July 21, 2024

Layered with controversy and conspiracy, seed oils as a cooking ingredient are a hotly debated topic within the health and nutrition space, so the question remains: Are seed oils bad for you? Some warn that seed oils are toxic and extremely detrimental to our health. A quick search on TikTok will bring you straight to an endless feed of videos claiming that “seed oils are toxic.” Others reason that there’s no hard evidence to support these kinds of claims. Is there a clear-cut answer here? Before slipping down this oily slope and throwing away the contents of your pantry, here’s what the research and nutrition experts have to say about whether or not seed oils are as bad for you as you may have heard. 

What Are Seed Oils?

Seed oil is an umbrella term for a variety of vegetable-based, oftentimes refined oils. These include canola, soybean, corn, cottonseed, grapeseed, safflower, sunflower, rice bran, and peanut oils. All are typically created through synthetic chemical extraction methods that sometimes include additional processing like bleaching and deodorizing.

Do Seed Oils Offer Nutritional Benefits?

There are some nutritional benefits to seed oils, which vary depending on which type of seed oil you use. Here’s a look at what’s inside one tablespoon of canola oil, for example.

  • Energy – 124 kcal
  • Fat – 14 grams
  • Fatty acids – 1.03 grams
  • Vitamin E – 2.45 milligrams
  • Vitamin K – 9.98 µg

If you opt for grapeseed oil, instead, the composition will look a little different. Here’s a look at what’s inside one tablespoon of grape seed oil.

  • Energy – 120 kcal
  • Fat – 13.6 grams
  • Fatty acids – 1.31 grams
  • Vitamin E – 3.92 milligrams

Meanwhile, sunflower seed oil—a common cooking oil—looks different, as well. It contains more vitamins and some iron content, as well. Here is what is included in one tablespoon of sunflower seed oil.

  • Energy – 120 kcal
  • Fat – 13.6 grams
  • Fatty acids – 1.22 grams
  • Iron – 0.004 grams
  • Vitamin E – 5.59 milligrams
  • Vitamin K – 0.734 µg

Are Seed Oils Unhealthy?

Despite the fact that seed oils contain some vitamins and nutrients that are healthy for you, there are a few downsides to seed oils. Not only are the often used in many processed foods, but here are some of the biggest reasons why there’s so much hate for seed oils.

Low in Nutrients

When looking at seed oils from a nutrition perspective, the profiles across the different kinds are quite similar. Seed oils are a pretty high-calorie food without providing much in the way of nutrients, given that 1 tablespoon provides more calories than 3 ounces of smoked salmon, a cup of edamame, or 1/3-cup of ice cream. Whether it’s canola, safflower, generic “vegetable oil,” or another variety, 1 tablespoon of seed oil will provide approximately 120 calories, no protein or carbohydrate, and about 14 grams of fat. Also, some will have additional ingredients including soy lecithin, TBHQ (a preservative), and mystery additives that are extremely hard to pronounce, like dimethylpolysiloxane. 

High in Inflammatory Fats

One of the key aspects of the seed oil debate is their fat composition. Seed oils are a high-fat food—a label that we now generally understand isn’t always synonymous with “unhealthy”—but the kind of fat these oils contain is important to highlight. When looking at the different types of fatty acids, omega-3s tend to get a lot of positive press: They’re anti-inflammatory fats that can help reduce risk of chronic illness and improve heart health. Omega-3’s less-good-for-you counterpart, however, is omega-6 fatty acids, and most seed oils are predominantly composed of omega-6 polyunsaturated fats. These types of fat are widely considered to be inflammatory fats.

While it’s important to reduce chronic inflammation in our bodies, inflammation does serve us in notable ways, and we actually need some of both kinds of fats. (When we experience physical, chemical, or heat trauma, the inflammatory response that our bodies carry out helps prevent damage from spreading to nearby tissues, works to remove cellular waste and pathogens, and springs the healing process into action.) So we shouldn’t ditch all inflammatory fats.

Prone to Oxidation

Seed oils are more prone to oxidation due to their chemical structure. This means that they ultimately lead to the formation of free radicals, which are unstable molecules that can damage our cells and tissues. For example, the oxidation of seed oils can produce lipid peroxides. These are harmful compounds that degrade even further into other toxic substances like aldehydes and ketones. These substances have been linked to all sorts of health problems and chronic diseases like cardiovascular disease and cancer.

Linked to Obesity

One systematic review looking specifically at the omega-6 fatty acid linoleic acid, found that there was a positive correlation between linoleic acid concentration in fat tissue and diabetes, obesity, asthma, and coronary heart disease. Another review found that increased omega-6-to-omega-3 intake is correlated to increased risk of obesity.

