why is seed oil bad for you

Why Are Seed Oils Bad for You?

This post may include affiliate links. See our affiliate policy for more details.

Last modified on December 20th, 2022

Why are seed oils bad for you, and what are they? These are questions you might be hearing a lot about lately. Many influencers are increasingly focusing on the negative effects of seed oils, and it seems there’s some validity to these claims.

Seed oils are obtained from some plants’ endosperm or seed instead of the pericarp fruit. Most vegetable oils are considered seed oils.

Many people aren’t even aware of what seed oils are or their negative effects. They’re hiding in very unsuspecting foods in many cases. Seed oils may be the leading cause of cancer, heart disease, and other chronic conditions, yet food makers continue to put them in primarily because they’re cheap.

Seed oils include:

  • Canola
  • Corn
  • Cottonseed
  • Sunflower
  • Safflower
  • Grapeseed
  • Ricebran
  • Soy

These are high in linoleic acid content. They, again, come from the seed’s oil, thus the name.

The History of Seed Oils

One thing to understand when answering why seed oils are bad for you is their history.

  • Seed oils were relatively recently introduced to our diets in the grand scheme.
  • Before the introduction of seed oils, common fat sources in the human diet were olive oil, butter and ghee, lard, suet from beef or mutton, and coconut oil.
  • Then, there was a shift. In 1961, the American Heart Association started recommending polyunsaturated fatty acids replace saturated fats.
  • There was the idea floating around that saturated fats were causing heart disease.
  • Medical organizations continue to reinforce this, pushing the consumption of vegetable oils like Crisco.
  • These changes led to replacing natural fats with the industrial seed oils that are so prevalent today.

Refined vegetable oils weren’t widely available until the 20th century when extraction technology became an option. Many seed and vegetable oils are extracted from plants using a chemical solvent. They’re then purified and refined. Sometimes, they’re chemically changed.

The steps to make industrial seed oils can include:

  • Gathering the seeds and then heating them to very high temperatures. The heating process causes the unsaturated fatty acids to oxidize.
  • The oxidization that comes from heat exposure creates byproducts that may be harmful to our health.
  • The seeds are processed using hexane or another petroleum-based solvent. This helps get the most amount of oil from them in extraction.
  • The industrial seed oils are then exposed to chemicals that deodorize them because they have a foul smell when they’re extracted. During deodorization, there’s the production of trans fats.
  • Then, the final part of the process is the addition of more chemicals to make the color more appealing.

These oils are frequently labeled as heart-healthy, but scientists are increasingly concerned about how much of these oils we consume.

Why Are Seed Oils Bad For You?

So, more specifically, why are seed oils bad for you? Below, we outline why more and more people are deciding to avoid seed oils in their diets.

Omega-6 Fatty Acids and Inflammation

Polyunsaturated fats are essential fatty acids. We can’t make them ourselves as humans, so we have to get them through diets.

There are two types—omega-6 fatty acids and omega xl. When we consume omega-6 fatty acids, they produce metabolites that can be inflammatory. These metabolites can include prostaglandin E2 and leukotriene B4. Omega-3 fatty acids include EPA and DHA, which are anti-inflammatory.

Our diets need a balance between omega-6 and omega-3 fatty acids. Typically, this balance should be 1-to-1. In western diets, we usually have ratios of omega-6 to omega-3 fatty acids that range from 10-to-1 to 20-to-1.

When you have high omega-6 fatty acids in your diet and a low intake of omega-3s, you’re more likely to experience imbalances in chronic inflammatory and mental health. The imbalance can contribute to chronic inflammation, which is part of many of the diseases we deal with today as modern humans, like cancer and heart disease.

We’re Not Evolutionarily Matched to Seed Oils

An evolutionary mismatch means our genes don’t align with our modern environments. This mismatch or lack of alignment is a primary driver of chronic diseases. Humans didn’t consume industrial seed oils until the 1900s. From 1970-2000, consumption of these oils went from four pounds per person a year to 26 pounds per person per year.

Linoleic acid, the main fatty acid in industrial seed oils, makes up around 8% of our total intake of calories. In hunter-gatherer ancestors, it made up only 1-3% of total calories.

They’re In Foods That Aren’t Good For You

Some bad things about seed oils aren’t the oils themselves but the foods they’re typically found in. These oils are neutral in flavor after processing and cheap, so they’re used in heavily processed and packaged foods. You’ll find them in chips and crackers, baked items, and margarine, and used for frying food in restaurants.

