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Dietary Fats: The Good, The Bad, And The Ugly

Grass-fed Butter, healthy fats, CLA

By Dr. Mercola

Fats are an essential part of your diet. However, not all fats are created equal. So, how do you know you’re eating healthy, high-quality fat? In this interview, Dr. Cate Shanahan answers this important question.

Shanahan is a family physician and author of “Deep Nutrition: Why Your Genes Need Traditional Food,” originally published in 2008. A revised and updated version was issued this year. Herself an avid athlete, having competed in the Olympic Trials, she has also done consulting work for the Los Angeles Lakers.

Shanahan’s journey into nutrition started when she got sick. She ended up doing a deep dive into biochemistry and molecular biology, looking for a connection between her health problem and her diet, and found it didn’t reconcile with what she’d been taught in medical school.

“I was practicing family medicine in Hawaii at that time. I had gone to medical school with this fantasy that I would get to the underlying cause of diseases, particularly the ones that I tended to get as an athlete, which were connected to tissue.

I had bursitis and every ‘–itis’ … I was a runner … I actually had a scholarship [and] qualified for the Olympic trials [in] the 1,500-meter race …  In 2001 … I developed this problem in my knee where I ended up not being able to walk more than just a few steps without getting pain, swelling and fevers.

Going from being a high-level athlete, exercising an hour or two a day, to being couch-bound, I felt like my life was over … I didn’t know what was wrong. I’d had surgery. I’d gone to so many specialists and nothing helped.”

The Dietary Roots of Pain and Inflammation

Then, her husband suggested her sugar habit might have something to do with it. She would add a special concoction of caramel sauce and a quarter cup of sugar to her coffee every day. After running for 10 miles, she’d polish off a bag of M&M’s, thinking nothing of it since she wasn’t overweight and exercised.

“He physically handed me a book so that I could start reading it, because I was so stubborn,” she says. “The book he gave me was Andrew Weil’s ‘Spontaneous Healing: How to Discover and Embrace Your Body’s Natural Ability to Maintain and Heal Itself.’

The phrase that got me was [how] omega-3 fatty acids are like vitamins. That completely blew my mind because I thought fats were bad for you. They were all the same. I didn’t know there were essential fats the body needed for anything in particular that we couldn’t make …

I was like, ‘What? There are fats that are good for you? What is this?’ Even though I couldn’t walk, I flew to Oahu. I had to get a wheelchair through the airport so I could go to the medical library … This was 2001-ish. We didn’t have Google. Amazon didn’t deliver to Hawaii at that time …

I got three textbooks about fatty acids and biochemistry. I read them cover to cover. By the time I was done, I realized there was so much more to the science of nutrition than what we had learned.”

Surprise! Saturated Fats Are Good for You

As like so many other conventional doctors, Shanahan was convinced saturated fats were bad — very bad — and cholesterol should be avoided at all costs. Polyunsaturated fats like vegetable oils and margarine, on the other hand, were good for you. At that time, trans fats were largely unknown. Omega-3s also did not get much public recognition.

“I couldn’t believe it,” Shanahan says. “I was like, ‘How could all of medicine be so wrong?'” A key principle that made her realize the importance of dietary fats for health was the understanding of how fats oxidize.

Polyunsaturated fatty acids (found in vegetable oils) have highly perishable bonds that react with oxygen, creating a free radical cascade that turns normal fatty acids in your body into dangerous high-energy molecules that zip around, wreaking havoc in a way similar to that of radiation.

“I started listening more to my patients who were really into cooking … I realized that, really, the key thing as their connection to nature. They were in touch with everything … [They would] use every single part of the animal … they would eat everything … The fish, they would actually save the fish guts and start fermenting them under the counter for six months,” Shanahan says.

Considering the high amounts of sugar Shanahan used to eat, it’s quite obvious she was — like most people eating a modern, Americanized diet — burning sugar as her primary fuel. This caused mitochondrial dysfunction that, in her case, surfaced as inflammation in her knees. This is the premise of my new book, “Fat for Fuel: A Revolutionary Diet to Combat Cancer, Boost Brain Power, and Increase Your Energy.”

Like I did, Shanahan concluded that you actually need 60 to 85 percent of your daily calories in the form of fat. But not all fats qualify, and this is why Shanahan’s book is such a gold mine. She really gets into the details of the different kinds of fats, and explains why vegetable oils, such as soy, canola and corn oil, are so toxic to the human body.

This understanding is shared by only a tiny handful of lipid scientists in the world because it’s so technical, which is why we’ve not heard it brought into the forefront of nutrition science where it belongs, because it changes everything.

Vegetable Oils Decimate Health in More Ways Than One

The sad reality is that industrially processed vegetable oils are pervasive in the average American’s diet. Statistics show the average American gets somewhere between 30 and 50 percent of their calories from these oils — not because they cook with them, but because they’re in so many processed foods.

