Soy and PCOS: Should You Avoid It?

I think you will agree with me when I say, researching about diet for PCOS can be confusing and overwhelming.

I am sure during your PCOS online search, you came across tons of foods said to be ‘good’ and ‘bad’ for PCOS.

One of these ‘bad’ for PCOS foods you may have come across is soy. Now, a question I frequently get asked is, “Should I avoid soy for PCOS?”

So in this post, I am going to answer this question. You will find out the benefits of soy for PCOS and any potential drawbacks. I will also tell you which soy products may be best for PCOS and which may be bad. Ultimately, you will learn whether you should avoid soy for PCOS.

Let’s get started.

Is Soy Bad For PCOS?

Soy does not have to be avoided if you have PCOS. Contrary to what you may have heard about soy for PCOS, it isn’t bad. But I understand why some women stop eating it. They hear soy acts like the hormone estrogen in the body and that they need to avoid it to reverse their PCOS. But, the estrogenic activity of soy is weak. So eating it will not impact a PCOS woman’s ability to balance her hormones.

But soy can also be a PCOS friendly food because it has been shown to lower insulin resistance and testosterone and improve fertility. But also reduce LDL cholesterol levels and oxidative stress.

What is Soy?

Soy products are made from soya beans (also known as soybeans). Soya beans are a type of legume native to East Asia but are now grown and consumed worldwide.

There are two main types of soy products, fermented and unfermented.

Fermented soy products include tempeh, soy sauce, miso and Nattō. They are made by combining soya beans with beneficial bacteria, yeast, mold or a combination of each and letting them ferment for a period of time. Fermentation gives soy products their flavor, aroma and texture. But also their health benefits.

Unfermented soy products include tofu, soy milk, soy protein isolate. Soy protein isolate is found in protein shakes and bars. This form of soy is highly processed because it has been stripped of its key nutrients like fiber.

Should PCOS Women Avoid Soy?

So, as I mentioned, many women are curious to know about soy and PCOS.

Here's the thing.

Despite soy being a popular food that is widely consumed, it is a very controversial food. Now, as is often the case in the nutrition realm, the information on soy for PCOS is conflicting. Opinions are divided among experts on whether it is good or bad for PCOS. Some experts praise soy for its health benefits while others claim it is bad for PCOS.

However, there is a lack of evidence into the effects of soy on PCOS are limited. So because of the lack of research and the controversial nature of this topic, this article will strictly be an evidence-based guide. This article will not be based on my opinion but instead on what the science shows.

The Benefits of Soy for PCOS

Soy Lowers Testosterone Levels

Women with PCOS produce too many male hormones. A study found soy can lower testosterone levels in women with PCOS.

Researchers looked at the effect taking soy isoflavones (50 and 100 mg/kg) would have on PCOS rats. The results show that after 14 days, there was a significant decrease in testosterone levels.

Now, we have to bear in mind it is an animal study, so results on humans may vary. But from the results, it appears adding soy to your PCOS diet may help lower testosterone levels. This may, as a result, improve PCOS symptoms.

Reduces Insulin Resistance

Insulin resistance is the most common root cause of PCOS. But researchers have found soy can improve insulin resistance in women with PCOS.
One of the studies that looked at the effect of soy on PCOS included a 12-week study. The researchers randomly allocated 70 PCOS women into two groups. One group took 50 mg/d soy isoflavones (a compound found in soybeans) and the other a placebo. The results showed the soy isoflavone group had lower insulin levels and their insulin sensitivity increased. Which means soy helped the cells in their body absorb the sugar in the blood more effectively.


May Improve Fertility

PCOS is one of the leading causes of infertility in women. You may have come across articles warning you against consuming soy for fertility. But researchers have found that eating soy may, in fact, help improve fertility.

A study found soy had a beneficial effect on women undergoing infertility treatment. Results show that IVF success rates were 77% higher in the group that consumed soy isoflavones (8–28mg/d) than for those who ate no soy products.

