Soy is in everything! Should it be in me?
Let’s talk about Soy and pregnancy.
Other than natural production of estrogen in our bodies, soy naturally produces estrogen-like hormones called phytoestrogen. Consumption of soy, introduces these phytoestrogens into our bodies and can act and bind to receptors like regular estrogen our bodies produce. Why should you care? Well, before, during and after pregnancy, a woman’s body goes through many hormone-sensitive periods that rely on a delicate balance in order to successfully provide the gift of life. Eating soy during any of these periods could upset this balance and produce harmful effects in the development of the baby.
Soy is in EVERYTHING
You may be reading this and wondering why it affects you because you may not eat tofu or meat substitutes. Unfortunately it affects everyone, because soy is in basically every processed thing we eat.
After a friend of my mine was diagnosed with a thyroid disorder, her doctor said she was no longer allowed to eat anything with soy in it. That meant no soybeans, soybean oil, soy sauce, tofu, nor edamame. Her doctor said that the phytoestrogens and isoflavones in soy would confuse her thyroid into thinking it has produced too much hormone and cause it to shut down. The thyroid is the powerhouse of your endocrine system because it regulates and produces hormones in your body.
So, I decided to help her find some soy-less products, but it has been difficult! I’ve found soy in whipped butter, granola bars, pasta, and chocolate.
If even a tiny bit could affect my friend’s thyroid so much, I believe it is necessary to understand the potential effects of these soy by-products in pregnant and lactating women.
Okay but what actually is phytoestrogen?
Let’s start from the beginning. The soy we eat comes from Soybean. Soybeans naturally have isoflavones, such as phytoestrogen hormones, that can disturb the equilibrium of the endocrine system. Whether the soy has been fermented or processed, it will contain the isoflavones. These isoflavones, specifically genistein, daidzein, and glycitein, are considered endocrine disruptors because they have similar structures to hormones, such as estrogen. This means they act the same and can bond with receptors in the place of estrogen.
In addition to their endocrine disrupting properties, Isoflavones can only have a positive effect on the body if they are converted into their “free” form. Isoflavones in their “free” form can only be found in fermented soy.
It is the fermentation process that converts the soy isoflavones into their “free” form, thus allowing the isoflavones to be more bioactive in the body and have a positive health effect ( Pierce, 2018). Positive health effects include isoflavones acting as antioxidants, cancer preventors, antimicrobials, free radical scavengers, metal chelators, and antibacterial agents (Roh, 2014).
Fermentation of soy also decreases other natural chemicals in soy such as, the phytates and saponins, which interfere with protein processing in the body. Examples of fermented soy are tempeh, miso, and some soy sauces.
The most common form we, in the United States, are exposed to soy is in its processed form. Processed soy is especially found in baby formulas and soymilk.
Processed and raw soy isoflavones haven’t been digested and converted into their free form, so they must be converted in the large intestine before they can be beneficial and therefore lack the many of the health benefits of fermented soy.
Dr. Joseph Mercola, an internationally renowned natural health physician breaks down the dangers of soy and its effects on women in general. He actually suggests keeping away from processed and raw soy even if you aren’t pregnant.
“ 95% of the soy grown domestically is genetically modified soy… even if you choose the 5% of organically modified soy, there are still concerns.” — Dr. Mercola
Though my article focuses on organic, or not-genetically modified soy, it is important to note that genetic modification (GM) of soy has another effects in humans. Dr. Mercola refers to a study done in rates where the effects of GM soy consumption two to 3 generations later. Unfortunately, there aren’t a significant number of studies to completely confirm or deny if these GM effects will show up in humans.
So how much of an effect does what I eat have on my baby?
A very broad review was done by Netting et al. (2014) to test whether or not maternal diet has an effect on disease development in children. They included 42 studies, covering over 11,000 cases together, focused on the effects of maternal diet. Unfortunately, they weren’t able to see any significant correlation of disease development in offspring. Since this was a very broad study, it is not surprising that there was no significant correlation. But, Weber et al. (2001) found, in humans and rats, that ingested phytoestrogens will cross the placenta and be introduced to the fetus.
Since these phytoestrogens can cross through the placenta, there was a concern on whether or not they could be seen in breast milk. Jochum et al. (2017) focused on the controlled ingestion of polyphenol-rich beverages, such as soy drinks and decaffeinated black tea, by nursing mothers. They tested the breast milk to see the effects on the composition of breast milk. They specifically looked at flavonoid concentration and total antioxidant capacity.
New mothers were given either 250 mL of a soy drink (12 mg isoflavones; n = 18), 300 mL decaffeinated black tea (67 mg catechins; n = 18), or 300 mL water (n = 8) for 6 days in addition to their regular diets. They found that the mothers drinking the soy drink showed an increase in the isoflavone content in their breast milk, but those drinking the black tea showed no flavonoids in their breast milk.
Jochum et al. (2017) concluded that consumption of soy drinks, on a daily basis by the nursing mother, can introduce a daily exposure of 9.6 nmol isoflavones in a 4-month-old breastfed infant.
