The Definitive Guide to Saturated Fat
by Mark Sisson
Mark's Daily Apple
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Almost anyone can agree with the basic tenets — eating more vegetables, choosing only clean, organic meats, and getting plenty of sleep and exercise is fairly acceptable to the mainstream notion of good nutrition. The concept of Grok and a lifestyle based on evolutionary biology can be a harder sell, but anyone who's familiar with (and accepts) the basics of human evolution tends to agree (whether they follow through and adopt the lifestyle is another question), at least intellectually. But saturated fat? People have this weird conditioned response to the very phrase.
“But what about all that saturated fat? Aren't you worried about clogging up your arteries?”
In fact, “saturated fat” isn't just that; it's often “artery-clogging saturated fat.” Hell, a Google search for that exact phrase in quotations produces 4,490 entries (soon to be 4,491, I suppose). Most doctors toe the company line and roundly condemn it, while the media generally follows suit. The public, unsurprisingly, laps it up from birth. The result is a deeply ingrained systemic assumption that saturated fat is evil, bad, dangerous, and sinful, a preconceived notion that precludes any meaningful dialogue from taking place. Everyone “knows” that saturated fat clogs your arteries — that's treated as a given — and attempting to even question that assumption gets you lumped in the crazy category. After all, if you start from such a “fundamentally incorrect position,” how can the rest of your argument be trusted? Thus, talk of the superior cardiovascular health of the Tokelau (with their 50% dietary saturated fat intake) or the Masai (with their diet of meat, blood, and milk) or the Inuit (with their ancestral diet of high-blubber animals) is all disregarded or ignored. If they even deign to listen to the facts, they'll acknowledge the existence of healthy populations eating tons of saturated fat while muttering something about “genetic adaptation” or “statistical outliers.” It's all hogwash, and it's infuriating, especially when there's so much literature refuting the saturated fat hypothesis. If you're interested in more information on these three oft-cited high-saturated fat groups, check out Stephan's entries on the Tokelau, the Masai, and the Inuit.
It all started, of course, with the infamous Ancel Keys and his Seven Countries Study, which tracked the fat consumption and heart disease levels of various nations. It was named for the seven countries that saw an increase in heart disease cases correspond with increased fat consumption, but it should have been named the Twenty Two Countries Study for all the data he omitted. Data, I should mention, that demolished his hypothesis of fat intake causing heart disease. The original paper noting Keys' omissions was largely ignored and is tough to track down, but Peter over at Hyperlipid had access to it and shows the original graph with all the nation data included (with the Masai, Inuit, and Tokelau thrown in for fun represented by the red dots).
Try drawing a straight line through those data points… I dare you! As you can see, there is a faint, weak correlation between fat intake and heart disease, but it's just that: a correlation. It shouldn't confirm anything except the need to run controlled experiments to directly measure the effects of dietary fat. Unfortunately, that correlation was enough to get Keys the front cover of Time and widespread acclaim as the father of dietary science. His hypothesis gained traction in the scientific community and mainstream CW, a position it has never really relinquished. Subsequent controlled experiments to measure the effects of saturated fat have been either inconclusive, poorly designed, or completely unsupportive of the saturated fat-is-evil hypothesis, but because the starting point assumes it to be true, those inconclusive or unsupportive results become aberrations while the poorly designed studies become canon. Meanwhile, Keys' peer, British scientist John Yudkin, was finding even more compelling connections between dietary sugar and heart disease, but his ideas gained no traction and garnered no significant follow up experimental studies. Keys got the cover of Time and heaps of public adulation; Yudkin was relegated to publishing now-out-of-print books, writing letters to scientific journals (PDF) that were only ignored, and languishing in relative obscurity. Americans, as you can guess, got the real shaft. I suspect I'm getting a little off track here, so I'll just point people toward Good Calories, Bad Calories for a full discussion of the Yudkin-Keys issue.
For a quick summary of the Ancel Keys debacle to send to friends and family worried about your saturated fat intake (who might not be interested in reading a blog post), check out this quick clip from Fat Head.
What is Saturated Fat, Exactly?
Saturated fatty acids (SFAs) are referred to as saturated because all available carbon bonds are tied up with a hydrogen atom. That is, there are no openings for rancidity or spoilage, whereas a polyunsaturated fatty acid containing two or more pairs of double bonds without hydrogen atoms occupying the open space is wide open for oxidation. SFAs are shelf-stable, resistant to heat damage, and essential to many bodily functions. Roughly half of our cell membrane structure is composed of saturated fat, and saturated animal fats, like butter or fatty organ meats, contain huge amounts of essential fat-soluble vitamins (K2, A, D, among others). (Sure, you could just take them in capsule or liquid form, but the very fact that these (universally praised) vitamins naturally occur in evil saturated fat indicates that maybe, just maybe it's not so evil after all. Researchers were particularly dumbfounded at one study (PDF) indicating high-saturated-fat fermented cheeses containing large amounts of Vitamin K2 actually reduced cardiovascular mortality, but they soon came to their senses and recommended opting for supplements rather than real food. Ridiculous.)
Saturated fat is also a fantastic source of energy, at least if you trust your body to make the right decision — otherwise, why else would we store excess carbohydrates as saturated body fat? In fact, when we burn body fat for energy, either through exercise or through dieting, we are quite literally consuming huge amounts of saturated (and monounsaturated) fat. Body fat is energy to be used for later; dietary fat is energy to be used immediately. Whether you're burning through your stores of adipose tissue or downing flagons of warm ghee, all that fat goes through the same processes in your body to be converted to energy. Burn your ass flab, take a bite of fatty rib-eye — it doesn't matter. Your body treats that fat the same way. As Richard and Tom have said before, losing weight is like eating pure lard, which has nearly the same fatty acid composition as human adipose tissue. To vilify saturated fat is to assume that, over the span of our evolution, our bodies have somehow developed a predilection for a deleterious energy source that contributes to cardiovascular disease. That's absolutely preposterous, unless Darwin and company somehow got it all wrong with the whole natural selection thing. Somehow, I'm leaning toward trusting the millions of years old case study known as evolution.
Where Do They Get Off, Anyway?
Since Keys has been thoroughly discredited (not if you ask most people with any real say in the matter) and there are plenty of examples of groups eating a high saturated fat diet and retaining optimum cardiovascular health (“Those are just outliers!”), how does the outcry against saturated fat continue unabated? Well, it all starts with cholesterol, yet another vilified substance that our bodies naturally produce because, well, it's completely essential to proper bodily function (though if you listen to the experts, our bodies are suicidal entities who can't be trusted to do the right thing). Elevated cholesterol has long been fingered as a player in cardiovascular disease, and saturated fat has been shown to increase cholesterol levels, so saturated fat is therefore to be avoided. Sounds relatively sound. So high total cholesterol levels are bad, right? Not so fast.
As I detailed in my last big post on cholesterol, total cholesterol doesn't tell the entire story, and it doesn't even necessarily indicate risk for cardiovascular disease. Just take a look at the graph plotting global total cholesterol versus cardiovascular disease. There's absolutely no positive correlation, and there may even be a negative correlation. Far more likely is that there's no connection at all.
September 30, 2010
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