Watch Your Soy Intake

Now, with that said, researchers advise watching how much soy you eat. A study found eating over 100mg of soy isoflavones (the equivalent of 16 cups of soy milk or 6-ounces uncooked tempeh) daily increased the risk of infertility. Consuming that much soy on a daily basis does not seem possible if you are eating a balanced diet. With that said, experts suggest eating 1–2 servings of soy a day is safe.

Lowers LDL Cholesterol Levels

Research shows 70% of women with PCOS have high levels of LDL cholesterol, 'bad cholesterol', and low levels of HDL cholesterol, 'good cholesterol'. This combination puts women with PCOS at greater risk of heart disease. But research shows soy can reduce LDL cholesterol levels.

A study found participants who consumed on average 25g of soy protein per day, over a six week period, reduced LDL cholesterol levels by about 3-4%. This may sound like a small amount but it is still a significant and promising improvement. Experts suggest it is the high fiber content found in soy that helps to lower cholesterol levels.

Lowers Oxidative Stress

Women with PCOS have increased levels of oxidative stress. Meaning there is an imbalance of free radicals (cause the body harm) and antioxidants (protect the body). Many dietary, lifestyle and environmental factors (e.g. pollution) can cause oxidative stress.

But get this.

A study found eating soy can increase antioxidant levels and decrease harmful free radicals. So, soy may protect you from oxidative stress by increasing antioxidant levels.

Simply put...

All of the above benefits are incredible. The results show eating soy in moderation reduces insulin resistance, testosterone, LDL cholesterol levels, oxidative stress and improves fertility. Such results are highly encouraging for women with PCOS.

Risks of Consuming Soy for PCOS

Whilst there are some benefits to eating soy for PCOS. There are also some risks you must know if you are trying to balance your hormones and reverse PCOS.

Soy Impacts Thyroid Function

Researchers have found that up to 25% of women with PCOS have a thyroid condition. Unfortunately, problems with the thyroid are often missed in women with PCOS. This is why this type of PCOS is known as a ‘hidden cause’. Check out my ‘Types of PCOS: Ultimate Guide’ to find out more about the link between the thyroid and PCOS.

So here’s the thing.

Soy contains goitrogens, plant-based substances, that can interfere with thyroid function. They are found in foods like broccoli, kale, cauliflower, cabbage, spinach and strawberries. Experts state they inhibit the intake of iodine by the thyroid gland. The thyroid needs iodine because it helps to make thyroid hormones. But with that said studies have found little to no evidence that eating soy affects the functioning of the thyroid.

Researchers suggest that hypothyroid patients can eat soy as long as they have healthy iodine levels. But as always, consult your doctor before you change anything in your diet.

Soy is High in Phytic Acid

Soy is high in phytic acid. This substance inhibits the absorption of various minerals like iron, magnesium, manganese, zinc and calcium. As a result, soy is considered an ‘anti-nutrient’.

So here’s the thing.

Phytic acid can affect the mineral absorption of a single meal. But it does not impair all other meals eaten throughout the day.

So, for example

If you eat tofu for lunch, it could reduce the amount of minerals like calcium, iron and zinc you absorb. But it won't affect the meal you eat a few hours later.

Now, if you eat soy or other foods high in phytic acid with most of your meals, mineral deficiencies may develop over time. But this isn’t a huge concern if you follow a balanced diet.

How can I reduce the Phytic Acid in Plant Foods

While the impact on mineral absorption is low (if you eat a balanced diet), there are ways you can reduce phytic acid. According to research, there are three good ways to reduce phytic acid and they include

  1. Fermentation is said to be the most effective approach to reducing phytic acid. It is a process where live bacteria and yeast convert sugar into alcohol or organic acids. When fermenting soybeans, the organic acids formed from the process, promote the breakdown of phytic acid.
  2. Soaking. Research suggests soaking soya beans for 12 hours significantly reduces phytic acid.
  3. Sprouting. This involves soaking the soybeans then repeatedly rinsing them until they develop shoots (stems, leaves and buds). Research shows that sprouting increases the phytic acid degradation activity.


Most Soy is Genetically Modified (GMOs)

Genetically modified (GMO) soybeans contributed to 75% of the total global soy production in 2011. This is a process that involves changing the DNA of a plant in some way through genetic manipulation.

