Seed oils: Are they really bad for your health?

They’re in everything from your favourite salad dressing to processed and packaged snacks. But here’s the question: are these seed oils damaging to your health? Let’s dive into what’s really going on with seed oils, why they’re such a hot topic, and whether they deserve a place in your pantry or not.

What are seed oils?

Plant oils that are extracted from parts of the plant or seeds are recognised as vegetable and/or seed oils. These include canola, sunflower, safflower, soybean, rapeseed and grapeseed. These oils are classified as polyunsaturated fats but did you know that not all of these fats and oils are created equal? Let’s break it down. 

Omega-3 essential fatty acids 

Omega-3s are polyunsaturated fats that include alpha-Linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They are essential because they cannot be made by the body, and can only be obtained through our food or supplementation. Omega-3 fatty acids can be found in foods like salmon, mackerel, sardines, chia seeds, hemp seeds and walnuts. They are an essential part of the diet, and help support cardiovascular health, normal brain function, a healthy mood, and reduce inflammation. 

Omega-6 essential fatty acids 

Omega-6s are polyunsaturated fats that include linoleic acid (LA), arachidonic acid (ARA) and gamma linoleic (GLA). Omega-6 is considered beneficial in moderate amounts and is mainly found in nuts, seeds, eggs and seed oils. For optimal health, you want to aim for a balance of about 3 parts omega-6 fats to 1 part omega-3 fats (3:1). But in today’s Western diet, the ratio is more like 25:1. This means most people are over consuming omega-6s and not enough omega-3.  

What are the different types?

One reason why this ratio is much higher than it should is due to the popularity of seed oils found in high quantities in food processing and in processed foods. Seed oils are a rich source of omega-6 fatty acids. The most common seed oils you will see used in cooking and food processing are :

• Canola oil
• Sunflower oil
• Soybean oil
• Safflower oil
• Corn oil
• Cottonseed oil
• Grapeseed oil
• Rice bran oil
• Peanut oil

How are seed oils made?

Despite being of natural origin, many seed oil crops are genetically modified and processed which includes numerous steps of refinement that expose the product to chemicals, pesticides and unnatural compounds. For example, when canola oil is partially hydrogenated (a process which alters its chemical structure), it transforms into a solid fat known as trans fat.

Are they bad for your health?

Seed oils are extremely popular in food processing and can be found in high quantities in numerous processed food products – often the main ingredient! Over consumption of these oils may be linked to poor health: 

• Research has shown there is no safe consumption of trans fats: even in small amounts, these have been linked to calcification of the arteries and reduced cognitive ability.
• Most seed oils are heavily processed: including bleaching and deodorising and when foods of this nature are consumed in excess it can wreak havoc on the body’s organs and immune system. 
• Contributes to inflammation: when there’s an imbalance of omega-6/omega-3 ratio outside of 3:1. LA also stops DHA and EPA from entering into tissues, so a diet high in LA generally results in low omega-3 fatty acid status.
• Should be consumed minimally: as most seed oils are being used in the form of ultra processed foods, packaged foods, and fast foods.

Are there good substitutes?

The good news is that there are alternatives that you can use at home! Cold pressed extra virgin olive oil (EVOO) is made of mainly monounsaturated fatty acids, with minimal amounts of polyunsaturated fat (omega-3 and omega-6) and saturated fat. Due to this fatty acid profile, and high antioxidant level, the consumption of EVOO has also been shown to have positive effects on cardiovascular health, and lowering disease risk. Additionally, the high antioxidant content of the oil helps to stop its fatty acids from breaking down into harmful polar compounds, and therefore protects the naturally stable oil when heated.

Avocado oil contains a similar fat profile to EVOO (mainly monounsaturated fatty acids), proving to be associated with heart health benefits and anti-inflammatory effects. Like EVOO, it is minimally processed. Look for oils that are the closest to their natural state, such as cold pressed oil as this will mean refining and processing is a minimum.

Summary:

Our bodies rely on the right balance of fats to keep things running smoothly, like rebuilding cells and producing hormones. The key is choosing the right types of fats to give your body what it needs. Navigating the supermarket and avoiding processed, packaged foods can feel tricky, but here’s the takeaway: opting for wholefoods that naturally contain healthy fats will do wonders for your overall health. 

Related articles:

• Which oil is best for cooking with?
• Are you ultra-sure you know what ultra-processed food is?

Reviewed by Healthylife health experts November 2024