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How these oils fuel inflammation and healthier swaps
There’s been growing concern about seed oils and their effect on our health. Once marketed as ‘heart-healthy alternatives’ to butter and animal fats, these oils are now under the spotlight for their links to inflammation, chronic disease and poor metabolic health.
If you’ve ever wondered why nutritionists and health experts are telling you to ditch seed oils, here’s a breakdown of what they are, why they’re harmful and which healthier fats you can use instead.
What are seed oils?
Seed oils are industrial oils extracted from the seeds of plants, typically using high heat and chemical solvents. Common examples include:
- Soybean oil
- Corn oil
- Sunflower oil
- Safflower oil
- Cottonseed oil
- Rapeseed (canola) oil
- Grapeseed oil
Where are seed oils found?
Seed oils are cheap to produce, have a long shelf life and are used heavily in processed foods, takeaways and restaurant cooking. One of the biggest problems with seed oils is that they’re almost impossible to avoid if you eat a standard Western diet.
They’re often hidden in:
- Packaged snacks and convenience foods – granola bars, protein bars, crisps, crackers, snack mixes, microwave popcorn.
- Fried foods – not just fast food, but also some frozen or pre-prepared fried items.
- Condiments and sauces including mayonnaise, ketchup and pasta sauces.
- Baking and dessert packets such as pancake, cake and brownie mixes.
- Margarine, non-dairy spreads and some nut butters – seed oils are added for stability, shelf life and to make them spreadable.
- Plant-based milks – some varieties include added seed oils to improve texture and make them creamier.
Why are seed oils bad for you?
High in omega-6 fatty acids
Seed oils are loaded with omega-6 polyunsaturated fatty acids (PUFAs). While small amounts of omega-6 are essential, our modern diet contains far too much, especially compared to omega-3 fatty acids (found in fish, flaxseeds, walnuts). The ideal omega-6 to omega-3 ratio is thought to be around 2:1, but today, many people consume closer to 20:1. This imbalance fuels chronic, low-grade inflammation in the body.
Oxidative stress and cellular damage
The extraction process for seed oils involves high heat, pressure and chemical solvents like hexane. These methods damage the delicate fats, making them prone to oxidation. When oils oxidise, they form harmful compounds such as aldehydes and lipid peroxides. Once consumed, these unstable molecules create free radicals in the body, which damage cells and tissues. Over time, this oxidative stress accelerates ageing and weakens blood vessel integrity.
Disruption of metabolic health
Research shows that seed oils can negatively affect how your body processes energy. A high intake of omega-6 fats can interfere with the balance needed to manage blood sugar, store fat and burn fuel efficiently. Instead of supporting steady energy, excess omega-6 may disrupt hormonal signalling and make it harder for cells to function optimally.
Negative effects on health
The knock-on effect of seed oil consumption is wide-reaching. By altering the structure of your cell membranes and fuelling inflammation, they can set the stage for many chronic issues. Seed oils have been linked to:
- Persistent inflammation (contributing to autoimmune conditions, arthritis, asthma, IBS)
- Heart and circulatory problems (high blood pressure, heart disease, strokes)
- Metabolic dysfunction (type 2 diabetes, obesity, fatty liver)
- Cognitive decline (memory loss, Alzheimer’s, dementia)
- Skin issues (eczema, acne, premature ageing)
What’s the alternative?
There are plenty of nourishing, natural fats that support your health instead of harming it. The following fats are more stable, less processed and provide essential nutrients.
Extra virgin olive oil
Rich in monounsaturated fats and antioxidants, olive oil is known to improve heart health, longevity and reduced inflammation. It’s best used for salad dressings, drizzling, or low to medium-heat cooking.
Coconut oil
Coconut oil is mostly saturated fat, which makes it very stable when heated. It’s ideal for baking, roasting, or adding to smoothies and desserts. It also contains medium-chain triglycerides (MCTs), which are easily converted into energy.
Avocado oil
Like olive oil, avocado oil is rich in monounsaturated fats and vitamin E. It has a higher smoke point, so it’s great for roasting, baking or light cooking, and can also be used cold for dressings and dips.
Cold-pressed flaxseed oil or walnut oil
Cold-pressed flaxseed and walnut oils are excellent for balancing omega-6 intake and boosting omega-3s. These oils are delicate, so they should be used cold (not heated) to preserve their structure. Try drizzling them over salads, steamed vegetables or adding to smoothies. Keep them refrigerated and use within a few weeks of opening to maintain freshness and prevent oxidation.
Tallow (in moderation)
Traditional fats like tallow are stable and nutrient-rich when sourced from healthy, grass-fed animals. Naturally rich in fat-soluble vitamins (A, D, E and K), tallow was a staple in traditional cooking long before industrial oils came on the scene. Because it’s highly stable, it doesn’t oxidise easily when heated, making it suitable for occasional use in roasting or slow cooking.
How to avoid exposure to seed oils
Even small amounts of seed oils can add up in the modern diet. Here are some practical ways to limit them:
- Choose whole foods: Eat fresh vegetables, fruits, nuts, seeds and whole grains by following the CNM Naturopathic Diet.
- Avoid processed and packaged foods as they contain hidden seed oils.
- Limit fried and fast foods: Most restaurant and takeaway fried food are cooked in seed oils. Opt for grilled and baked options when eating out.
- Make homemade dressings and sauces with olive oil, avocado oil or nut oils instead of store-bought versions.
- Check plant-based milks to avoid varieties with added oils, such as barista-style milks that use oils to make them creamier.
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