What 5 foods should you NOT eat for PCOS?


Diet and food is one of the most talked about topics in PCOS (right up there with fertility and the pain of negative pregnancy tests).  Go to any forum and you’ll find hundreds of posts asking what the best diet for PCOS is and what you should and shouldn’t be eating.  You’ll even find threads dedicated to particular diets: the slimming club thread, the low GI thread, the juice thread, the shake thread the ketogenic thread etc etc.

The problem is that a lot of recommendations around food, diet and PCOS (and even recommendations given by dieticians and doctors) focus solely on calories and carbohydrates.  While, I wouldn’t say calories and carbohydrates don’t matter, arguably the more important factor of how food is related to PCOS is how it can induce inflammation.

How is diet connected to PCOS?

Researchers have now shown that PCOS is an inflammatory condition.

I’ve written a whole post on inflammation, so I won’t repeat myself.  Instead I’ll explain to you how certain foods are inflammatory and what you should avoid.


What foods are inflammatory

Before I go into this, I just want to make one thing very clear.  What I’m providing here is not general population nutrition advice.  This is specific advice for women with PCOS.  You might notice my nutrition and dietetic colleagues saying that people should not cut out food groups entirely, and they are correct, for normal people with a normal metabolism.

But unfortunately, we (myself included here) with PCOS don’t fit in the ‘normal’ category.  Our metabolism is disrupted and we need to fix this by treating the root cause, which for many or us is Inflammation.  Inflammation can be caused by many factors.  Today I’m going to focus on the foods that can cause inflammation and what you might like to remove to see if it makes a difference for you.

Now don’t get me wrong, I’m not suggesting any foods are ‘bad’ or ‘evil’, merely these are what scientific research has proven causes inflammation for some people.

These foods fit into two categories:

  •  Foods that we might not be able to digest, either due to poor gut health or genetic predisposition:  Grains (including Gluten), and Dairy.
  • Food that has been processed in a way that makes it inflammatory: Processed Soy, High Fructose Corn Syrup and Seed Oils (Corn, Canola, Sunflower etc)

I’ve created a downloadable cheat sheet to make this easy for you to print out and keep handy.

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1. Remove Grains

Imagine if we had developed a toxin in our bodies that killed mosquitos when they bite us. Not only would al fresco summer evening be much more pleasant, but Zika virus wouldn’t stand a chance. We would have enhanced our survival rate.

This is exactly what plants like wheat and other cereals did to protect themselves from predators like us. They can’t flee like animals so they evolved to produce toxins that damage the lining of our gut, inhibit digestion, and absorption of other essential nutrients, including protein. All grains have developed a toxin, but the most common in our diet is gluten, which is present in wheat and many of the other most commonly eaten cereal grains, including barley. In some people Gluten damages the intestine making it leaky and activating the inflammatory response.

Most people are aware of coeliac disease caused by an allergy to gluten, but very few are aware that many of us are affected regardless of whether we are coeliac or not. Coeliac disease is diagnosed by a test that detects antibodies to two components of the gluten compound: alpha-gliadin, and transglutaminase. However, we now know that people react to the other parts of wheat and gluten as well.  This is called Non- Coeliac Gluten Sensitivity (and yes it’s a real thing).  Unfortunately, this isn’t routinely tested for my doctors so you probably won’t know if you’re intolerant or not.

Researchers now believe that 1 in 10 people have gluten sensitivity

But I and other clinician’s treating PCOS believe that this could be as high as 85% in women with PCOS.

While there is very little research specifically on gluten intolerance and PCOS, studies have shown that removing gluten alone, and not reducing calories or carbs, resulted in weight loss and better insulin sensitivity.

The test for non-coeliac gluten sensitivity isn’t widely available and is quite expensive (about $250 USD).  Unless you can get this test done to prove you aren’t sensitive, you might like to remove grains entirely, at least for a while and see if it helps your symptoms.


2. Remove dairy

When people think of dairy intolerance, they think about the sugar Lactose.  But actually, the biggest problem in PCOS is a protein called A1 casein.  Cows either have A1 or A2 casein.  Most companies that produce dairy products in the western world, including the UK and Europe, New Zealand, Australia the US and Canada take milk from both A1 and A2 cows and so the products that we consume include both.