Expeller-pressed seed oils tend to have higher levels of natural nutrients and antioxidants compared to oils that were extracted using chemical solvents and high heat. The lower temperatures involved in expeller pressing also reduce the risk of oxidation, which means that they’re less likely to contain those unwanted free radicals.

The Pros of Seed Oils for Cooking

Seed oils do offer some advantages in the kitchen, which is why so many people reach for seed oil when they throw on an apron. And WHarvard’s School of Public Health has published its stance on the topic, citing that science tells us there is no concrete evidence to support seed oils being toxic substances that should be avoided at all costs. With that in mind, here are some of the biggest benefits to cooking with seed oil.

Neutral Flavor

These highly processed oils offer a neutral flavor that will last for a long time in your pantry—and they’re extremely easy on the wallet. Unlike some other oils, like coconut oil, for example, you won’t really taste the seed oil in your food. Most of the time, it won’t tarnish or change the flavor at all.

High Smoke Point

They also have a high smoke point, the temperature at which an oil literally starts to smoke. Many seed oils’ higher threshold for heat makes them optimal for frying and high-heat cooking methods like roasting and sautéeing. If you’ve reached the smoke point while cooking, you’ll know it: Your eyes will be watering, your nostrils will be burning, and your dog will be quivering in the corner from the sound of smoke alarms.

When an oil begins to smoke, the enzymes, minerals, and other compounds in it start to break down and release free radicals. Free radicals are unstable atoms that can cause significant damage and inflammation to cells, leading to minor inconveniences like wrinkles all the way to life-changing diagnoses like cancer. What’s more, when oils are heated beyond their smoke point, a substance called acrolein is created, giving off the acrid taste and aroma of burnt food.

Lowers Cholesterol

Bianca Tamburello, RDN, a registered dietitian at FRESH Communications, says: “Critics caution that the omega-6 fatty acids found in seed oils can cause inflammation; however, there isn’t enough research to support the recommendation to stop eating seed oils. In comparison, there is a wide body of research that supports that polyunsaturated fats, like omega-6 fatty acids, support health by lowering cholesterol and contributing to better blood sugar control.”

One meta-analysis of four different randomized control trials, amounting to 660 participants, found there was insufficient evidence to determine that omega-6 fatty acid intake had a positive or negative effect on both cardiovascular disease outcomes and risk factors like elevated blood pressure or lab values. A review from 10 years earlier was also unable to determine any absolute correlation between increased omega-6-to-omega-3 intake and heart disease. A further meta-analysis looking at 30 studies encompassing results from over 1,377 participants found that increased dietary linoleic acid did not have any significant impact on blood levels of inflammatory markers. This review concluded the same results. And this study even found that omega-6 fatty acid intake was actually associated with lower levels of bodily inflammation.

Key Considerations for Consuming Seed Oils

With all this conflicting information, what food choices should you make when it comes to seed oils? The bottom line is that these oils aren’t necessarily the all-time healthiest option to cook with and consume in excess. But there’s no reason to panic and banish seed oils from your pantry and recipes altogether. That said, here are some helpful nutritional rules of thumb to abide by when it comes to using seed oils:

Moderation is the name of the game.

Using whole sources of seed oils in moderation—like whipping up a stir fry with a bit of canola oil or using some sunflower oil in baked goods—is definitely not going to endanger you, and may be a better-for-you alternative than something like bacon grease or shortening.

Opt for omega-3-rich oils when you can.

If you want to up your oil game and include more omega-3s into your meals, for olive oil or avocado oil. These are some of the healthiest oil options that have been linked to improved heart health, among other nutritional benefits. Plus, avocado oil has an added bonus of a high smoke point!

Limit processed food and packaged products that contain added seed oils.

“Seed oils are found in most processed foods such as chips, baked goods, and crackers,” Tamburello explains. “I recommend limiting these processed foods that are often high in added sugar, sodium, and fat—but [I don’t recommend cutting out] whole sources of seed oils.”

Frequently Asked Questions

  • What seed oils should I avoid?

    Seed oils do not have to be totally avoided. However, it is important to note that they are less nutrient-dense than other options. Try to avoid processed and packaged seeds that contain seed oils. This is an easy way to eliminate them from your diet partially.

  • is olive oil a seed oil?

    Olive oil is not considered to be a seed oil. It is considered a vegetable oil because it is made by pressing whole olives. And while some versions of olive oils may not remove seeds before pressing, it is still a higher ratio of olive to pit in the finished product. Seed oils are refined oils that come from only the seed portion of a plant.

  • How long does seed oil last?

    Seed oils can last up to nine months if stored properly. But, they can quickly become rancid if exposed to heat, air, and light. This can happen in as little as two months.

  • What are some seed oil alternatives?

    If you are trying to steer away from seed oil, you have other options for cooking and use in food. Olive, avocado, and coconut oil are great alternatives to seed oil, as is butter. All of these are lower in linoleic oil and are neutral-tasting.

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