Are Seed Oils Bad for You? New Research Reveals the Truth

For a while now, claims have been floating around the internet highlighting the ‘health risks’ of seed oils. Such oils include kitchen mainstays like rapeseed oil and sunflower oil (most vegetable oils are seed oils), which are generally rich in omega-6 polyunsaturated fatty acids.

Although omega-6 fatty acids are essential for the body, some critics have argued that elevated levels can lead to inflammation, which, in turn, can increase your risk of certain diseases, including heart disease, obesity, and cancer.

Why Do Some People Think Seed Oils Cause Inflammation?

The argument that seed oils can cause inflammation comes from the way they are metabolised in the body. Omega-6 fatty acids – particularly linoleic acid (found in seed oils) – are converted into arachidonic acid by our body. When the body needs to respond to an event, for example, an injury or infection, arachidonic acid is converted into a type of signalling molecule (a tiny chemical messenger), which may promote inflammation to help deal with the injury/infection.

It’s a normal immune response, but it could potentially be harmful if chronically elevated over time. Some researchers have argued that the issue lies in the ratio of omega-6s to omega-3s (which tend to produce anti-inflammatory compounds). In other words, if somebody is consuming too much omega-6 compared to omega-3 through their diet.

However, new research presented at the American Society for Nutrition’s recent annual meeting has challenged this school of thought entirely, suggesting that omega-6 fatty acids found in seed oils may reduce inflammation and support cardiometabolic health.

What Did the Study Find?

Based on a study of almost 1,900 people, the researchers found that higher levels of linoleic acid in blood plasma were associated with lower levels of biomarkers of cardiometabolic risk, including those related to inflammation.

While several observational studies have already shown higher intake of linoleic acid to be associated with lower risks for type 2 diabetes and cardiovascular events (like heart attacks and strokes), this new study employed more robust methods. Researchers used objective biomarkers rather than diet records or food frequency questionnaires to assess linoleic acid intake, making the results more reliable.

The researchers found that those with higher linoleic acid showed lower levels of glucose and insulin, as well as something called HOMA-IR, which is a biomarker of insulin resistance. They also had lower levels of inflammation biomarkers, including C-reactive protein, glycoprotein acetyls, and serum amyloid A.

In layman’s terms, ‘their blood tended to have a healthier overall risk profile for heart disease and diabetes,’ the researchers explain.

Butter or Oil – Which is Best?

These findings are supported by another recent large-scale study of 221,054 adults, which compared the effects of butter with plant-based oils. The study, published in JAMA Internal Medicine, found that higher butter intake was associated with increased total and cancer mortality. Conversely, higher intake of plant-based oils was associated with lower total, cancer, and cardiovascular disease mortality.

Those who ate the most butter had a 15% higher risk of dying during the study’s follow-up than those who had the least butter, while those who consumed the most plant oils had a 16% lower risk of dying during the study’s follow-up than those who consumed the least.

Based on further calculations, the researchers conclude that swapping 10g of butter per day with an equivalent amount of plant-based oils is linked to an estimated 17% reduction in total mortality and 17% reduction in cancer mortality.

The Bottom line

This isn’t to say you need to go on a butter rampage and rid your fridge of all the evidence. Certainly not when a tub of the good stuff is so pricey these days. No – it’s simply about moderation. It’s probably not a good idea to slather everything in oil either.

We know we say it all the time, but as long as you’re consuming something as part of a balanced diet, there’s likely very little risk involved. Perhaps if you have a lot of butter, it might be worth cutting down and using plant-based oils for cooking instead. However, as long as you are consuming butter and oil in moderation, you should be alright.

It’s more about challenging the messaging that something is inherently unhealthy. There’s almost always nuance involved.

Next time you see somebody slating seed oils, you’ll have the information and evidence to take their claims with more than a pinch of salt.