Studies have shown that A1 casein causes some people’s immune system to produce inflammatory cytokines.

It’s not inflammatory for everyone, but unfortunately there isn’t a widely available test.

Again, while this doesn’t mean that everyone with PCOS is intolerant to A1 Casein, the fact that it is an inflammatory condition leads me to suggest eliminating dairy  (at least for 3 months) and seeing if your symptoms (especially acne, weight, periods, and ovulation) improve.




The following three foods aren’t inflammatory for us in their natural state, but because of the way they are processed (or how much of them we eat) have become inflammatory:


3. Remove High Fructose Corn Syrup

Fructose is a type of sugar found in fruit and vegetables. In those concentrations it’s fine, but when it’s made into high-fructose corn syrup (HFCS), it’s an absolute disaster.

Studies have shown that HFCS not only increases inflammation, but also insulin resistance and Non- Alcoholic Fatty- Liver Disease.

Studies have shown that 60% us with PCOS have Fatty liver compared with only 24% of other women.

Whether this is a cause or an effect of PCOS is unclear, but I think it’s safe to say it’s best to avoid it at all costs.

High fructose corn syrup is again found in many manufactured goods. Many of which you wouldn’t expect: low fat yoghurt, mayonnaise, sauces, and packaged soups.


 4. Stop using seed oils: Rice Bran, Canola, Soy, Corn and Sunflower

Yes, science has backtracked once again. These ‘heart healthy’ oils you thought were safe are actually part of what might be contributing to your PCOS. These oils all contain high amounts of the type of fat that causes inflammation, Omega 6 fats, which are found in plant sources, such as Canola, Soy, Corn, vegetable, and Sunflower seed oils.

Conversely, Omega 3 fats, contained in fatty fish and olive oil, reduce inflammation—and thus, PCOS—and from where we should be getting a lot of the fat in our diet.

Omega 6 Fats compete with Omega 3 Fats for enzymes, so it’s the ratio of Omega 3 to Omega 6 that’s really important.

Studies have shown that greater Omega 6: Omega 3 ratio is associated with all inflammatory diseases, including Insulin Resistance, Type 2 diabetes and Obesity

Specifically, studies on PCOS, have shown that higher Omega 6 in the blood is correlated to higher testosterone levels, which we all know, means worse PCOS symptoms

You should be aiming for a 1:1 ratio of Omega 3: Omega 6.  This is no small task considering that most of you will currently be consuming 10:1 and up to as high as 25:1.

The best way to achieve this 1:1 ratio is by removing all seed oils from your diet, and increasing the amount of fatty fish you are eating.

In their natural state in some sunflower seeds for example, Omega 6’s are fine, especially if we are eating a lot of fatty fish and other Omega 3 foods.  But when we process it into oil, and use it in manufactured products, fried foods and at almost all restaurants in the world, we can quickly get much more than we need.

5. Remove processed Soy

Again, traditionally processed soy, isn’t so bad for PCOS, it’s the way that we process a lot of the soy we are eating that’s the problem.

In Asia, soy was traditionally fermented and served as a condiment, such as miso, natto, soy sauce, and tempeh. Tofu was prepared by a precipitation process that removed some of the anti-nutrients, and was then often fermented. Modern soy foods are very different. Most are made with soy protein isolate (SPI), which is a protein-rich powder extracted by an industrial process from the waste product of soy oil manufacturing and contributes to inflammation.

Processed soy is in almost all packaged food as  Soy Protein Isolate (SPI), soy flour, soy lecithin, and soybean oil.

In addition to this, processed soy also affects our nutrient status. Processed soy increases our requirement for Vitamin D.  Studies have shown that 67-85% of women with PCOS have Vitamin D Deficiency, and Vitamin D deficiency possibly contributes to insulin resistance.

Soy isoflavones can also inactivate the enzyme needed to make Thyroid hormone leading to Hypothyroidism.  Thyroid issues are much more common in women with PCOS so this is something we also need to be careful about.

These are the reasons I suggest to my clients that they try removing processed soy and only consume small amounts of fermented soy.  If you have a thyroid issue, you may be best avoiding soy all together.  You can instead opt for Coconut Aminos which is a delicious alternative to soy sauce.

This is a lot to take in, so I’ve created a downloadable cheat sheet for you to print out and keep handy

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Some more blogs you might be interested in

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