Basically if you eat soy while pregnant, it could cross into your placenta and affect the baby, but eating soy while breastfeeding absolutely exposes the child to significant quantities of soy. Still, it is much better to breastfeed than to use commercial infant formulas because the commercial formulas have an even higher amount of soy phytoestrogens in them.
“Soy formula is very high in these phytoestrogen components and can have levels that are 20,000 times higher than birth control pills…. Clearly is a formula that I believe should be banned and barred from commercial sale.” — Dr. Mercola
What happens to my baby if he/she/they is exposed to soy?
The majority of this research is done on rats and mice to study these effects in a similar mammal without causing harm to humans. The animals are exposed to higher levels of the soy hormones in order to see an effect in a shorter amount of time.These results are still importance because the effects seen in animals can help us predict what could happen in humans.
First, let us understand what excess estrogen can do to a pregnancy and a fetus. In a study by Zimmermann et al. (1991), they found that the administration of estrogen to pregnant animals could cause congenital disabilities in offspring and detrimental effects to the pregnancy. A child with congenital disabilities or defects may experience health problems throughout its life. The detrimental effects on a pregnancy can range from decreased weight gain for pregnant animals to decreases in birth weight and the number of births in the litter. In some cases, fetus reabsorption and abortion have been reported.
Then in 2005, Tousen et al. looked directly at the effects of isoflavones, such as phytoestrogens, throughout the pregnancy and in the critical years after birth in rats. Because isoflavones are endocrine-disrupting chemicals, Tousen et al. (2005) hypothesized that isoflavones could negatively affect the development of reproductive organs in fetuses.
Maternal rats were given diets containing 0 and 0.5 g/kg of genistein, an isoflavone found in soy products such as tofu, from pregnancy day 5 to postnatal day 13. They looked at delivery, anogenital distance, reproductive organ weight, and body weight of the infants at birth. There were no significant effects or trends seen in either the mothers or the offspring. Even after continuous exposure following birth, the offspring continued to show no significant effects on reproductive health. Still, the authors agree that further studies are necessary due to the lack of substantial results found in this paper.
As stated in the study by Tousen et al. (2005), isoflavones are considered endocrine-disruptors, therefore, they can affect the development of the liver. Won et al. (2016) decided to try and understand these effects after learning that fetal programming of carcinogenesis was reported in offspring exposed to maternal diets containing soy protein isolate (SPI) or genistein.
They fed a low-isoflavone diet to female rats before mating and throughout their pregnancy and lactation period. While studying the male offspring of the rats, they observed an alteration in the hepatic gene expression of the offspring due to the low-isoflavone soy diet.
Even after pregnancy, soy can interfere with the lactation period due to the phytoestrogen and isoflavones introduced into the maternal system during that hormone sensitive period. Tsugami et al. (2017) studied the MEC of mice and the effect of direct isoflavone introduction on MEC ability to produce milk. They concluded that the isoflavones could influence the milk production ability of MECs through different interactions with prolactin/STAT5 signaling. This means that consumption of soy isoflavones can cause adverse effects on MEC milk production abilities.
In addition to the studies into the potential endocrine effects of soy, there is a potential for neurological impacts of phytoestrogens from soy because the endocrine system works with the nervous system to regulate the body’s processes.
Lephart et al. (2002) compiled a review of their studies surrounding this topic. The conclusion made was that consumption of dietary phytoestrogens, resulting in very high plasma isoflavone levels could significantly alter sexually dimorphic brain regions, anxiety, learning and memory in adults. If soy phytoestrogen can produce these effects in adults, the consideration of the effects on fetuses is essential primarily because they are still in a developmental stage.
Li et al. (2011) studied the effect of soy consumption of maternal thyroid functions during pregnancy. Questionnaires, on soy intake frequency from 505 women enrolled during early pregnancy by random sampling in Shenyang, China, were collected. Additionally, spot urine samples were analyzed for concentrations of two primary isoflavones (daidzein and genistein) and creatinine. Urinary daidzein and genistein levels were significantly higher in the women who frequently consumed soy compared with the others.
The researchers found no correlations between urinary isoflavone levels and serum FT(4) or TSH. This means that dietary soy consumption during early pregnancy is not associated with the development of thyroid dysfunction or autoimmunity in the children.
Aromatase is the enzyme responsible for estrogen synthesis and can be found in many tissues throughout the body. Weber et al. (2001), looked at the effect of soy phytoestrogens on the perinatal synthesis of estrogen after learning of their effects in rats.
While following these potential effects on perinatal development, it was found that dietary phytoestrogens do not alter brain aromatase during pregnancy/lactation or perinatal development.
Portman et al. (2016) saw a higher percentage of Asian children affected by Kawasaki Disease and believed that in addition to genetic sources there could be a dietary factor causing the increase in cases. Kawasaki disease is an inflammation of the lymph nodes and causes other repercussions. They decided to look at the effect of dietary soy isoflavone consumption through questionnaires for the mothers of Kawasaki affected children and the children themselves.
