4 Types to Eat & Which Ones to Avoid


Kym Campbell

By Kym Campbell, BSc. | Updated July 1st, 2023

Key Takeaways

Most soy and PCOS studies investigate soy-derived supplements. Data on soy foods is limited.

Soy supplements can be good for PCOS. But it’s unclear if this benefit translates to soy foods.

Fermented soy is the best type of soy for PCOS. Traditionally prepared, non-fermented, organic soy foods may be okay for some people.

All soy made from conventionally farmed soybeans should be avoided.

Soy has potential benefits for PCOS. But it can also cause harm. That’s because it depends on what you’re talking about when you say, “soy”.

During my free 30-Day PCOS Diet Challenge I include soy in my list of suspicious foods. When starting a PCOS diet, it’s best to exclude soy. When re-introducing it, you’ll still want to be selective of the products you choose.

To cover all the nuances of this important food, here’s everything you need to know about soy and PCOS.

Pros and Cons of Soy (According to Science)

You need to be skeptical of studies that show soy is good for PCOS. The goal is seldom to provide dietary guidance. But that doesn’t stop people from using it for that purpose.

Most research isolates one component of soy for study. They then give it to test patients in supplement form rather than have them consume soy whole foods. Soy isoflavones are the most well-studied. Soy isoflavones are also known as phytoestrogens. That’s because they have a similar structure to estrogen and have weak estrogenic effects [1].

Is soy good for PCOS? Some studies suggest that soy isoflavones are good for PCOS [2-7]. But others have found that it makes little to no difference or can cause PCOS symptoms [8-10]. One argument against soy for PCOS is that phytoestrogens can disrupt hormones [11, 12]. A recent review of the literature found, “no homogenous improvement” on hormones or fertility associated with soy and PCOS [13].

During my free 30-Day PCOS Diet Challenge and 10-Week Program, I err on the side of caution. If soy has the potential to disrupt hormones, then it’s best avoided. Even if the risk is low [14]. This makes the most sense during the first few months of switching to a PCOS diet. It’s better to re-introduce soy after your PCOS is back under control. You can then see how it affects you.

Some women, like Raynetta, find that cutting out soy can have a huge impact on their health.

The point of most studies looking at soy and PCOS is to develop soy-derived supplements [3, 4, 15]. They take a reductionist approach that isolates a single component of soy. This means they have limited value in providing dietary advice.

These studies can’t be used to determine if soy foods are good for PCOS or not. That’s because soybeans contain protein, fat, carbs, fiber, and many other micronutrients. They also have several other bioactive compounds besides isoflavones [13].

The key take home here is that any benefits or harms of soy isoflavones for PCOS, shouldn’t be conflated with soy foods. The over-emphasis on studies focusing on soy supplements also explains why the science is so confusing.

Summary

There’s evidence showing that soy isoflavones are good for PCOS. But they may also be harmful. The problem with most research is that it uses soy supplements rather than soy foods. This means it has limited value for guiding diet decisions.

4 Soy Foods to Eat

Based on the advice of trusted doctors, I have a negative bias toward soy and PCOS. But there’s a reasonable case for including certain soy foods in a PCOS diet. This is especially true if you’ve tried a soy-elimination diet first.

But which soy foods are okay for PCOS? Even though direct evidence on this question is lacking, we can let history guide us.

There’s compelling evidence that soy intake consistent with a traditional Japanese diet is healthy [16-19]. Fermented soy appears to provide the lion’s share of the health benefits of soy [20]. This may be why some large studies that look at soy consumption as a whole fail to find health benefits [21]. Several studies have found that only fermented soy is associated with a lower risk of heart disease [22, 23]. Others have shown that only fermented soy decreases the risk of some breast cancers [24].

With this in mind, fermented soy products are likely best for PCOS. This includes:

  1. Miso
  2. Natto
  3. Tempeh
  4. Tamari sauce

These foods contain live cultures of microorganisms that support better gut health. It’s believed that fermentation improves soy’s digestibility and absorption.

Summary

Miso, natto, tempeh, and tamari sauce are the best soy foods for PCOS. These are all fermented soy products.

Types of Soy on the Maybe-List

Tofu, edamame, and soy nuts are the few no-fermented soy foods that may be suitable for a PCOS diet. Again, that’s assuming you’re reintroducing them after having first eliminated soy for a period. Like many foods, this decision depends on your perception of the risks and benefits. The quality of the soy beans used though, should always be one of the most important considerations. You only want to buy organic products as explained further below.

To be clear here. I recommend that everyone taking part in my free 30-Day PCOS Diet Challenge avoid these soy foods to be on the safe side. The same goes for those doing my Beat PCOS 10-Week Program. I intentionally exclude non-fermented soy foods in my PCOS Meal Planner and in my free PCOS recipes. That’s because I want to maximize your probability of success.

Summary

For some people, organic sources of tofu, edamame, and soy nuts are the few nonfermented soy foods that may be suitable for a PCOS diet. These foods should only be reintroduced following a soy elimination diet.

Types of Soy Foods to Avoid

People with PCOS should avoid all soy foods made from conventionally-grown soybeans.

