrogens.”  The journal went on to discuss the increasing concern that “phytoestrogens may interfere with the organizational role of estrogen in the developing brain and reproductive system…Regardless of animal model used, manipulation of estrogen during specific critical windows of development throughout gestation and early infancy leads to a myriad of adverse health outcomes including malformations in the ovary, uterus, mammary gland and prostate, early puberty, reduced fertility, disrupted brain organization, and reproductive tract cancers.  These effects mirror some very disturbing public health trends in Western nations.”


For mothers who consume a fair amount of processed soy, the discovery in this study by FIN may be worth consideration: “infant boys born to vegetarian mothers had increased incidence of hypospadias (malformation of the male external genitalia) suggesting that dietary components (perhaps phytoestrogens) cross the placenta and cause adverse effects on the developing fetus” and that the “endocrine disrupting component” of phytoestrogens may be one reason for “the increase in reproductive and behavioral disorders.”


Dangers of Soy for Infants and Children

Two studies by University of Illinois food science and human nutrition professor, Sharon Donovan, show that the soy isoflavone, genistein, in amounts present in commercial soy infant formulas, may inhibit intestinal cell growth in babies.  The studies show that “intestinal cells basically stop proliferating.”  In The Crazy Makers, Simontacchi writes, “Infants on soy formula may receive the equivalent amount of estrogen that is found in five to ten birth control pills each day.”  She discusses how this is especially devastating for little boys whose first 6 months of testosterone production is responsible for most of his programming as a male.  She says that, for little boys, “soy formula can inhibit the testosterone from having its effect on the male programming and on the wiring in the brain.” Ingesting huge amounts of estrogen can also “wreak havoc with their emotionality” she says.


Simontacchi also worries that animal studies show “excessive estrogens lead to aggressiveness or problem behaviors, hyperactivity, precocious puberty in females, increases in certain reproductive cancers, increased breast or prostate cancers, reduced sperm count, retention of testes in the body cavity, malformation of the male genitalia, increased risks of enlarged prostate gland and increased risks of prostate cancer.”  In sum, she reports “the high content of estrogen in the soy based formula results in permanent damage to the reproductive system.”


Tip: Consume Soy in Small, Fermented Amounts

Many of us think that soy has been eaten as a staple for thousands of years when the reality is that it has probably only been eaten in small unprocessed quantities.  And even in small quantities, soy was fermented to make health benefits available. Fermentation of soy disarms the enzyme and mineral-blocking phytic acids and the enzyme-blocking inhibitors that cause cancer and depress growth.  Eating fermented soy, rather than processed tofu or soy powder, also makes the proteins more usable. “Even after being subjected to heat, fermented foods are more easily assimilated because they have been predigested by enzymes,” say Fallon and Enig. Next time you are grocery shopping, see if you you can find fermented miso, natto, and tempeh at your grocer!


“Those who wish to eat tofu would be wise to imitate the Japanese who eat small amounts of tofu in fish broth and not as a substitute for animal foods”

Fallon and Enig



Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed