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Years ago, experts told us to avoid any fat source that is solid at room temperature because these fats are typically made of saturated varieties and may contribute to increased LDL cholesterol levels . Because of this advice, many of us instead leaned on oils as fat sources — regardless of the source. More recently, another shift has been made when selecting fat: Seed oils are now being called into question, with some deeming them as unhealthy or even “toxic.”
But are they really as bad for your health as some might lead you to believe? Or is the anti-seed-oil hype just another health trend that has been blown out of proportion?
What Are Seed Oils?
Just as the name implies, seed oils come from seeds — such as canola, safflower and sesame. Depending on whom you ask, vegetable oils (like soybean) may be classified as a seed oil, as well.
Seed or vegetable oils are typically extracted from the source using a chemical solvent, followed by a refinement process. These oils also can be processed by crushing the seeds, allowing the oil to collect.
As one would imagine, seed oils are a source of fat, made primarily of polyunsaturated fatty acids, or PUFAs. Sources of these fats are typically liquid at room temperature but turn solid when placed in a cold environment. Not all PUFA sources are seed oils, as “healthy fats” like olive oil contain these fats, as well, although not in as large of a proportion as many seed oils do.
Your body cannot make PUFAs, and therefore it relies on your diet to fuel it with this type of fat. And while PUFAs have been villainized on social media, expert panels like the American Heart Association state that polyunsaturated fats can have a beneficial effect on your heart when eaten in moderation and when used to replace saturated fat and trans fat in your diet.
Can’t Take the Heat?
Seed oils can be used in various ways, from an ingredient in salad dressing to a vessel for deep-frying. However, it’s important to note that not all of them perform the same when facing a heat source.
Certain oils, including sunflower, canola and grapeseed, have high smoke points, meaning they can be heated to a high temperature before it stops shimmering and starts smoking. Generally speaking, higher smoke-point oils are the best options for frying or other cooking methods that require high temperatures. But when these seed oils are heated beyond their smoke point, bonds in oils can form compounds that may be harmful to your health in various ways, including impaired energy metabolism.
When cooking with seed oils, it is important to make sure that you are not heating it beyond the smoke point to avoid the formation of these potentially harmful compounds. But enjoying seed oils that have not been heated to this extent does not appear to pose the same risk.
Seed Oils and Toxins
One of the concerns surrounding seed oils is that the process used to extract them relies on hexane, a compound that is found in many products, like cleaning agents and stain removers. Hexane has been widely used for oil extraction because of its easy oil recovery, narrow boiling point and excellent solubilizing ability.
What can be understandably jarring to many people is that chronic hexane exposure in large quantities is linked to adverse effects on the central nervous system and other aspects of our health. While some people are more at-risk for being exposed to hexane in large quantities, like people who work with this solvent who may inhale the fumes or touch it to their skin, people exposed to it via their seed oil do not appear to be nearly as vulnerable. In one study that analyzed the hexane content of 40 oils, including sunflower, corn and canola oils, all contained hexane levels that were lower than the European Union’s maximum residue limit .
The Final Verdict
Despite what many health and wellness influencers may suggest, including seed oils in an overall healthy diet doesn’t appear to be cause for concern — just be careful not to heat them beyond their smoke point. So you can breathe easy when adding canola oil to your baked goods or sesame oil to your salad dressing.