Perhaps you’ve noticed some “influencers” and others have been tossing around the term “seed oils” for a while now. Seed oils are nothing new; humans have consumed them for centuries. However, they weren’t always referred to as “seed oils”—that practice is only decades old. In the last few years, these oils have come under attack, labeled “toxic” and the cause of everything from heart disease and cancer to liver spots and brain fog. So do you need to worry about seed oils in your diet? In this post, I’ll break down the basics on these much-maligned oils. Then you can make informed decisions in the grocery aisles (and be able to separate truth from hyperbole).
What are seed oils?
Vegetable oils come from plant seeds, legumes, fruits, nuts, and grains. Manufacturers produce seed oils around the world, and some of the most commonly consumed include:
- Canola oil (rapeseed oil)
- Corn oil
- Soybean oil
- Sunflower oil
- Safflower oil
- Peanut oil
- Rice bran oil
- Grapeseed oil
Do seed oils contain healthy fats?
Nearly all the fats in our foods contain a mix of different types of fats. Seeds oils are predominantly polyunsaturated fats, a category of fats with two types: omega-3 fatty acids and omega-6 fatty acids. (Read more about the different types of fats in this post.) We need to get both of these types of fatty acids from food since our bodies cannot make them.
In general, we consider polyunsaturated fats (and monounsaturated fats) more heart-healthy than saturated fats. But there are some differences between how omega-3s and omega-6s operate in the body. Omega-3 fatty acids tend to be slightly better at fighting chronic inflammation in the body than omega-6s. And seed oils are higher in omega-6 fatty acids and lower in omega-3s. This ratio is one of the talking points of the “anti” seed oil folks, often presented as being “bad.” However, being less good doesn’t automatically make it bad (very few things in nutrition are black and white).
This case is a good example of that. And specifically in this case, a significant body of research shows that consistent consumption of the most common omega-6 fatty acid, linoleic acid, does not increase inflammation markers in the body. (In some cases, it actually lowers them.) Eating a heart-healthy diet doesn’t mean eliminating omega-6 fatty acids. In fact, a diet containing omega-6 fatty acids correlates with improved cardiovascular health and improved glucose metabolism.
How are seed oils produced?
Making seed oils starts with whole seeds (such as chia, sunflower, or sesame). From there, the production process is basically the same as for some other commercial vegetable oils. The seeds are first pressed to force out the oil, then a chemical process extracts the remaining oil. Hexane, a solvent, combines with the pressed plant material and then heats. Next, the hexane evaporates and is captured, and any remaining oil in the pressed seed mixture releases. Distillation removes the last traces of hexane, and then the oil is bleached and deodorized. (Bleaching removes components that may cause the oil to spoil faster.)
There is evidence that inhaling hexane (the most common way to expose people) can be dangerous. But at this point, there is no evidence that possible trace amounts in seed oils are harmful. You can also find seed oils from smaller companies that are only pressed and not chemically treated. But expect those to be more expensive and spoil faster.
How does Guiding Stars evaluate seed oils?
Guiding Stars has an algorithm specifically for fats and oils and foods made from them, like salad dressings and mayonnaise. Our algorithms evaluate foods—including fats and oils—based on their nutrient characteristics, not their source. Within the fats and oils category, products earn credits for the presence of omega-3 fatty acids and monounsaturated fatty acids. And they receive debits for saturated and trans fats. Look for Guiding Stars icons on shelf tags at participating stores to find nutritious options.
The Guiding Stars Scientific Advisory Panel constantly monitors the health research and scientific consensus about foods and food ingredients. Then we update our algorithms to reflect established science.
Will avoiding seed oils improve my health?
Health status varies widely from person to person, and is dependent on many variables. A dietary change that benefits you may have no impact on someone else. Are you concerned about seed oils or any other food or ingredient in your diet? If so, consult your physician or a Registered Dietitian for the personal attention you deserve.
Most seed oils are consumed in refined, packaged snacks and fried restaurant food. So you can automatically cut back on them by eating fewer of these types of foods. And there are other dietary changes you can make to lower chronic inflammation in your body (and thereby decrease your risk of chronic diseases) if that’s your goal:
- Eat more whole foods like fruits, vegetables, lean proteins, whole grains, legumes, nuts, and seeds. And eat fewer packaged snacks such as crackers and chips.
- Cook at home more often than eating out. First, use Guiding Stars to select nutritious ingredients. Then prepare your own meals to have greater overall control over your food.
- Use monounsaturated and polyunsaturated fats instead of saturated fats whenever possible. Saturated fats like coconut oil, butter, and lard are widely known to be more inflammatory.
- Cut back on deep-fried foods and fast food. Unhealthy compounds can build up when seed oils reach very high temperatures (and are then reused), like in restaurant fryers. At home, we don’t heat seed oils to temperatures high enough to cause this problem.
- Add more omega-3 fats to your diet by eating more seafood. Fish and shellfish are good sources, but heart-healthy omega-3s show up in other foods too.