One of my patient’s doctors recently told her to not give her girls soy because it could cause early onset of puberty. The foundation for this belief is that soy is an estrogen and that, as such, it would initiate early pubescence. Soy alarmists try their best to “make up” arguments that support their assertion that the molecules which resemble estrogen in soy are causing early puberty. They have no choice other than to take this position because if soy were really a potentially deadly estrogen as they suggest, it would have to have estrogen effects. The problem is that the studies do not support this assumption. And, as I will outline in this article, logic doesn’t support soy as the cause of early puberty in children.

First, here are a few studies that do not support the claim that soy is causing early puberty.

Study: Effects of chronic exposure to soy meal containing diet or soy derived isoflavones supplement on semen production and reproductive system of male rabbits. Anim Reprod Sci. 2007 Feb;97(3-4):237-45.

Conclusion: We conclude that chronic dietary treatment with soy based diet or soy isoflavones have no adverse effects on the observed reproductive patterns of male rabbits.

Study: Infant feeding with soy formula milk: effects on puberty progression, reproductive function and testicular cell numbers in marmoset monkeys in adulthood. Hum Reprod. 2006 Apr;21(4):896-904.

Conclusion: Infant feeding with soy formula milk has no gross adverse reproductive effects in male marmosets…

Study: Urinary sex steroid excretion levels during a soy intervention among young girls: a pilot study. Cancer Research Center of Hawaii, Honolulu

Conclusion: Soy intake did not cause any statistically significant increases in estrogen or any other sex hormone in young girls.

Study: Soy-based formulas and phyto-estrogens: a safety profile. Dipartimento di Biomedicina dell'Eta Evolutiva, University of Bari, Italy.

Conclusion: The safety of isoflavones in infant formulas has been questioned recently owing to reports of possible hormonal effects. Infants fed soy formula receive high levels of phyto-oestrogens in the form of isoflavones (genistein, daidzein and their glycosides). To date, no adverse effects of short- or long-term use of soy proteins have been observed in humans and exposure to soy-based infant formulas does not appear to lead to different reproductive outcomes than exposure to cow milk formulas.

The bottom line is that the scientific literature, as a whole, does not support the assumption that soy causes early pubescence. On top of this, neither does simple logic.

There is no indication that there is a difference in the early onset of puberty when we compare poor people to wealthy people. The reason why this is relevant is that the consumption of soy is very different amongst these two different groups. The question is whether poorer people eat any appreciable amount of soy.

When is the last time you heard someone with a limited income order a double soy whatever latte at Starbucks? And, soy is most certainly not one of the main food groups eaten in the poor community. In fact, I have recently asked many of my lower income patients how much soy they eat. The answer was overwhelmingly very little, if any at all.

The “soy-craze” is mostly a part of upper-middle to the wealthy class in America. I would love to see someone give a redneck a tofu-soy burger. (Politically incorrect term, I know.) The bottom line is that the people who make up the vast majority of the population eat very little to no soy.

Now, there will be those who say that they have read that up to 60% of the products on the market now contain soy. So, everyone is being exposed. Although I highly doubt the accuracy of this number, the important aspect isn’t that people are eating soy. The important aspect is the content of the phytoestrogens in the soy that is in question. The unfortunate reality for their argument is that most of the soy products on the market contain very little phytoestrogens due to the way in which they are processed.

The logic of the argument that soy is a major cause of early pubescence falls short when you acknowledge that the MAJORITY of Americans eat very little soy phytoestrogens. If the claim were true, we would see a drastic increase in early puberty amongst the wealthiest in our society. There is no indication that this is occurring.

So, is soy consumption causing early puberty in our children? Neither the science nor logic supports this assumption. Anyone who says this is spinning tales.