GMO soy plants have been produced to tolerate exposure to glyphosate (the world's most widely used weed killer). This is controversial because glyphosate has been linked to causing various chronic diseases.

Evidence shows organic soya beans, however, contained no chemical residues. They also showed the healthiest nutritional profile with significantly more total protein and zinc than GMO soy. So if you are going to eat soy, choose organic soy products.

What about Soy’s Impact on Estrogen?

As well as high male hormones, women with PCOS may have high estrogen levels. You may have come across articles warning you against eating soy because of its impact on estrogen levels.

The Claims

Articles suggest soy should be avoided because it is high in phytoestrogens. Phytoestrogens are naturally occurring compounds found in plants. The claims arise from the idea that phytoestrogens act like the body's natural estrogen. As a result, it is able to bind to the same receptors that our own estrogen does and in turn worsen PCOS symptoms.

What the Research says

So here’s the thing.

Experts say soy has estrogenic and antiestrogenic effects. This means the effect will vary based on your body’s current estrogen levels. So, it is suggested that soy may block the increase of estrogen in PCOS women who may have high levels. While women who have low levels of estrogen, soy may act more like the hormone and increase production.

But check this out.

Research suggests that while phytoestrogens can imitate estrogen in the body, they show weak estrogen activity. This is because they do not bind to estrogen receptors in the body as firmly as the body's real estrogen.

Soy and the Risk of Breast Cancer?

Following on from my point above. You may have come across articles claiming soy increases the risk of breast cancer. This is because soy contains phytoestrogens and cancers need estrogen to grow. Now, many studies have looked at the link between soy and breast cancer but the results don’t support the claims.

In fact, a study found eating soy may be associated with a reduced risk of breast cancer. But experts suggest this may be due to the type of soy products consumed.

Here's the thing.

The incidence of breast cancer in Asian countries compared to Western countries like the United State of America is much lower. Research shows the risk of breast cancer is 4-7 times higher in the United States than in Asia.

It is believed that tofu and miso, the two main types of soy products consumed in China and Japan, may reduce the risk of breast cancer by 20%. While Western countries consume processed soy like protein bars and shakes.

Now, while there is no clear evidence of harm, there is a need for further research to discover a safe intake.

So, you might be wondering.

Should Women With PCOS Avoid Soy?

In summary, you can eat soy if you have PCOS. Soy certainly has some great benefits for PCOS women. Including a decrease in insulin resistance, testosterone levels and an improvement in fertility. But also a decrease in LDL cholesterol levels and oxidative stress. As well as a possible decrease in the risk of breast cancer (but this is something that needs to be studied more).

Though soy can also have some drawbacks. Like thyroid issues, if insufficient iodine levels and mineral deficiencies due to the high phytic acid. But also the risk of consuming chemically sprayed soy products.

The Decision Lies with You

Ultimately, the decision of whether you should avoid soy is up to you. If you do decide to add or continue eating soy, know that just like with most things, it is all about moderation. But from the evidence, it can be seen that not all soy is created equally. Choosing mostly organic fermented soy like miso, tempeh and Nattō is best, not just for PCOS women, but for the population in general.

Fermented soy is best because the fermentation process reduces the level of phytic acid and may reduce the risk of breast cancer.

However, the ideal amount of soy to consume is still not clear yet, but experts suggest 1–2 servings of soy a day is safe.

Do I Consume Soy?

Personally, I do eat soy. In moderation, I include organic fermented soy products like soy sauce, miso and tempeh in my PCOS diet. I choose organic soy because of its better nutrient profile and it's free from chemicals.

Bottom Line

If you don't suffer from low iodine levels or breast cancer, it may be healthy and safe to add soy to your PCOS. But always consult a medical professional before you change your diet.

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Hey there! I am Despina Pavlou, founder of PCOS Oracle, certified personal trainer and corrective exercise specialist.  I want to share with you the diet and lifestyle changes I made to naturally reverse my PCOS and achieve hormonal balance. I believe using my holistic approach you too can take back control from PCOS.


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