Good Seed, Bad Seed - Why Seed Oils are Bad.

You may have heard some bad press recently about seed oils. There has been concern that seed oils are unhealthy. Most recently, these have been linked to an increase in colorectal cancers, especially in young adults. This article will extract (no pun intended!) and sort through some of the information out there.

What are Seed Oils?

Pictured are a variety of seed oils and the seeds from which they came including sunflower, black sesame seeds, and safflower seeds.

Seed oils are plant-derived and processed from the seed, rather than the fruit, of a plant. The oil can be extracted either using high temperatures and pressure or by cold extraction, crushing the seeds. Seed oils themselves are very processed and refined and may be a blend of multiple oils. These oils usually have a relatively high smoke point, meaning they can be used for high-temperature cooking, such as peanut and sesame oils. 

Some of the most common seed oils include:

• Canola

• Corn

• Cottonseed

• Grapeseed

• Peanut

• Safflower

• Sesame

• Sunflower

Why are these Oils Bad?

Like all oils, seed oils provide dietary fats. These fats are a mixture of saturated and unsaturated fats. Each oil contains omega-3 and omega-6 fatty acids. These can raise cholesterol and lipid levels in the blood. Seed oils tend to have a higher omega-6 content, which can be inflammatory. Inflammation contributes to many diseases, including heart disease, type 2 diabetes, and arthritis. These oils can create inflammation in the gut, a factor in colon cancer development. There has been a surge in the rate of colorectal cancer in teens and young adults over the last decade, so this is a crucial topic of concern.

Seed oils are relatively inexpensive and thus are abundant in ultra-processed foods (UPFs), hence the problem. Our Western-style diet is full of UPFs, so these oils are pervasive if we consume these foods frequently. UPFs contain other unhealthy components such as sugar, salts, additives, artificial colors, and preservatives. Another issue is that many oils are not pure but a blend of multiple oils. 

What Oils Should Be Used?

Bottles of different oils, some of which are healthier than seed oils, such as avocado, walnut, and olive oils.

The issue is not simply the use of seed oils but the consumption of these oils in abundance. Anyone who consumes a lot of UPFs is at risk. The occasional use of seed oils in baking and sautéing, in other words, moderate use, is not harmful.

Healthier options for oils include

• Olive oil - extra-virgin, cold-pressed (refined versions have a higher smoke point)

• Avocado oil - this is great for high-temperature cooking

• Flaxseed oil - a good source of omega-3s, but not for cooking due to its low smoke point

• Walnut oil - used more as a finishing oil or for dressings since, like flaxseed oil, this one has a low smoke point

• Chia seed oil - yes, this is seed-derived, but full of omega-3 fatty acids and has a high smoke point

Look for pure oils, not blends.

Refined versus Unrefined Oils

A refined oil undergoes extraction through the use of high heat. This process may decrease the nutrient content of the oil. Oils that are unrefined or cold-pressed use a crushing method to extract the oil from the seed or fruit. These oils are more nutrient-dense than refined oils. Unrefined oils may have a shorter shelf-life, while refined oils are typically better for high-temperature cooking.

The Bottom Line

Photo of a variety of ultra-processed foods which are the greatest source of unhealthy oils.

The heaviest consumption of seed oils comes from eating ultra-processed foods, fast foods, and eating out. These increase saturated fat and omega-6 fatty acid intake, which can increase inflammation. Seed oils used occasionally, in moderation, are unlikely to be problematic. 

Reducing your intake of UPFs reduces many unhealthy dietary components - saturated fats, sugar, salt, artificial food dyes, sweeteners, additives, and preservatives. As always, read labels. Choose healthier options for the bulk of your cooking and reserve the others for some time use.