best diet for pcos

Which 5 Foods Should You NOT Eat For PCOS?


What is the best diet for PCOS? This question is one of the most talked about PCOS topics. You’ll find it right up there with fertility and the pain of negative pregnancy tests. Visit any forum and you’ll find hundreds of posts asking what the best diet for PCOS is, which foods you should or shouldn’t be eating. You’ll even find threads dedicated to particular diets: slimming club, low GI, juicing, shakes, ketogenic, etc., etc.

The problem is that the majority of recommendations for the best diet for PCOS (even those given by dieticians and doctors) focus solely on calories and carbohydrates. Although calories and carbohydrates are not unimportant, arguably the more important factor to consider is how certain foods can induce inflammation.


The Best Diet for PCOS

Researchers have now found that PCOS is an inflammatory condition.

If you’d like to know more about inflammation then read my post about inflammation and PCOS. The main thing that you need to know is that certain foods are inflammatory and these are the ones that you should avoid.


Which Foods Are Inflammatory?

Before I get into this, I just want to make one thing very clear. What I’m providing here is not nutritional advice for the general population. This is specific advice for women with PCOS. It is often said that people should not cut out entire food groups. This is the case for normal people with normal metabolisms, but not women with PCOS.

Unfortunately, we (myself included here) don’t fit into the ‘normal’ category. Our metabolism is disrupted and we need to fix this by treating the root cause of the disruption. For the majority of us, this root cause is inflammation. Inflammation can be caused by many factors, but I’m going to focus on the foods that can cause it and the ones that I’d suggest you try removing from your diet.

Now don’t get me wrong, I’m not suggesting that any foods are ‘bad’ or ‘evil’. Instead, I’m merely detailing those that scientific research has proven can cause 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. These include grains (including gluten), and dairy.
– Food that has been processed in a way that makes it inflammatory. Examples include 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. Print it out and keep it handy.

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Which Five Foods Should You Avoid?

1. Grains

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

This is exactly what plants, such as wheat and other cereals, have done to protect themselves from predators. They have evolved to produce toxins to protect themselves. These toxins can damage the lining of our gut, inhibit digestion, and prevent absorption of essential nutrients, including protein.

The most common toxin in our diets is… Gluten

Gluten is in wheat and many other commonly eaten cereal grains, including barley. It can damage the intestine and make it leaky,  activating the inflammatory response.

Most people are aware of coeliac disease, which is caused by an allergy to gluten. However, very few are aware that many of us are affected by gluten, regardless of whether we are coeliac or not.

The main components of gluten that people with coeliac disease react to are: 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. Unfortunately, this isn’t routinely tested for by doctors.

Researchers now believe that 1 in 10 people have gluten sensitivity, but many aren’t aware of this. However, I (and other clinician’s treating PCOS) believe that up to 85% of women with PCOS may have non-coeliac gluten sensitivity.

There is very little research specifically on gluten intolerance and PCOS. However, studies have shown that removing gluten alone, while 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). If you can’t afford this test, then you might like to try removing grains entirely. Try it for at least 6 weeks to see if it helps your symptoms.

2. Dairy

When people think of dairy intolerance, they think about lactose sugar. However, 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 take milk from both A1 and A2 cows. As a result, the dairy products that we consume contain 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 to show whether you’re intolerant or not.

Again, while this doesn’t mean that everyone with PCOS is intolerant to A1 Casein, the fact is that PCOS is an inflammatory condition. This leads me to suggest that you try eliminating dairy for at least 3 months to see if your symptoms improve. Expect to see improvements in acne, weight, periods, and ovulation.

The following three food types aren’t inflammatory in their natural state. However, the the way they are processed (or how much of them we eat) means that they become inflammatory:

3. High Fructose Corn Syrup

Fructose is a type of sugar found in fruit and vegetables. The concentrations in fruit and vegetables are fine. But when it’s made into high-fructose corn syrup (HFCS) then it becomes an absolute disaster.

Studies have shown that HFCS increases inflammation, insulin resistance, and Non-Alcoholic-Fatty-Liver Disease. This is very interesting, considering that 60% of women with PCOS have fatty livers, compared with 24% of non-PCOS women. Whether this is a cause or an effect of PCOS is unclear. Nonetheless, I think it’s safe to say that it’s best to avoid HFCS at all costs.

High fructose corn syrup is found in many manufactured goods, including several unexpected ones. This includes low fat yoghurt, mayonnaise, sauces, and packaged soups. Make sure that you always check the labels!

 4. Seed Oils: Rice Bran, Canola, Soy, Corn and Sunflower

Yes, science has backtracked once again. These ‘heart healthy’ oils that you thought were safe might be contributing to your PCOS. These seed oils contain high amounts of the type of fat that causes inflammation: Omega 6 fat.

In their natural state, Omega 6’s are fine. For example, the Omega 6’s in sunflower seeds are okay, especially when eaten as part of a diet containing lots of fatty fish and other Omega 3 foods. Problems occur when the seeds are processed into oils, which are then used in a large amount of the food we eat. This results in consuming much more than we need.

Conversely, Omega 3 fats, contained in fatty fish and olive oil, reduce inflammation. Reducing inflammation will help to reduce PCOS symptoms. 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 a greater Omega 6: Omega 3 ratio is associated with all inflammatory diseases. This includes insulin resistance, Type 2 diabetes, and obesity.

Specifically, studies on PCOS have shown that higher levels of Omega 6 in the blood are correlated with higher testosterone levels.

You should be aiming for a 1:1 ratio of Omega 6: Omega 3. You may find this difficult, considering that most people consume a 10:1 ratio. Some people even consume as much as a 25:1 ratio of Omega 6: Omega 3. 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.

5. Processed Soy

Traditionally processed soy isn’t too bad for PCOS. However, the problem is that the majority of  soy we eat today is processed.

In Asia, soy is traditionally fermented and served as a condiment, such as miso, natto, soy sauce, or tempeh. They use a precipitation process to make tofu. This process removes some of the anti-nutrients from soy and then ferments the resulting product.

Modern soy foods are very different. The majority of them are made with soy protein isolate (SPI), a protein-rich powder extracted from the waste products of soy oil manufacturing. This industrial process strips the soy of much nutritional value and the resulting product contributes to inflammation.

Almost all packaged foods contain processed soy. You will see it on ingredients lists as Soy Protein Isolate (SPI), soy flour, soy lecithin, and soybean oil.

Processed soy also affects our nutrient status, as it increases our Vitamin D requirement. Studies have shown that 67-85% of women with PCOS have Vitamin D deficiency and that this deficiency may contribute to insulin resistance.

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

For the reasons I’ve outlined above, I suggest that you try removing processed soy and only consume small amounts of fermented soy. If you have a thyroid issue then you should try to avoid soy all together. There are alternatives available, such as Coconut Aminos which is a delicious alternative to soy sauce.

The best diet for PCOS may be different for everyone and I appreciate that this is a lot to take in.  To make things easier for you I’ve created a downloadable cheat sheet for you to print out and keep handy.

Click here to subscribe

Some more blogs you might be interested in

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  1. Hi, can you please explain the difference between insulin resistant carbohydrates and non insulin resistant carbohydrates? What are the best carbohydrates to eat for someone with PCOS trying to lose weight? Thanks

    1. Hi Jess, the best way to understand it is that sugar and sweeteners have no place for people with insulin resistance. Then focus on vegetable forms of carbohydrates.

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