If you looked no further than this first sentence, could you name the 5 worst cooking oils for your health?

Just guessing, but I would bet that even if you could name them, you still regularly consume at least one of them. And if you eat in restaurants often, you most assuredly consume some of them.

If you research the topic of cooking oils, you will find varying opinions and “facts”. And if you read labels on the food you purchase, you will also find them among the ingredients in many, many foods.

But the oils I list in this post were the ones most named by nutritionists as being bad for your health. I also spoke with a Certified Nutrition & Wellness Consultant to verify that these cooking oils are not healthy ones.

In no particular order, these are the 5 worst cooking oils listed by reputable sources:

  • Sunflower seed oil
  • Canola oil
  • Palm oil
  • Corn oil
  • Soybean oil

You may be surprised to see canola oil and corn oil, probably because in the past they have been purported to be healthy oils for cooking. And you might think that “vegetable” oils would be healthy. But don’t let that terminology fool you.

Let’s back up and talk about what you should consider when choosing a cooking oil. There are 4 main factors that affect the healthiness of a cooking oil. (If you want more information on any of the following factors, just click on the underlined term.)

The first is smoke point. That means when an oil with a low smoke point is heated to high temperatures, it becomes oxidized and damaged, causing it to generate free radicals. Free radicals in your body can cause inflammation, raise cholesterol levels, and contribute to the development of cancer.

Therefore, for cooking at high temperatures, you need an oil with a high smoke point because it remains stable at high temperatures.

The next factor to consider is fatty acid ratio.  The most important fatty acid ratio to consider is omega 6 (polyunsaturated) fatty acids to omega 3 (monounsaturated) fatty acids. You may have noticed labels that tout omega 3 fatty acids in them, such as eggs.

Omega 6 fatty acids are very common in foods, and while that is not a bad thing, it is easy to overeat a high ratio of omega 6 fatty acids to omega 3 fatty acids, which can cause inflammation in the body

What you should be aiming for is a more balanced ratio of omega 6 to omega 3 fatty acids, which may mean you need more omega 3 fatty acids added to your diet.

The third factor to consider when choosing a cooking oil is GMOs. Corn and soybean oils are very likely to be GMO (genetically modified organisms), as 94% of cooking oils from these two sources in the U.S. are genetically modified. Genetically engineering these crops makes them more resistant to herbicides and pesticides that are sprayed on crops to prevent weeds and bugs from attacking them.

Although we still don’t know the long-term effects of GMOs, there is enough evidence to support avoiding them altogether.

The final factor that should affect our choice of cooking oil is how they are produced and processed. Many oils are extracted by using high heat and/or chemicals. This means they may become oxidized (see smoke point information above) before being bottled.

Therefore, the safest oils should be unrefined to preserve their nutritional benefits.

So, if the aforementioned oils are bad for your health, what should you do?

Check out my next post on “The 5 Best Cooking Oils for Your Health”!


Don't miss any of the posts, emails, and freebies of this March – June exploration of the world of food, which covers meal planning, meal prep, and making healthy food choices. Click on the Subscribe button on this page so you won't miss any of the action.


I’m Vicki Peel, former home economics teacher and educational administrator. If you are not receiving my emails, coupons, and freebies, look for the Subscribe block (below right) and submit your contact information. I will not share your information with anyone, and all the content you will receive as part of our community is free. I may occasionally promote someone else’s paid content, offer a product for your consideration or share an item that I think might be of use to you. However, you are under no obligation to purchase anything – ever. So, sign up now so you won’t miss anything during our March – June foods extravaganza!!