The questions focused on the soy consumption frequency of the mother through the mother’s pregnancy and lactation period and in the children through the two years before their diagnosis. Maternal surveys on soy intake during pregnancy and nursing showed no significant differences in isoflavone consumption between groups.
They did identify an increase in Kawasaki affected children in those children on high soy diets versus those children that didn’t consume soy in the years before their diagnosis. They also found that Asian children had the highest consumption of soy during these periods and believed that this correlated to the increased cases of Kawasaki’s seen in Asian children. Portman et al. (2016) concluded that this study proved maternal consumption of soy had no significant impact unlike that of early consumption of soy by children who later got diagnosed with Kawasaki’s disease. So, consumption of processed soy at a young age can lead to a development of Kawasaki’s disease in children.
Prior a study done by Chavarro et al. (2016), it was found that, in rodents, soy phytoestrogens can modify, or tame, the effects of BPA. To test this conclusion in humans, Chavarro et al. (2016) evaluated 239 women that were enrolled in the Environment and Reproductive Health (EARTH) Study and had gone through in vitro fertilization. The women were provided a questionnaire, and urine samples were collected prior to the oocyte retrieval.
They found that in women that consumed soy, the urinary BPA concentration was modified and there was a higher percentage of live birth rates than those women who didn’t consume soy. Since this was the first study looking at soy intake and effects of BPA concentrations in urine, further investigations into this topic are necessary to confirm these conclusions.
So is soy bad or no?
The take-home message is that there are many “ifs” still associated with processed soy that it is better to stay away from it if you can!
“ Most soy today because of the phytoestrogens and because they are genetically modified, they are terrible for you.” — Dr. Josh Axe
Though many of the direct effects have only been seen in rats or mice, these results show that too much processed soy can have an effect on your pregnancy. As for post-birth consumption of processed soy, we see that there is a direct path of exposure for your child through breastfeeding.
Still, breastfeeding is better than using commercial baby formulas because the most common brands are LOADED with soy and phytoestrogens. Another important advantage to breastfeeding is that you can control the amount of soy that you and your infant are exposed to. If you decrease your soy exposure, you will decrease the amount of soy your child is exposed to through your breastmilk.
In general, children with high exposures to processed soy from birth have shown some negative effects of soy, so limiting consumption of soy is the best policy. The best way for limiting exposure to processed soy is to pay attention to the ingredients lists on your processed foods. Though hard to find, there are soy-less products out there!
An even easier way to avoid processed soy is to cut out processed foods in general. Then you won’t have the worry about the effects it may have on your pregnancy or your newborn.
References
Chavarro, J. E., Mínguez-Alarcón, L., Chiu, Y., Gaskins, A. J., Souter, I., Williams, P. L., . . . Hauser, R. (2016). Soy Intake Modifies the Relation Between Urinary Bisphenol A Concentrations and Pregnancy Outcomes Among Women Undergoing Assisted Reproduction. The Journal of Clinical Endocrinology & Metabolism, 101(3), 1082–1090. doi:10.1210/jc.2015–3473
Jochum, F., Alteheld, B., Meinardus, P., Dahlinger, N., Nomayo, A., & Stehle, P. (2017). Mothers Consumption of Soy Drink But Not Black Tea Increases the Flavonoid Content of Term Breast Milk: A Pilot Randomized, Controlled Intervention Study. Annals of Nutrition and Metabolism, 70(2), 147–153. doi:10.1159/000471857
Lephart, E. D., West, T. W., Weber, K., Rhees, R. W., Setchell, K. D., Adlercreutz, H., & Lund, T. D. (2002). Neurobehavioral effects of dietary soy phytoestrogens. Neurotoxicology and Teratology, 24(1), 5–16. doi:10.1016/s0892–0362(01)00197–0
Li, J., Teng, X., Wang, W., Chen, Y., Yu, X., Wang, S., . . . Shan, Z. (2011). Effects of Dietary Soy Intake on Maternal Thyroid Functions and Serum Anti-Thyroperoxidase Antibody Level During Early Pregnancy. Journal of Medicinal Food, 14(5), 543–550. doi:10.1089/jmf.2010.1078
Netting, M. J., Middleton, P. F., & Makrides, M. (2014). Does maternal diet during pregnancy and lactation affect outcomes in offspring? A systematic review of food-based approaches. Nutrition, 30(11–12), 1225–1241. doi:10.1016/j.nut.2014.02.015
Pierce, R. (2018). Fermented Soy (Part 3) — Isoflavones, the Phytoestrogens Found in Soy. Retrieved March 13, 2018, from http://holistic-pharmacist.com/articles/fermented-soy-part-3-isoflavones-the-phytoestrogens-found-in-soy/
Portman, M. A., Navarro, S. L., Bruce, M. E., & Lampe, J. W. (2016). Soy isoflavone intake is associated with risk of Kawasaki disease. Nutrition Research, 36(8), 827–834. doi:10.1016/j.nutres.2016.04.002
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