5 reasons to rethink seed oils

You’ve probably heard us talk about seed oils before, and undoubtedly you’ve heard about them on social media. The seed oil debate is huge; and the main consensus in the health space now is that they are bad for your health. But do you truly know why? 

In 1961, the American Heart Association officially adopted Ancel Keys’ recommendation for people to replace saturated animal fats with polyunsaturated fats (primarily seed oils). Since then, the adoption of seed oils in restaurants and food manufacturing has coincided with a decline in the health of the population. So how exactly do seed oils impact your health and why does saturated fat have the opposite effect? 

1. Oxidation 

Seed oils such as sunflower, rapeseed (also known as canola), soybean, vegetable or corn oil are all rich in polyunsaturated fatty acids also known as PUFAs. These fatty acids contain bonds which make them prone to reacting with oxygen and causing oxidation. 

Free radicals and oxidative stress are closely linked to disease. Oxidative stress causes many processes in the body to become negatively affected. One example is how people with a high intake of seed oils or PUFAs are more prone to sunburn. Many people note that as they remove seed oils from their diet, their level of inflammation goes down and they can stay in the sun longer without burning. Oxidative stress is a huge killer in the modern age. Oxidised molecules begin to make up part of our human tissue and cell membranes, leading to local inflammation, which over time can lead to disease.

Animal fats, on the other hand, do not oxidise and are far more stable at high temperatures. It is no wonder, then, that real nature-made fat is best for us and more supportive to our bodies. If you want to read more on this, I highly recommend the book Deep Nutrition by Catherine Shanahan.

2. Thyroid function 

PUFAs suppress our thyroid function by interfering with the active thyroid hormone T3. And they can also stop the liver's conversion of stored T4 into active thyroid hormone T3.

Our thyroid is a core part of our health, and in the modern day many people are dealing with a sluggish thyroid or even hypothyroidism. An inability to lose fat, unexplainable weight gain, cold hands and feet, and constant fatigue are all signs that your thyroid is struggling.

Avoiding seed oils and limiting your consumption of high-PUFA whole foods such as nuts, nut butters and seeds can help your thyroid bounce back. Saturated fats such as coconut oil can even help the conversion of T4 to T3.

3. Gut health 

Anything that goes through harsh chemical processing is never going to be beneficial for our gut. It is becoming more clear that the prevalence of IBS and other gut health issues may be down to the sheer amount of seed oil consumed in the modern diet. The average person is consuming 3–5 tablespoons of seed oil per day without knowing it, mainly through processed food, 90% of which contains seed oil.

Heading back to oxidation: this is also happening in the gut, damaging the gut lining and contributing to the condition known as leaky gut. Seed oils have also been shown to lower beneficial butyrate-producing bacteria in the gut, as well as shifting the gut towards pathogens and overgrowths.

When we remove seed oils from our diet, we allow our gut to heal. Saturated fats such as coconut oil can improve our gut health, since coconut oil is antimicrobial and can help combat minor overgrowths and pathogens.

4. Harmful toxins 

If you have never looked into how seed oils are made, I encourage you to do so after reading this article. The vast amount of processing that goes into turning seeds into seed oil is frightening. Of course, when seeds are cold pressed this toxic processing is avoided, but as we touched on in point one, seed oils, whether cold pressed or not, are still high in PUFAs.

From bleaching and deodorising to the addition of hexane, the industrial processing of seed oils leaves them full of harmful compounds and toxins. Over time, and with constant consumption, this can lead to disease.

5. Impacts hormone health 

Due to the burden that seed oils place on both the gut and the liver, it is no wonder that they impact hormone health. Of course it isn’t the only factor, but it’s one of the biggest reasons that people are struggling with their hormones. 

The chronic inflammation caused by the presence of seed oils in the diet interferes with hormone signalling, and the main hormones that routinely get affected are testosterone and estrogen. Seed oils are also high in omega-6, and an imbalanced intake of omega-6 to omega-3 (omega-3 being found in saturated fats) can shift the body into a pro-inflammatory state. This pro-inflammatory state in turn disrupts hormone function.

Summary 

Seed oils were a solution to a problem that never existed. Seed oils were introduced to paper over harm caused by other parts of modern life that were actually doing the harm, like alcohol intake, sedentary living, environmental toxins and pharmaceutical drugs. Saturated fats are what we've always eaten and thrived on, and they took the blame when they were never the problem.

Now, seed oils won't kill you immediately - of course not. It's not about being neurotic, but instead reducing what is dragging your health down as much as you possibly can.

Returning to the fats that are actually healthy helps us regain our health. The wonders that people have seen from eradicating seed oils from their diet are a testament to this. We never needed seed oils; we just needed to return to how we've always lived, in line with nature.