Vegetables are healthy. But vegetable oil is deadly. Say, what? How can vegetable oil be bad for you? For many people, this is one of the most confusing things about nutrition. In this post, Jenna Witt, a Nurse Practitioner (NP) functional medicine practitioner and certified health coach—and let’s not forget super mom of 4—explains why vegetable oils are horrible for health. Especially these 5 worst vegetable oils. 

I grew up with Crisco coursing through my veins. My momma would fry or bake anything with this all-American vegetable shortening. (Shortening: a fat that turns solid at room temp.) God, did she make the best pie crusts ever! I’m drooling just thinking about it. But I do my best to just say no to my mom’s pies. That’s because even though they are mouthwatering, they contain a deadly substance…

No, I’m not talking about sugar. Not this time at least. The deadly stuff in my mom’s glorious pie crust is the Crisco itself, i.e. vegetable oil.  

Why Is Vegetable Oil Bad? 

It sounds confusing, right? How can vegetable oil be bad for you when vegetables are so good for you. That’s the ultimate nutrition paradox.

Yes, whole vegetables are superfoods. This is especially true of low-starch veggies like dark leafy greens and cruciferous ones like broccoli and cauliflower. 

But vegetable oils are terrible for health for a few different reasons. Food manufacturers use vegetable oils (seed oils are also bad) because they are cheap and they extend shelf life. When food manufacturers add hydrogen to vegetable oil, the hydrogenated oil makes food last forever. That’s why Twinkies never spoil. 

So what’s so bad about eating something that extends shelf life? After all, if vegetable oil helps a product last longer, maybe it can help us live longer? 

Well, unfortunately, that’s not the case. Just imagine if it were true. The PIE DIET. I’d be the first to sign up for that. LOL. 

Many studies (like this one) show that vegetable oils create free radical damage. Free radical damage is when your DNA can’t be repaired. If your DNA is under constant assault, premature aging happens. And it’s not just wrinkles you have to worry about. DNA damage results in disease. 

In addition, eating lots of food with vegetable oil causes chronic inflammation in the body. Could it be that your joint pain is because of Crisco? 

Omega 3’s vs Omega 6’s

You’ve probably heard of omega 3’s and 6’s. But if you’re not sure what they are and how they affect your health, I’ll break it down in a simple way for you. 

Both are essential fatty acids. Fatty acids are components of dietary fat just like amino acids are the building block of protein. They are essential because your body doesn’t create them on its own; you need to get them from food. 

A diet that’s rich in omega 3’s is associated with healthier outcomes for cardiovascular health and cognitive function. But a diet that’s high in omega-6’s is associated with disease. But if omega 6’s are essential, why is that the case? 

The answer is that when it comes to omega 6’s you need to consume the just-right Goldilocks amount. For much of humankind, people ate roughly the same amount of 3’s and 6’s. But these days, because of Crisco and some other bad vegetable oils I’ll warn you about below, people are eating 15 or even 20 times the amount of omega 6’s to omega 3’s. 

That’s a recipe for obesity, type 2 diabetes, heart disease and chronic joint pain. Mom: I love your dang pie but I’ll indulge just once or twice a year. 

The 5 Worst Vegetable Oils To Consume 

The lesson is that yes, omega 6’s are necessary for our health. But we’re getting them from the wrong sources. And public enemy #1 is vegetable oil. When vegetable oil is exposed to heat in cooking or from direct sunlight, the oil easily spoils. So there’s the double whammy of high omega-6s and rancidity. 

Eating rancid oil can lead to plaque deposits in the arteries (atherosclerosis). 

If you want to avoid chronic inflammation in your body, avoid these 5 worst vegetable oils. Truth be told, there are several vegetable oils that easily could make this list. But because they are the most common, they make my list:

  • Corn oil (83 times more omega 6’s than omega 3’s!) 
  • Soy oil (only 8x more but most of it is genetically modified)
  • Safflower oil (133x more 6’s)
  • Canola oil (good ratio but most of it is genetically modified)
  • Cottonseed oil (the original Crisco; 54x more 6’s)

Runner’s up for worst vegetable oils

  • Grapeseed oil (a whopping 676:1 omega 6 to 3 ratio!)
  • Peanut oil (32:1; tastes great in Thai food but keep to a minimum)
  • Palm kernel oil (mostly saturated fat)

Best Oils For Health

The best oils might be more expensive than Crisco. But isn’t your health worth it? In my diet coaching programs, I recommend to my health coaching clients avocado oil, walnut oil and olive oil (but don’t cook at a high temperature). 

Even a dab of grass-fed butter or good-old fashioned organic lard is better to coat your frying pan with than vegetable oil. Yes, too much saturated fat can be harmful for your health. But saturated fat doesn’t spoil like vegetable oil. That’s why I say just a dab will do. 


I know it may sound confusing but trust me. Vegetable oils are terrible for your health. The good news is you can have your pie and eat it too. Just replace that Crisco with a healthier oil or fat. If you need some hand-holding with your health goals, book a complimentary discovery session with me now. 

Until next time, 

Jenna Witt, NP