Friday, August 26, 2016
Pseudoconfusion about saturated fat: 5 reasons for 1 hot mess
I know, you keep hearing conflicting reports about saturated fat and health outcomes. So do I.
A colleague circulated this study, purportedly showing no association between saturated fat intake and heart disease in a cohort of Dutch adults. Except, the study also reported, rather as an afterthought, that half of all the saturated fat in question was palmitic acid, a saturated fatty acid found in palm oil, dairy and meat; and that variation in palmitic acid did predict variation in heart disease rates. Honestly, I had trouble making sense of this 1, and that's my job.
It's also hard to reconcile the gist of this new paper with a recent, rather mammoth study out of Harvard, showing rather decisively that higher intake of saturated fat leads to increased risk of early death, while increased intake of polyunsaturated and/or monounsaturated fat reduces mortality.
Since all of this has something to do with what we all choose to eat every day, and since diet is long, even anciently, established as the veritable cornerstone of health, then “hard to reconcile” and “trouble making sense” are not a good place to get stuck! We really do need to know the truth, and frankly, I think we do.
We are not actually confused, neither about the basic care and feeding of Homo sapiens in general, nor about the role of saturated fat from the usual sources (i.e., meat, dairy, certain cooking oils, and the parade of processed products incorporating and adulterating these) in our health. What is being propagated is pseudoconfusion, and I have identified 5 common reasons for it.
1) Inattention to: instead of what?
Most of the academic discourse, and attendant pop-culture chatter over recent years about the potentially unfair indictment of saturated fat for crimes against humanity traces its origins to two widely cited meta-analyses, one published in 2010, the other in 2014. They share a very important blind spot. Both looked at variation in saturated fat intake and variation in cardiovascular disease and mortality, finding no meaningful association. Oddly, though, the first of these papers, four years before the second, noted its blind spot: it had not asked or examined the “instead of what?” question. In other words, the study was completely inattentive to the foods being eaten more often when pepperoni pizza was being eaten less often, or vice versa. It noted that future studies on this topic should certainly ask and answer the critical “instead of what?” question, particularly in a society so prone to move from 1 kind of junk food to another. For reasons I've never entirely understood, the 2014 paper did not do so, again looking at variation in dietary fat and health outcomes, but not at change in overall diet pattern or diet quality.
Fortunately, a still more recent study did just that, asking when people eat less saturated fat, or more, what do they eat more (or less) of instead, and how does that affect health outcomes? The answer this time was concordant with both the weight of evidence, and just plain sense. When saturated fat calories were replaced by trans fat calories, things went from bad to worse (i.e., heart disease and mortality rates went up). When they were replaced by sugar and refined starch, as has happened so often when people “cut fat” by eating Snackwells, rates of chronic disease and premature death remained comparably high both times. But when saturated fat calories from meat and dairy were displaced by either whole grain calories, or unsaturated fat calories from nuts, seeds, olive oil, avocado, and fish, rates of cardiovascular disease and mortality went down significantly.
The bottom line: we cannot understand the implications of more or less X as a percent of our total calories, without attention to the Y that replaces it.
2) Disregard for the role of ranges
Major studies cited to show that saturated fat is “fine” now because its variation does not lead to variation in heart disease suffer from another rather flagrant limitation. They are often conducted within a given country or culture, be it the U.S. or the Netherlands or wherever else, and the range of variation in saturated fat intake is quite narrow. If you are comparing, for instance, the top and bottom quintiles of saturated fat intake here in the U.S., and the vast majority of us consume some version of the typical American diet (and we do, which is why it is “typical”!) ― then the extremes of that range are not very far apart. Yes, you can find exceptionally high and extraordinarily low intake levels here, but those disappear into rounding errors when conducting a population-level study.
How does this matter? Well, consider a study to determine if parachutes can save the lives of people who fall out of planes. Now, imagine 1 study compares parachutes that are 1 square inch in total surface area to parachutes that are 1.25 square inches in area. Would you expect to see any difference in survival rates? Of course not. But now imagine the headlines: “parachutes useless; size does not matter …”
Conversely, in a comparison of parachutes of 350 square feet (a realistic surface area) vs. 348 squqre feet, other things being equal, would you expect to see a survival difference? Again, almost certainly not. Now the headline is: “parachutes work every time, no matter how small …”
The bottom line: if variation in X is being examined to explain variation in Y, then it matters whether or not X varies much in the first place.
3) Dietary tunnel vision
Let's imagine we hear that saturated fat from, say, butter, may help protect us against type 2 diabetes, at least a bit. But, unfortunately, we also hear it appears to increase the risk of both heart disease and mortality a bit as well. In fact, we recently heard exactly that.
