Fats That Heal, Fats That Kill — 40 Yrs Later

In 1986 I bought a book that changed how I taught nutrition at Shape-Up. It was called Fats That Heal, Fats That Kill, by a Canadian researcher named Udo Erasmus. I still have my original copy. At the time, the entire country was deep in the low-fat craze. Fat was the enemy. Grocery shelves filled with “fat-free” cookies, “lite” dressings, and margarine that we were told was heart-healthy.

I stood up in front of my members and said something that sounded almost reckless then: the right fats are not the problem — they are essential, and the war on fat is going to make us sicker.

I was president of a small American Heart Association chapter representing Newport Beach in those years, and later helped create the larger Newport/Mesa/Irvine chapter for Orange County, where I served as Chairman of the Board. I once gave a talk on fats with cardiologists in the room shaking their heads at me. Good, respectful disagreement — but disagreement all the same.

Four decades later, the science has largely caught up to what Udo and a handful of others were saying. Not all of it — Udo got some things wrong, and I’ll be honest about those too. But the core idea has held up better than the low-fat dogma ever did. And in the last few years a new oversimplification has taken its place: the “all seed oils are poison” panic now flooding social media. Both extremes miss the real story. So let me give you the honest update — what’s true, what’s overstated, and exactly how to buy good oil.

The mistake we made: blaming the wrong thing

For fifty years we’ve argued about the wrong question. We’ve fought over which fatty acid is the villain — saturated fat, then cholesterol, now omega-6 “seed oils.” But the most important truth about oils is not really about the molecule at all. It’s about what happens to that molecule before it reaches your fork.

Here’s the part that finally makes everything fit together, and it’s exactly what Udo was pointing at in 1986: fats and oils are the most fragile nutrients we eat. They are damaged by heat, light, oxygen, and time. A fat that is genuinely healthy in its fresh, whole-food form can become genuinely harmful once it has been industrially refined, deodorized, hydrogenated, or repeatedly heated in a fryer. Same fatty acid. Opposite effect. The difference is the damage.

This single idea resolves a paradox that confuses almost everyone in the seed-oil debate. Linoleic acid — the omega-6 fat that “anti-seed-oil” voices warn about — is a good example. When researchers measure it in people’s blood (a far more reliable method than asking what they ate), higher linoleic acid generally tracks with lower death rates, lower heart disease, and no rise in inflammation markers. Large pooled studies of hundreds of thousands of people point that way. Yet the same fatty acid, when overheated in a deep fryer, breaks down into toxic compounds that are unquestionably bad for you.

So who’s right — the seed-oil defenders or the seed-oil critics? In a sense, both, because they’re talking about two different things: the fresh fat versus the damaged fat. Udo had the framework for this before most of the labs did.

What the science actually supports today

Let me be careful here, because your trust depends on me not overselling.

Trans fats were the real catastrophe — and on this, the establishment was right. The partially hydrogenated oils that replaced butter and lard during the low-fat era turned out to be the most clearly harmful fats ever added to the food supply. Udo was warning about them in 1986; the FDA didn’t finish banning artificial trans fats until 2018. That’s three decades of damage we could have prevented. When I disagreed with my fellow Heart Association colleagues, this was the heart of it — we were so afraid of natural fats that we embraced a manufactured one that was far worse.

The blanket “all saturated fat is deadly” message was an oversimplification. The relationship between saturated fat and heart disease is real but more modest and more individual than the 1980s version claimed. What you replace it with matters enormously — swap saturated fat for refined flour and sugar and you gain nothing; the low-fat, high-sugar decade helped fuel the obesity and diabetes epidemic we’re still living in.

The “seed oils cause heart attacks and cancer” claim is not supported by the weight of evidence. I know this isn’t the popular position in wellness circles right now, but I won’t tell you something the data doesn’t back. The strongest “seed oils are toxic” arguments lean on a couple of reanalyzed trials from the 1960s and 70s that used extreme amounts of safflower and corn oil (and, in one case, also contained trans fats). The much larger body of modern evidence does not show that fresh dietary linoleic acid, in normal amounts, causes these diseases.

