Ask & Answer: Soy and PCOS. Is it okay?

by Becky Miller on May 10, 2013

Screen shot 2013 04 24 at 5.33.49 PM 150x150 Ask & Answer: Soy and PCOS. Is it okay?Soy and PCOS

In response to last month’s post about dairy and PCOS, I had a few questions in regards to soy and PCOS as a possible alternative. Particularly soy milk, but I’m going to address soy in all forms. In order to understand why and how soy affects PCOS, we will need to have an understanding of the process of ovulation and the menstrual cycle.

The Ovary/Hormone Roadmap

Ovarian function is mainly based on  two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH). The ovaries produce estrogen in the cells of the follicles growing in the ovaries, which signals the release of FSH and LH. Basically, estrogen ‘talks to’ LH and FSH. When you have low levels of estrogen because of fewer follicles growing on the ovaries (this is known as the ‘follicular phase’ of the menstrual cycle), FSH is released to encourage the growth of more follicles, hence the name, follicle stimulating hormone. The cells in these growing follicles then produce higher levels of estrogen, which stimulates the release of LH (this is known as the ‘luteal phase’ of the menstrual cycle). LH is responsible for signaling ovulation to occur. This is the hormone that is detected with over-the-counter ovulation predictor kits. After ovulation has occurred, the body then produces progesterone to support a possible pregnancy. If pregnancy doesn’t occur, the lining sheds and menses begins and the cycle takes place again.

How Is Birth Control Like Soy?

Birth control pills work by constantly suppressing the LH surge (which causes ovulation) with high levels of estrogen. With constant high levels of estrogen, the body never ‘thinks’ it needs to release LH, which would cause ovulation, therefore preventing pregnancy. Just like birth control pills expose women to high levels of estrogen, so does soy. Keep reading to find out how. 

Will Soy Affect My Fertility?

Soy products generally come in the form of either genistein and diadzein. These are the most common forms of isoflavones and flavonoids, found on soy milk. As mentioned above, chronic levels of estrogen diminishes fertility by blocking ovulation. Soy products contain phytoestrogens that are naturally occurring and are ‘estrogen like.’  (1) “Phytoestrogens exhibit estrogenic activity in both in vitro and in vivo assays. Phytoestrogens elicit gene expression changes in reproductive tissues, confirming that they are biologically active in a living system. The doses at which these effects occur are quite variable.”

There is enough data from studies that have been conducted to confirm  that, (1) “a soy-rich diet can exert enough estrogenic activity to have a biological effect in women.” It can be hypothesized that interfering with estrogen will effect ovulation and therefore PCOS. 

(1) “Excess estrogen stimulation, such as from excess soy consumption, of the uterus in a continuous manner can inhibit implantation, {preventing pregnancy.} It is therefore conceivable that interference or excess in any of this signaling can lead to subfertility or infertility.” Exposing our bodies to chronic high levels of estrogen can diminish fertility. Increased estrogen most likely results in reduced ovulation.

A Positive Benefit Of Soy, But Is It Worth It?

In a recent study (2), it was found that “Phytoestrogen supplementation (36 mg/daily) significantly reduced LH (p = 0.000), TG (p = 0.000), LDL (p = 0.000), DHEAS (p = 0.000) and testosterone (p = 0.000) levels.” Did you see that this recent study also indicated a reduction of LH? Remember, that is the hormone that signals ovulation to occur. Bad news for fertility.

In this same study it was also “suggested that diets containing soy-protein may provide favorable benefits in reducing LDL cholesterol and cardiovascular risks.” The findings of a study (3) completed specifically done on women with PCOS and soy came to this conclusion, “The possible advantages derived from the therapeutic use of phytoestrogens in PCOS are limited to improvement of the lipidic assessment.” To this I say, diet, exercise and lifestyle factors can do this and more for PCOS and don’t put a PCOS woman at increased risk of cancer or infertility like soy containing products do. You should decide which is more important to you.

How Much Soy Is Too Much?

Now that we’ve established that soy does in fact affect hormones, PCOS, ovulation and fertility, we will want to know if and how soy should be consumed. There are varying levels of soy in different products. It is important to know that traditional Asian foods that contain foods, such as miso and tempeh contain 16 mg of diadzen and 23 mg of genistein. Soy milk contains 28 mg of diadzen and 43 mg (100 g) of geinstein. Levels that have been found to be ‘safe’ or to not interfere in studies with ovulatory function range from 10-25 mg. Considering that a serving of soy milk contains 28 mg, it would be my recommendation that soy milk has no place in a PCOS diet. 

PCOS & Soy: The Bottom Line

The female reproductive system is comprised of a very delicate cycle of hormones that rely heavily on estrogen. That delicate system is further complicated with PCOS and any environmental and dietary factors that could compromise this balance should be addressed.

The feelings of PCOS ‘symptom relief’ that one might feel from consuming soy in a PCOS diet are associated with the estrogen dominance similar to that of birth control pills and the reduction of DHEAs and testosterone levels. I call this ‘masking the symptoms’ at best. 

There are other, safer ways to regulate DHEA’s and testosterone levels and to improve lipid panels in PCOS to consider before switching to soy containing products.

From the studies, we will find that there is room for caution of consuming soy in a PCOS diet, particularly if you are trying to conceive and experiencing infertility.



About Me 150x150 Ask & Answer: Soy and PCOS. Is it okay?Becky Miller is a health coach for women with PCOS. She loves being able to walk the PCOS path with each of you. To receive more of the latest PCOS tips, news and deals, check the box below. You’ll receive more PCOS packed information just like this, PLUS a FREE PCOS Kitchen Guide straight to your inbox. Won’t you journey with me?

Becky Miller, PCOS Health Coach

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{ 2 comments… read them below or add one }

Aletha Turner February 6, 2014 at 1:55 PM

Would love more information.


Becky Miller February 22, 2014 at 5:27 PM

Contact me at to learn how to get set up with a time to chat.


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