When you stop eating low-quality, processed foods, you’ll likely notice weight loss, more energy, and other health benefits.

Seed Oils Have Toxic Byproducts

When seed oils are manufactured, they’re made with heat and solvents. Hexane, as mentioned, is one material used to extract oil from seeds. This can then introduce molecules that aren’t stable and chemical additives. That can turn polyunsaturated fats into trans fats, which harm our health.

Hexane can be harmful to the environment even when inhaled, so consuming it regularly is likely especially detrimental to human health.

When seed oils are heated repeatedly to high temperatures, you get a buildup of potentially damaging chemicals. Factor deep fryers and restaurants are places where these fats keep getting reheated, making them potentially more harmful each time.

When repeatedly heated seed oils, depletes vitamin E, a natural antioxidant. It then leads to the formation of free radicals, which damage our DNA and cause oxidative stress. Repeatedly heated seed oils may be associated with liver and intestinal damage, heart disease, and high blood pressure.


The fatty acids in seed oils are very unstable, so as a result, synthetic antioxidants are often added to try and prevent them from going rancid and preventing oxidation. These synthetic antioxidants can come with their own set of problems.

For example, many are endocrine and immune-disrupting and also carcinogenic.

One synthetic antioxidant—TBHQ—may increase IgE response to food allergens. This can trigger a release of antibodies promoting food allergies.

What Health Conditions Are Linked to Seed Oils?

The consumption of seed oils may be linked to an increased risk of health conditions, including:

  • Asthma
  • Autoimmune disease
  • Depression
  • Anxiety
  • Alzheimer’s disease
  • Diabetes
  • Obesity
  • Heart disease
  • IBS and IBD
  • Inflammation
  • Infertility
  • Macular degeneration
  • Osteoarthritis

Many of the potentially devastating health effects of seed oils are because they can trigger chronic inflammation, thought to be a root cause of most chronic illnesses that accompany our modern lifestyles.

Can You Avoid Eating Seed Oils?

While you might understand now why eating seed oils is bad, they are hard to avoid.

  • You can first get rid of them in your kitchen, which is the somewhat easy part.
  • The next step is to avoid eating processed foods. If you’re serious about cutting out seed oils, you may have to avoid most restaurants because they are often cooked in repeatedly heated seed oils.
  • Eating grain-fed meat can be another part of avoiding seed oils. Grain-fed animals may accumulate the byproducts of seed oils, which can be toxic.
  • You should cook with extra virgin olive oil, coconut oil, and animal fats like butter and ghee.
  • Tallow and duck fat are also excellent animal fats for cooking.

Final Thoughts—Why Are Seed Oils Bad For You?

To sum up, why are seed oils bad for you? Seed oils are bad for you primarily because of how they’re processed and because they’re an evolutionary mismatch in our diets. Seed oils often have toxic byproducts, and they’re included in low-quality and processed foods.


Kresser, Chris. “How Industrial Seed Oils Are Making US Sick.” February 19, 2019. Accessed September 8, 2022.

Liao, Sharon. “Do Seed Oils Make You Sick?” Consumer Reports, May 31, 2022. Accessed September 8, 2022.

Ramsey, Drew, and Graham, Tyler. “How Vegetable Oils Replaced Animal Fats in the American Diet.” The Atlantic, April 26, 2012. Accessed September 8, 2022.

Mount Sinai. “Omega-6 fatty acids.” Accessed September 8, 2022.

Simopoulos, AP. “The importance of the ratio of omega-6/omega-3 essential fatty acids.” NIH National Library of Medicine, October 2022. Accessed September 8, 2022.

Pahwa, Roma, et al. “Chronic Inflammation.” NIH National Library of Medicine, June 19, 2022. Accessed September 8, 2022.

Pelc, Corrie. “Ultra-processed foods linked to heart disease, cancer and death, studies show.” Medical News Today, September 6, 2022. Accessed September 8, 2022.

Gunnars, Kris. “Are Vegetable and Seed Oils Bad For Your Health?” Healthline, December 12, 2019. Accessed September 8, 2022.

Leave a Comment

Your email address will not be published. Required fields are marked *

Subscribe For News and Updates on Health, Wellness, Vitamins and Supplements