# Do soy products really lower testosterone?

**URL:** <https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817>\
**Category:** Factual Questions\
**Created:** [June 30, 2016, 6:52pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817 "2016-06-30T18:52:20Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![DudeManBro](https://avatars.discourse-cdn.com/v4/letter/d/b9bd4f/32.png) [@DudeManBro](https://boards.straightdope.com/u/DudeManBro)\
**Post date:** [June 30, 2016, 6:52pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817/1 "2016-06-30T18:52:20Z")

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So what’s the final word on this?

I’ve been craving this tofu/mushroom in soy sauce dish.

Will probably make it soon, but don’t want to lose my bro-gains.

Need answer kinda fast.

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**Author:** ![Ornery\_Bob](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@Ornery\_Bob](https://boards.straightdope.com/u/Ornery_Bob)\
**Post date:** [June 30, 2016, 7:06pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817/2 "2016-06-30T19:06:24Z")

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I don’t know of any real science on the soy issue, but I do know that your testosterone levels are managed by the hypothalamus/pituitary/testicular axis and any deviations from your body’s natural setpoint will be dealt with… largely through aromatase production. If your testosterone level drops, your aromatase production will slow down accordingly to bring it back up.

Thankfully, messing with your hormones isn’t easy.

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**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\
**Post date:** [June 30, 2016, 8:28pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817/3 "2016-06-30T20:28:29Z")

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I don’t know about testosterone, but [genistein](https://en.wikipedia.org/wiki/Genistein) is a [phytoestrogen](https://en.wikipedia.org/wiki/Phytoestrogens), making it seem like you have slightly higher levels of estrogen than natural. But in adult men, for normal dosages, this doesn’t appear to be an issue in any way, whereas it does have some protective effects against cancer (the Japanese, for example, have 2/3rds the rate of cancer as the US).

If you’re worried about infertility or something, I might note that there’s not a shortage of East Asian people in the world, and they eat a lot of soy.

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**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\
**Post date:** [June 30, 2016, 8:53pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817/4 "2016-06-30T20:53:40Z")

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[Research summary:](http://www.livestrong.com/article/240105-does-soy-milk-lower-testosterone/)

> [@](#):
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> Neither soy protein nor soy isoflavones had any effect on testosterone levels in adult men who consumed soy foods or products, reports an August 2010 article published in “Fertility and Sterility.” This article was a meta-analysis, which is a review of many studies on one subject. Since that time, however, two research studies have produced different findings. Men who performed heavy resistance exercises after supplementation with soy protein for 14 days developed decreased serum testosterone, according to a 2013 article published in the “Journal of the American College of Nutrition.” Another article reported that when male rats were exposed to soy isoflavones in the first three weeks of life, testosterone production increased, according to findings in the February 2014 article in “Biology of Reproduction.”

My personal guess is that the “soy lowers testosterone” concept is getting a lot of press nowadays mostly as an updated and scientificated version of the “real men don’t eat quiche” concept from a few decades ago.

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**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\
**Post date:** [July 1, 2016, 4:30pm UTC](https://boards.straightdope.com/t/do-soy-products-really-lower-testosterone/758817/5 "2016-07-01T16:30:58Z")

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> [@](#):
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> Men who performed heavy resistance exercises after supplementation with soy protein for 14 days developed decreased serum testosterone, according to a 2013 article published in the “Journal of the American College of Nutrition.”

A 14-day study involving a grand total of 10 men doesn’t impress me as conclusive evidence of anything. And the rat study counts for even less (one wonders if the rats were less inclined to do bodybuilding to impress their rodent womenfolk).

There’s an awful lot of nuttiness promulgated about soy foods (the Weston Price Foundation is a prime example). Claims about soy being “feminizing” have been kicking around a long time. Did you know that soy causes homosexuality? [Look out!](http://www.wnd.com/2006/12/39253/)

Personally I think soy is Satan’s Own Food, and it explains why the Asian population is in drastic decline (from all the rampant homosexuality, soy cancers etc. etc.).