*What is solidly supported is this: oxidized, damaged, and repeatedly heated oils are harmful, and we are eating far more of them than any prior generation — mostly because we eat out and eat processed food far more than we used to. That’s* the lever worth pulling.

The biggest hidden problem: the restaurant fryer

If I could change one thing about how Americans eat, it wouldn’t be the bottle of oil in your pantry — most of you can manage that. It would be the oil you can’t see: the fryer oil in restaurants.

Here’s what happens. The longer an oil sits in a hot commercial fryer, the more it degrades into what chemists call “total polar compounds.” Once those exceed about 25 percent, the oil is considered degraded, and eating food cooked in it has been linked to higher blood pressure, arterial damage, and other harms. Much of Europe legally caps frying oil at that threshold and inspects for it. The United States, for the most part, does not test or regulate this at the restaurant level. An American fryer can legally run oil long past the point another country would force a change.

And the toxic breakdown products don’t stay in the fryer — they migrate into the food. University of Minnesota researchers showed that a toxic aldehyde formed from overheated oil ended up inside fried potatoes at roughly the same concentration found in the oil itself. When investigators have sampled real restaurant fryers, a large share of the oil was heavily oxidized. You are quite literally eating the damage.

This is why the type of oil restaurants use compounds the problem. The seed oils that make up the great majority of restaurant frying oil are high in fragile polyunsaturated fat, which degrades fastest under sustained heat. It’s a double hit: a fragile oil, reused for hours or days.

I want to be fair: eating fried food once is not a health emergency, and it’s the repeated, sustained reuse — not the seeds themselves as some sermon would have it — that does the harm. But if you eat out several times a week, deep-fried food is worth treating as an occasional indulgence, not a staple. When you eat out often, lean toward grilled, roasted, steamed, or sautéed dishes, and save the fryer for now and then.

Is anyone regulating this?

It’s a fair question: if degraded frying oil is harmful, does anyone make sure restaurants change it? In much of the world, yes. Most European countries, along with India, Japan, and China, set a legal limit on frying-oil degradation — usually around 25% total polar compounds — and inspect for it, forcing kitchens to discard oil once it crosses the line.

The United States has no such national standard. An American fryer can legally run oil far past the point those countries would require a change, and nothing on the menu tells you how old the oil is. One honest caveat: even the polar-compound test isn’t perfect — in at least one restaurant survey it understated how oxidized the oil truly was — so regulation helps but doesn’t fully solve the problem. The practical takeaway is the same either way: in this country, the freshness of the oil your fried food was cooked in is essentially unregulated and invisible to you, so when eating out, the safe assumption is that the oil has been in that fryer a long time.

You may not even have the good oil you think you have

Here’s something that genuinely surprised me when I dug into it, and it will surprise your friends too. The premium oils we trust most — extra virgin olive oil and avocado oil — are among the most counterfeited foods in America.

University of California, Davis tested avocado oils and found the great majority were either rancid before their expiration date or diluted with cheaper oils — and a few bottles labeled “pure” were essentially soybean oil. A follow-up found the same pattern in store-brand oils. The reason is almost absurd: until late 2024, there was no legal definition of what “avocado oil” even had to be. The international food-standards body (Codex Alimentarius, run by the UN’s FAO and WHO) finally adopted a purity standard in November 2024, which is real progress, but enforcement on store shelves is still catching up.

Olive oil has its own long history of fraud and quality problems — much of it is not outright fake, but a great deal sold as “extra virgin” is rancid or has degraded to a lower grade by the time you pour it.

The lesson isn’t to give up on these excellent oils. It’s that the label alone can’t be trusted — you have to buy on verification. Which brings me to the practical part.

This is a much longer article I wrote for my upcoming book Shape Up For Life I intend to release later this year. Below is a link to the whole article if you are interested more in this topic I am passionate about.