This includes but is not limited to:

  • Tofu, edamame, and soy nuts that aren’t organic
  • Soy milk and cheese
  • Soy protein powder
  • Meat alternatives
  • Soy snacks
  • Soybean oil

That means pretty much all processed foods with soy in them are out.

Summary

All soy foods made from conventionally-grown soybeans should be avoided by people with PCOS.

Why Conventionally-Grown Soy is Bad for PCOS

Conventionally-grown soybeans are bad for PCOS because over 90% are glyphosate-tolerant (GT). Glyphosate a.k.a. Roundup, is the most used herbicide in the world. GT soybeans started being grown in 1996, so this is a relatively new problem. They’ve become the dominant soybean crop because they simplify weed management. Growers can spray their crops with glyphosate as they grow and it only kills the weeds.

This is great for reducing operating costs. But it’s not good for the soybeans.

A 2014 study found that GT soybeans grown in Iowa contained high residues of glyphosate and its products of degradation. The average was 9 mg/kg compared to non-detectable levels in “normal” soybeans [25]. Levels in other major producing countries are many times higher [26].

To put this into context, the US maximum allowable level is 40 mg/kg. In Europe and Australia, the level is 20 mg/kg. But experts in the field have raised several concerns that these “safe limits” underestimate the real health risks [27-31]. This is a complex area to get into. But, notably, the “safe limits” set by regulators are not based only on human health. They’ve been adjusted upwards to facilitate more intensive glyphosate use by industry [30]. It’s also worth noting that the acceptable daily intake limits in the US are six times higher than those in Europe.

There are many reasons people with PCOS should be concerned about glyphosate residues in soy foods:

  1. The International Agency for Research on Cancer has classified glyphosate as “probably carcinogenic”.
  2. Glyphosate is an endocrine-disrupting chemical (EDC) [32, 33]. This means it can interfere with hormone systems. EDC exposure has been fingered as an underlying cause of PCOS [34, 35].
  3. Glyphosate can disrupt the human gut microbiome [36-38]. Imbalances in the gut microbiome are also closely linked to the underlying drivers of all PCOS symptoms [39-41].
  4. Glyphosate has been linked to decreased fertility, adverse birth outcomes, and developmental issues [32, 36, 42-49].

If you want to avoid glyphosate in soy, then you need to buy only organic products. These contain no glyphosate residues. Organic soybeans are also more nutritious [25].

Summary

Conventional soybean products are bad for PCOS because they contain high levels of glyphosate residues. Glyphosate can disrupt the gut microbiome. It’s an endocrine disruptor with known adverse effects on fertility and birth outcomes. Organic soybeans are a better choice because they contain no glyphosate residues.

The Bottom Line

Not all soy foods are equal. It’s over-simplistic to say that soy foods are good or bad for PCOS. Studies show that soy-derived supplements may be helpful for people with PCOS. But that’s quite different from eating soy foods.

Fermented soy products have the most scientific credibility in terms of their health benefits. Other traditional non-fermented foods like tofu and edamame may be okay following a soy elimination diet. This is a risk-based decision. But either way, you’ll want to make sure all your soy foods are organic.

What you don’t want is any soy foods made with conventionally-grown soybeans. These foods contain high levels of glyphosate residues, a known hazard for PCOS.

FAQ

Is soy okay for PCOS? Soy is one of several important foods to avoid for PCOS. But there’s some nuances to this position. Conventionally cultivated soybeans contain high levels of herbicide residues [25, 26]. These herbicides are endocrine disruptors [32, 33] which are a known health hazard for PCOS [34, 35]. But organic, fermented soy foods are likely to support good health in the PCOS population [20, 22-24]. Supplements containing soy isoflavones may be good for PCOS [2-7]. But this remains controversial [8-10, 13].

Should I avoid soy for PCOS? When switching to a PCOS diet, it’s best to cut out all soy foods for at least two months. When reintroducing soy, start with organic fermented soy foods only. Non-fermented, organic soy may be okay for some people. All soy products made from conventionally grown soybeans should be avoided.

Is too much soy bad for PCOS? Too much soy can be bad for PCOS for several reasons. Evidence suggests that the phytoestrogens in soy can disrupt hormones [11, 12]. Glyphosate residues found in conventionally grown soy foods are also a hazard for people with PCOS. Glyphosate is an endocrine disruptor [32, 33]. It can impact the gut microbiome [36-38]. It’s also been linked to decreased fertility, adverse birth outcomes, and developmental issues [32, 36, 42-49].

Ready to Take Action?

  • Join my free 30-Day PCOS Diet Challenge here. This is a unique program where you’ll receive weekly meal plans, shopping lists, and helpful video lessons. You’ll also be part of a motivated and inspiring community of like-minded women.
  • Download my free 3-Day PCOS Diet Meal Plan here. This is perfect for getting started if you aren’t ready to commit to 30 days.
  • Join my PCOS Monthly Meal Planning Service here. This service includes hundreds of PCOS recipes within a pre-populated, yet customizable meal plan. It’s designed to save you time and help you apply a PCOS diet.
  • Sign up for my Beat PCOS 10-Week Program. This is a comprehensive program that covers diet, PCOS-centric emotional eating, exercise, stress management, and much more. All within a support group environment. The 10-Week Program includes the same recipes and meal plan as my monthly meal planning service.

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References

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