Refined processed vegetable oils are in salad dressings and in restaurant meals; they can even be labeled organic. The reason vegetable oils are bad for you have to do with their molecular structure.

“Vegetable oils are polyunsaturated. That means they have two double bonds [in close proximity]… That chemical structure has very important consequences for how these oils change when we manipulate them for processing and refining … and then again when they’re cooked with,” Shanahan says.

Polyunsaturated fat found in processed vegetable oils is not harmful in and of itself, but becomes so if and when you eat too much of it, and/or when the oils degrade, which occurs during refining, processing and heating (cooking). Not only can they form trans fats if heated high enough, but they can also form cyclic aldehydes, which are even more harmful.

If you regularly eat processed foods, you are virtually guaranteed to get too much of these oils — upward of 10 times more than your body can safely handle — and due to the intense refining and processing that goes into processed foods, the oils are going to be highly degraded and therefore toxic.

Oxidative Stress Is the Great Disease Maker

In Chapter 7 of “Deep Nutrition,” Shanahan details how polyunsaturated fats consumed in excess affect your liver proteins to cause arteriosclerosis, for example. This is why avoiding processed foods of all kinds is so important if you value your health.

“Oxidative stress is what happens when your body has all these free radicals deteriorating in your body. Oxidative stress is the great disease maker. Every chronic disease we now know is associated with oxidative stress. There’s not a disease you can name that isn’t … When there’s a lot of oxidative stress, your immune system doesn’t work as well.”

Ultimately, that oxidative stress impacts your mitochondria, which is why it produces so many symptoms. The mitochondria, of course, have cell membranes, and those membranes are made of fat, especially in your brain, and Shanahan does a great job explaining how damaged fats impact your brain health.

Omega-3s, CLA, healthy fats, dietary fats, whole food

Your Brain Needs Healthy Fats

Your brain is about 50 percent fat by dry weight, and about 30 percent of that are the essential fatty acids omega-3 and omega-6. Both are equally important, Shanahan notes. The problem is, most people get very little omega-3 and far too much omega-6, most of which is badly damaged by oxidation due to processing.

One of the reasons your brain is so susceptible to aging and age-related diseases is because you have high quantities of these highly reactive, easily oxidized fatty acids in your brain. To maintain optimal brain function, you need high-quality, undamaged omega-3s and omega-6 along with antioxidants to protect them from oxidation. In summary, processed vegetable oils are bad for your brain health for a number of reasons, including the following:

They are loaded with damaged omega-6 fatty acids without protective antioxidants

They strip your liver of glutathione, which produces antioxidant enzymes, which further lowers your antioxidant defenses

Most vegetable oils are made with genetically engineered (GE) crops designed to resist herbicides like glyphosate. As such, they’re typically far more contaminated with glyphosate than non-GE crops, and glyphosate has been shown to disrupt the tight junctions in your gut and increase penetration of foreign invaders, especially heated proteins, which can cause allergies

Toxic breakdown products found in vegetable oils inhibit an enzyme called delta-6 desaturase (delta-6). Perhaps the most important fat you need for brain and physical health is the omega-3 fat docosahexaenoic acid (DHA). DHA is absolutely critical because your body does not actually burn it for fuel; rather, the DHA gets integrated into your cellular membranes. DHA is also essential for the conversion of photons from the sun into electric current to energize your mitochondria.

Research shows that restricting omega-6 in the diet enables your liver to function better, allowing it to elongate short-chain omega-3s more efficiently. This process involves delta-6, and this enzyme is inhibited by toxic breakdown products in vegetables oils. High insulin levels will also inhibit this enzyme.

Cooking From Scratch Is Key

A key strategy for avoiding these pernicious toxins is to eat real food, and that means cooking most of your meals at home.

“The first step I recommend to my patients … is to start with a healthy breakfast … Have good quality pastured [grass fed, organic raw] milk or cream, if you can get it, or at least organic, in your coffee. That’s going to help you burn fat. No carbs, but plenty of healthy natural fat.

Grass-fed Butter, healthy fats, CLA, dietary fats, whole food

You could also have eggs with cheese, butter and maybe whatever vegetables you like for flavor — not the starchy vegetables obviously. Those are two examples of a really healthy breakfast … If you have a very high-fat breakfast … then you don’t have that hunger drive anywhere near as strong by lunch. You don’t have to snack … You can concentrate better …”

In the transition phase, when you’re initially teaching your body to burn fat as its primary fuel, you may be better off putting grass fed butter into your coffee instead, as milk has sugar in the form of galactose. Another important strategy is to avoid added oils and just eat the whole food that the oils are derived from. If you want avocado oil, use avocados. If you want flaxseed oil, use flax seeds. If you want sesame seed oil, use sesame seeds.

