The messaging around seed oils has gotten really loud lately ~ specifically, the fact that are all bad for your health and should be avoided entirely. As an herbalist with 15+ years in the wellness space, I've seen a lot of natural ingredients demonized (and others overhyped) without proper context or nuance.
Humans have been consuming oily seeds & seed oils for thousands of years, and many of them are rich in nutrients that our body needs for proper function. However, pressed & unrefined seed oils are not the same as modern industrially produced & refined seed oils. How a seed was grown, what method was used for extraction, whether it is refined, and in what context it's used make a world of difference.
Extraction Methods: Pressed vs. Petrochemical
The traditional method of oil extraction applies lots of mechanical pressure to fatty seeds to separate the oil from the seed fiber. Cold pressing maintains a specific temperature during pressing for more heat-sensitive oils, while expeller pressing utilizes the heat that's generated ~ the process is otherwise essentially the same between the two methods.
Many seed oils are still produced by pressing, specifically to make culinary oils or carrier oils for whole packaged foods, health & beauty products. Our locally made Sunflower oil is cold pressed, while our local Macadamia oil is expeller pressed ~ the small amount of heat that's generated helps keep the oil flowing through the press.
On the other hand, seed oils that are destined for use in processed or fast foods utilize solvent extraction for higher oil yields. The solvent is usually hexane, a petrochemical, and these mass-produced oils are often derived from GMO seeds in the US. Herbicide residues like glyphosate are therefore much more common, since these plants have been bred to withstand high amounts of spraying.
Corn, Soybean, Cottonseed & Canola are almost exclusively produced by solvent extraction with hexane from GMO crops, and therefore these are some of the worst seed oils for your health.
Processing: Unrefined vs. Refined
The second major difference is whether the oil is unrefined or refined. Unrefined oils are simply filtered to remove debris, and therefore retain their unique color, flavor & aroma profile. This also means that their key nutrients are intact, including monounsaturated fatty acids (or MUFA), polyunsaturated fatty acids (or PUFA), and saturated fats, as well as antioxidants like vitamin E & polyphenols.
Refined (RBD) oils, on the other hand, are often bleached and deodorized using heat & chemical processing. They have essentially been stripped of their inherent color, flavor & aroma, so that they don't impart any of their qualities into the final product and have a longer shelf life. But by removing these unique properties, the nutritive benefits of the oils have also been taken away.
Dietary Context
How seed oils are used is also a major factor in their impact on your health. When subjected to intense heat, such as from deep frying in fast food, they can form inflammatory oxidized lipids. And because industrial seed oils are often found in high calorie, low nutrient density processed foods, they can contribute to systemic inflammation and oxidative stress in the context of an unhealthy diet.
The Omega 6 Debate
Omega-6, or linoleic acid, is often blamed to cause inflammation, but it's not inherently bad. It's actually an essential nutrient required for many key functions, including acute inflammatory responses like fever, swelling & blood clotting. In a diet rich with whole foods and natural sources of omega-3 (alpha-linolenic acid), the ratio of 3:6 remains balanced and omega-6 stays at a healthy level.
But for highly inflammatory diets full of processed foods and not enough omega-3, the ratio of 3:6 becomes imbalanced. In this case, an overconsumption of omega-6 long term can contribute to chronic inflammation and become problematic.
If you're making healthy dietary choices on a regular basis, you should not be concerned about including pressed, unrefined oils in your diet. In fact, both the seeds & oils of Flax, Chia, Hemp, Walnuts & Pumpkin seeds all provide omega-3!
Seed Oils to Avoid: Canola, Soy, Cottonseed & Corn
Canola or Rapeseed, Soy, Cottonseed & Corn oils are almost exclusively industrially produced from GMO seeds for glyphosate tolerance, extracted with petrochemicals, and further refined. Do not purchase them to use in your cooking (or body care), and avoid when possible. They may be hiding in a bottle labeled as 'vegetable oil' at the grocery store.
Seed Oils We Love: Sesame, Hemp, Flax, Pumpkin
There are many different seed oils that are cold pressed or expeller pressed and available unrefined ~ Sesame, Hemp, Flax & Pumpkin are just a few that provide health benefits in both culinary & body care applications. All four of these oils have a history of traditional use, are rich in essential fatty acids & antioxidants, and also support skin health when applied topically.
This list of 'good' seed oils is not exhaustive ~ Pomegranate, Rosehip, Chia & Raspberry, are all examples of therapeutic seed oils primarily found in skin care that provide diverse benefits. Remember that unrefined oils will always provide more nutrients than their refined counterparts, so keep that in mind when purchasing any of the oils listed above.
Seed Oils with Nuance: Sunflower, Safflower, Grapeseed
Sunflower, Safflower & Grapeseed are three oils with extra nuance ~ they can be produced either by pressing or by solvent extraction, and are available as unrefined or refined oils. In general, solvent extraction is used for industrial & mass produced applications, while pressed versions of these oils can be found bottled as culinary oils, in natural packaged foods & body care products.
In general, even the industrially produced versions of these oils are still a better option than corn, soy & canola in processed foods because they are non-GMO, and therefore have less herbicide residues in the final product.
If you're buying these oils to use in your home (for cooking or body care), look for labels that say 'cold pressed' or 'expeller pressed' and 'unrefined' or 'virgin' for the most nutritional oils. The same goes for products with these oils in them.
Use Low or No Heat
Unrefined seed oils are more vulnerable to heat than their refined counterparts, so use them for low heat cooking or as a finishing oil in dressings & drizzles. Subjecting these oils to high heat breaks down their delicate health-promoting nutrients, and other less desirable compounds can be produced.
Check for Rancidity
All seed oils will eventually break down and become rancid as exposure to light, heat & air break down their fatty acid chains. Rancid oils no longer possess the flavor, aroma or benefits of fresh oils, and usually have a flat play-dough like scent.
Unrefined seed oils typically last between 6 months and 2 years, depending on the type, so check the shelf life of any oil you buy. Frequent use encourages longevity, so don't save it ~ enjoy it. If you're not using an oil often, you can store it in the fridge.
Always check the smell of an oil before you add it to your food or body care formulations. The aroma should have the same distinct aroma as the day you bought it. If it doesn't, compost the oil and get yourself a fresh bottle.
Our Stellar Ingredient: Sunflower Oil
The unrefined Sunflower oil we use to make Indigo Elixirs is sustainably grown, cold-pressed on Maui by Maiden Hawaii Naturals. And because Sunflower seed oil is one of the very few oils produced in Hawai'i (along with local Macadamia), it's the most sensible choice for us. Our culinary-grade Sunflower oil has a rich, nutty aroma, a deep golden hue, and a velvety feel on the skin.
Cold pressed, unrefined Sunflower oil is rich in linoleic acid, which strengthens the skin barrier & helps retain moisture, while vitamin E and other potent antioxidants protect against environmental stressors. As a gentle non-comedogenic & calming oil, Sunflower is helpful for sensitive or irritated skin. It also improves skin regeneration and promotes wound-healing, making it ideal for topical medicinals.
In Summary
Knowing how a given seed oil was produced, if it was refined, and in what way it's consumed is essential for understanding whether it contributes to health or dis-ease in the body. In general, you can assume that seed oils found in highly processed or fast foods are chemically extracted & refined, and these types of foods should be limited to rare & special occasions ~ not as part of your daily or weekly diet.
Cold or expeller pressed and unrefined oils, on the other hand, can absolutely provide nourishing benefits to a healthy diet & skincare routine. Just check the label and know what you are buying!