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Are Rancid Oils Irritating Your Gut

author avatar Dr. Eric Berg 02/15/2020

Let’s face it - most of us love to eat fatty foods.

If you’ve been following me for even just a short while, you know I strongly recommend the high-fat Healthy KetoTM diet. With its focus on healthy fats such as nuts and olive oils, there is abundant evidence that your health will benefit when you include these fats in your diet.

Yet there’s a potential downside even to healthy fats, not to mention the unhealthy ones that abound in our culture, tempting us with their flavor that’s designed to hook us on them.

In this article, I’ll cover:

Let’s dive in.


Why Fats Turn Rancid

When oil or fat goes rancid, it’s called rancidification. Rancidification is caused by either incomplete or complete oxidation; meaning, the fat molecules have degraded. When this happens, your health can be affected.

Normally, healthy fats come with their own antioxidants like Vitamin C and Vitamin E to protect them from oxidizing. But when they’re exposed to light, oxygen, or heat, or processed, the antioxidant protection can break down, especially in the unsaturated fats that are present throughout most of our food supply. These fats are:

  • Soy
  • Corn
  • Canola
  • Cottonseed

They’re all highly susceptible to oxidation, especially if they’ve been opened and exposed to oxygen. (Saturated fats such as butter don’t normally turn rancid.)

When oil becomes rancid, it gives off a certain smell or taste that people have described as:

  • Musty
  • Sour
  • Bitter
  • Metallic

It’s noticeable - you can’t miss the odor or objectionable taste.

And it’s not just an unpleasant smell or disgusting taste you have to deal with.


How Rancid Oils Can Damage Your Body

Rancid fats are actually toxic to your cells and even your genes, if you consume them in large amounts. You may think you’re safe, but even small amounts can irritate certain parts of your body, especially the first part of your small intestine and bile ducts. What’s worse, rancid oils can cause inflammation and irritation, making your gallbladder feel like it’s swollen.

It can also cause damage due to free radicals, which are unstable molecules that can damage the cells in your body. Free radicals form when atoms or molecules gain or lose electrons. If you eat an unhealthy diet, or you smoke, or are exposed to environmental sources of free radicals like radiation, drugs, and pesticides, your risk of damage to your cells and organs increases. Aging leaves you more susceptible too.

Even though you believe you’re consuming a small amount of rancid oils, there’s a distinct possibility you’re eating far more than you realize.


Why You May Be Consuming More Rancid Fats Than You Realize

What’s particularly troublesome is that many people are consuming large amounts of rancid oils without even knowing it.

Here’s why.

The oils I listed above are in over 60 percent of foods in a typical grocery store. Thus, you’re likely getting nearly constant exposure to them through your habitual food shopping choices.

Not to mention that restaurants reuse oil over and over again when preparing deep-fried foods. I’m not talking only about fast food places! So if you eat out and feel sick or bloated, particularly under your right rib cage, rancid oil could be the cause.

a photo of pieces of fried chicken

Fortunately, there are some simple steps you can take to drastically reduce your consumption of oils that may be rancid.


What You Can Do To Sharply Decrease Your Consumption Of Rancid Oils

I recommend you stay away from soy, corn, and canola oils. Most if not all of them are genetically modified, which is another factor that contributes to these oils’ toxicity in your body.

Carefully read labels of processed food. When one of these oils is high up in the list of ingredients, don’t buy it or eat it.

When you eat out at a restaurant, avoid deep-fried foods. If your preferred dish says it’s sauteed, ask your server if your dish can be cooked in butter.

See? Easy!


How To Reduce The Chances Of Healthy Fats Turning Rancid

Although I’ve focused so far on unhealthy fats, the truth is that even healthy fats like olive oil and nuts can turn rancid.

If you’re like most people, you probably have a stash of nuts such as almonds, walnuts, or pecans that have been sitting in your cupboard a little too long.

Here’s what I recommend to limit your exposure to rancid nuts with their risk of creating an inflammatory response in your body:

  • Find a company that sells fresh nuts, rather than ones that may have been sitting on the grocery store shelf for months
  • If you can check the nuts for freshness before you buy them, do so. For example, you may be able to check the nuts sold in bulk containers.
  • Keep nuts in the refrigerator. If you bought a lot of them, take out the amount you want to eat. Soak them in water overnight. In the morning you can dry them out. This will start the germination process, which gets rid of what are called the enzyme inhibitors and makes the nuts easier to digest. Just make sure you eat the amount you soaked within a short period of time, so they don’t have a chance to go rancid.

a handful of fresh nuts

Regarding olive oil - I’m quite picky! I prefer fresh olive oil. It has a very distinct flavor and aroma that you can learn, in order to easily distinguish between fresh and rancid. Although some people have described the odor of rancid olive oil as being similar to mouse urine, it should be easy to tell if it’s gone bad!

a dark bottle of olive oil


Your Health Can Benefit When You Stop Consuming Rancid Fats

Most of us cringe at the idea we may be eating rancid fats.

After all, even the word “rancid” can make you feel nauseated, never mind the notion that you may be unwittingly consuming them.

Now that you’ve discovered the damage that rancid oils can cause, and how simple it is to avoid them, I’m confident you have the information you need to take charge of this crucial area of your health.

You can reduce or even eliminate the ways that rancid fats sneak into your diet. All it takes is a little commitment on your part to follow the suggestions I’ve made here. Then you can feel reassured that you’ve taken a valuable step towards supporting your health.

Time to get started!

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Disclaimer: Our educational content is not meant or intended for medical advice or treatment.

Editor’s Note: This post has been updated for quality and relevancy.


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