What Are Seed Oils? And How Do You Know If You’re Eating Them?

“Seed oil” and “vegetable oil” sound like innocent, maybe even vaguely healthy, terms. In actuality, they refer to a process of hydrogenation rather than just the oils naturally occurring in seeds and vegetables. They’re in just about all the processed food we eat, and are likely a major culprit in the obesity epidemic we're facing today.

By Alina Clough3 min read
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By now, most people have seen the term “seed oil” floating around. While the usage ranges from a well-memed punchline to a more serious call to action around public health, it’s generally not well understood. Some even speculate that seed oils, also called vegetable oils, are the hidden culprit behind the rampant rise in Western obesity rates over the past few decades, though the advice from experts is muddled with conflicts of interest.

Still, aren’t we just talking about vegetables and seeds? What could possibly be unhealthy about that? Well, not exactly. “Seed oils” and “vegetable oils” refer to oils that have gone through a hydrogenation process, a type of processing that many speculate is what gives them their nasty side effects. These days, seed oils are pretty hard to avoid. Outside of fruits, vegetables, and meat, they’re in pretty much everything in the grocery store thanks to their versatility and subsidized price point. So what exactly are seed oils? And how do you know if you’re eating them?

(Don’t) Trust the Process

Let’s first debunk the most common misconception: Seed oils aren’t just ground up seeds. Unlike, say, olives, which naturally produce oils, “seed oils” refer to the process needed to produce them, not what they’re made of. Specifically, when nutritionists refer to “seed oils” or “vegetable oils,” they’re talking about the highly-processed product of a process called hydrogenation. Hydrogenation was invented in the late 1800s to make oils into solids, and involves neutralizing and bleaching the oil, then using a catalyst such as nickel to create a reaction between the oil and hydrogen – thus the term “hydrogenation.” 

“Seed oils” refer to the process needed to produce them, not what they’re made of.

Processing the oil this way is extremely helpful for food chemists, providing them with a more versatile product than would naturally come from seeds and vegetables. They’re much more shelf stable, extending the life of products far more than more natural fats like butter, and they allow for further processing since they can be heated to much hotter temperatures than butter for things like frying foods. They’re also way cheaper, thanks in part to the fact that many agricultural lobbies have succeeded in getting the government to subsidize many of the ingredients seed oils are made from: canola, soy, and sunflower. McDonald’s was one of the first corporations to take notice of this at scale, switching their fries from being fried in beef tallow to a canola-blend in 1990. All of this means that if you head to the grocery store, you’ll be hard pressed to find virtually any packaged foods without hydrogenated oils in them. That is, unless you’re savvy.

What’s in a Name?

“Hydrogenated oils” don’t exactly sound appetizing, and manufacturers realize that. Especially in recent years, health conscious consumers have begun reading ingredient lists more often, sometimes relying on heuristics like “not eating things you can’t pronounce.” Unfortunately, many seed and vegetable oils have innocent sounding names that are very easy to pronounce. Terms like sunflower oil not only pass the “easy to pronounce” test, but they even sound vaguely plant-based and healthy. The following terms are a short list to keep in mind if you’re trying to avoid hydrogenated oils in your next trip to the grocery store:

  • Canola (rapeseed) oil

  • Soybean oil

  • Sunflower seed oil

  • Rice bran oil

  • Peanut oil

  • Safflower oil

  • Hydrogenated oils

  • Vegetable oils

  • Grapeseed oil

Big Fat Nutrition Issues

Our consumption of oils has skyrocketed in recent years, mostly due to changing dietary recommendations. In the ‘80s and ‘90s, concerns over saturated fats led nutritionists to begin recommending a switch from solid fats like butter to liquid ones like seed and vegetable oils. Per capita consumption has ballooned in recent decades, from around 4 pounds per person per year in the ‘70s to 26 pounds per person per year in 2000, and these rates don’t look like they’ll be slowing down any time soon. The idea was that switching from solids to liquids would help reduce saturated fat intake, initially thought to be the main culprit of our health woes. Oils do reduce our intake of saturated fats, but they’re rich with unsaturated fatty acids. One in particular is speculated to be the reason for negative health effects: linoleic acid.

Linoleic acid appears to cause obesity and diabetes at much higher rates than either saturated fats or fructose. 

While they’ve only involved mice so far, experiments have shown that increasing linoleic acid consumption in the quantities that American diets have, from 1% to 8% of total calories, stimulates greater food consumption, increases the size of fat cells, and masks fullness cues in the brain. It also appears to cause obesity and diabetes at much higher rates than either saturated fats or fructose. Human studies, though less robust at this point, have shown similar trends. For instance, substituting with saturated fats (the kind we consume in animal products) promoted a reduction in abdominal fat, whereas substituting with linoleic acid made participants’ cholesterol worse and may have made them even fatter.

Closing Thoughts

While it’s pretty tough to avoid all seed oils (outside of a pretty strict whole food diet), cutting back is likely to benefit your health in a number of ways. Processed food isn’t doing our bodies any favors, and hydrogenated oils are one of the worse culprits. If you’re looking to detox from seed oils or just cut back, familiarizing yourself with all of their different aliases is key. While government regulators and the companies who fund them may not always be the strongest advocates for your health, taking control of what you’re eating is luckily something you can do all by yourself.

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