Yes, but, the headlines tell us: butter fat protects against type 2 diabetes! And that story goes round and round. Relative to Coca Cola and donuts, it's probably true. What's missing?
Any mention of all the foods long known to protect against diabetes and against heart disease and premature mortality overall! What foods do that? All the good sources of soluble fiber, like beans, lentils, whole grains, berries, apples, and so on. All the good sources of monounsaturated fat, like nuts, seeds, olives, and avocado.
The problem here is talking about one food or nutrient at a time, as if the rest of the diet, the rest of the food supply, and other options didn't exist. If you are at high risk for type 2 diabetes and hear enough times that dairy fat may help protect you, at the cost of other risks, you may feel as if you have no choice, and have to take your chances. Looking at diet and health outside the tunnel of that one study, however, shows choices very clearly. There are dietary patterns, foods, and food combinations repeatedly, and decisively linked not just to less diabetes risk, but better health overall. There is a pretty big difference between “this may help you in some ways and is just as likely to hurt you in others” and “this is almost certain to help you in every way.” But with any given study and any given news cycle, that critical part of understanding routinely fails to make the cut.
The bottom line: the best ways to the best outcomes routinely reside with foods and diets outside the tunnel vision of a study with a single nutrient focus.
4) Conflating lack of harm with good
This item is the cousin of #3 above. Let's say the evidence showing harms from saturated fat really is much less damning than we thought at the height of the “just cut fat” craze. It is.
The next obvious question, and one routinely neglected, is: does relative lack of overt harm define a “good” food? It hardly pays to dignify so silly a question with an answer, but let's: hell no! Food is our fuel, construction material and sustenance. It is supposed to be good for us! Lack of harm, let alone relative lack of harm, is an absurdly low place to set the bar.
So, what is the evidence that dietary patterns high in saturated fat from the prevailing sources, baked goods, processed dairy products, processed meats, and so on, produce the health outcome that matters most, longevity combined with vitality, anywhere in the world? There is none. The longest-lived, healthiest populations vary widely in their total fat intake, but they all consume diets of mostly wholesome plant foods, which tend to be low in saturated fat. In North Karelia, Finland, heart disease rates were reduced 82% and life expectancy increased by 10 years with a shift from higher intake of animal foods and saturated fat to a higher intake of plant foods and a significant reduction in saturated fat.
The bottom line: good food should be held to a much higher standard than “maybe not quite as harmful as we once thought…”
5) Neglecting the link between planet and plate
Finally, and emphatically, the day has come and gone when any of us can think about diet for health without factoring in the fate of the planet. There are no healthy people without a viable planet to live on, and prevailing dietary patterns are an even more obvious threat to the world around us than to the biological world within each of us.
My friend and colleague, S. Boyd Eaton, is one of the founding fathers of our modern understanding of the Paleo diet. Anyone who claims to know anything about that diet is effectively obligated to cite the scholarly contributions of Dr. Eaton and his associates. I defer to him on this topic.
Prof. Eaton states emphatically that we need to eat less meat, for 2 reasons, one minor, the other major. The minor reason is that most of the meat most modern people eat is nothing at all like the pure meat of wild game that was the only option in the Paleolithic. There was, as I have noted before, no Paleolithic pastrami, or bacon, for that matter.
The second, major reason, and again, this is Prof. Eaton talking, not me, is that we were isolated, scattered bands in a vast, empty world of seemingly limitless resources during the Stone Age. We are a global, marauding, devouring horde of over 8 billion now. We cannot be hunter-gatherers, and we cannot be substantially carnivorous without annihilating the very biodiversity that sustains us. Dr. Eaton thinks we can learn something from our Stone Age intake of protein, but need to translate it into plant sources, no matter how much we might like meat.
The bottom line: Dorothy, we aren't in the Stone Age anymore!
If the status quo were harmless, I could look on passively as pseudoconfusion propagates it. But the status quo is anything but. Each new lap we take to nowhere leads to a few fewer intact ecosystems; a few fewer intact fisheries; a few fewer species enriching the biodiversity of this planet; a few fewer glaciers; a few more inches of sea level; a few more days over 90 degrees; a few more droughts, and few more floods. What is threatened, ultimately, is that our home will simply become inhospitable to our kind. We are all just part of the same, single, planetary game of survival, and will win or lose collectively.
In other words, every lap to nowhere makes the mess down here a bit messier. And yes, of course; hotter, too. The risk is that we relinquish control of the menu entirely until there is just 1 featured dish: our cooked goose.
David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.
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