Olive oil is an exception as it’s not a processed oil. It’s actually pressed, although there’s the issue of adulteration. The vast majority of olive oil on the market is adulterated with other low-quality vegetables oils. Coconut oil is another exception from the above rule. As noted by Shanahan, “This is why when people go on the Esselstyn or the Ornish diet and avoid all added oils, they do experience benefits. [They’re] getting these toxic oils out of their diet.”

4-HNE — A Little-Known Toxin in Polyunsaturated Fats

Another important piece of information relates to 4-hydroxynonenal (4-HNE), which forms during the processing of most vegetable oils. 4-HNE is highly toxic, especially to your gut bacteria, and consumption of 4-HNE has been correlated with having an obesogenic balance of gut flora.

“They’ve actually done studies where they create fat mice and then take that gut flora from the fat mice and give it to skinny mice. It changes the way the mice behave. They get more anxious. Some of the mice will actually eat more. When I looked at this study, I said, ‘Well, how did they make these mice fat?’

What they were doing was feeding them a high-fat diet. Here’s where it gets really complicated … [M]ost of the studies on high-fat diets that use lard are using lard from animals fed corn and soy. [It’s] high in polyunsaturated fatty acids — nearly as [high] as if they were fed corn and soy oil.

So, these so-called high saturated fat diets are far from it. That means we have to rewind hundreds of millions of dollars’ worth of research into the so-called health harms of high saturated fat diets that were done in animal studies.”

4-HNE causes cytotoxicity and DNA damage, and instigates free radical cascades that damage the mitochondrial membrane. According to Shanahan, “You can’t design a better delivery vehicle for a toxin that’s going to destroy your health slowly over the course of maybe 10, 20 years, depending on the genetics of your antioxidant system capacity.”

Shanahan also notes that organic vegetable oil is not the answer here, as 4-HNE occurs even if the oil is obtained from organic crops. It’s an intrinsic byproduct of the refining and processing of the oil, no matter how healthy the oil initially was.

“As much as 5 percent of [a quart of vegetable oil] can be toxic types of trans fat. That is 50 grams. That’s almost 2 ounces. We’re talking about 2 ounces of a highly toxic compound versus parts per million, which you can’t even measure,” Shanahan notes.

Your Body Needs Real Foods

To learn more, I highly recommend picking up a copy of “Deep Nutrition: Why Your Genes Need Traditional Food.” As noted by Shanahan, “You’ve got to eat, so you might as well do it right.”

While the devil’s in the details, and the details may be complicated, the simplest way to understand what a healthy diet consists of is to think back 100 years or so and consider what food was back then, and how it was prepared. What you’re aiming for is real food — whole food that is as close to its natural state as possible.

This may be particularly important when it comes to fats. If you’re unsure, the easiest way to bypass potential hazards is to eat the whole food rather than the oil from the food, as some of the most dangerous toxins — such as 4-HNE — are a byproduct of processing.

“My husband likes to remind me that food should taste good, so you should enjoy what you’re eating. You will enjoy what you’re eating when you get these vegetable oils and too much sugar out of your diet. You will enjoy the healthy food a lot more. You’ll really appreciate it,” Shanahan says.

Coming Soon: ‘Fat for Fuel Ketogenic Cookbook’

I believe “Fat for Fuel” is one of the most important books I’ve ever written because it represents my worthy contribution to our understanding about preventing and healing disease. With all the information I packed into “Fat for Fuel,” it still didn’t provide the total picture. Although the book provides you with what changes are necessary and why to make them, you still need to know how to implement dietary changes and strategies.

That’s why I created a comprehensive companion tool, the “Fat for Fuel Ketogenic Cookbook: Recipes and Ketogenic Keys to Health from a World-Class Doctor and an Internationally Renowned Chef,” with celebrity chef Pete Evans.

Evans shares a dedication to eating healthy, fat-burning foods that are as scrumptious as they are nutritious. Together, we are delivering a full package of research-backed medical advice and kitchen-tested recipes that will empower you to make the shift to fat-burning and reap the powerful health benefits of the “Ketogenic Cookbook.”

The “Fat for Fuel Ketogenic Cookbook” will be released and available on November 14. If you wish to preorder your copy, CLICK HERE.


Dr. Joseph Mercola is a physician and New York Times best-selling author.

He was voted the 2009 Ultimate Wellness Game Changer by the Huffington Post and has been featured in several national media outlets including Time magazine, LA Times, CNN, Fox News, ABC News, the Today Show and The Dr. Oz Show.

His mission is to transform the traditional medical paradigm in the United States into one in which the root cause of disease is treated, rather than the symptoms.

In addition, he aims to expose corporate and government fraud and mass media hype that often sends people down an unhealthy path.