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Diet Study Outcome? Work It; Flip It; Reverse It!

Conclusions about diet study outcomes that are this precarious, that can be worked just a bit, and flipped -- are utterly useless. They are propaganda.
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I confess here, as I have done to my kids, that I have never fully understood what Missy Elliott was talking about in her song, Work It. I get the general impression it's better off that way.

That notwithstanding, and renouncing any links to salacious innuendo, I am obligated to offer the performer a shout-out of thanks for her lyrics: work it; flip it; reverse it. They pertain beautifully to diet study outcomes, and what those serving their established self-interests and prefabricated conclusions are prone to tell you they mean.

I have two illustrations for you, and then a general conclusion.

The first, and more recent of the two is the study that allegedly told us vegetable oil is bad for us now. I have cited the study, and addressed it in some detail before, so I'll keep this at a rather high level. In brief, the article examined data from 50 years ago, and found no obvious, short-term benefit of very high-dose corn oil over saturated fat among the very small percentage of trial participants who stuck with the program for a year.

Again, it's not my intent here to get into the particulars of methodologic merits, or demerits. I've already done so, and others have as well, more thoroughly than I. Let's just stick with the outcome.

On the one hand, the study -- at least superficially -- does say that high-dose corn oil is not "better" than saturated fat. The camp currently advocating for more meat, butter, cheese; and telling us that saturated fat is "good" for us now has, predictably, embraced that message, and Praised their Lard, accordingly.

But just a moment, now. Work it; flip it; reverse it.

If there was no discernible heart disease difference between those chugging corn oil, and those consuming more saturated fat -- it says, just as plainly, that saturated fat is not "better" than high-dose corn oil. The very same "eat more saturated fat" camp tends to make a lot of noise about the harms of vegetable oil. Some simply argue that vegetable oils, not animal fats, have been our real problem all along. Others dive deeper to talk about omega-6 fats, and their pro-inflammatory effects.

But those details don't matter. It gets very simple, very quickly, once you work it a bit. If this study is invoked because of what it shows about dietary fat and heart disease, then you have to make a choice. If saturated fat is "good" for us, so is high-dose corn oil -- because the outcomes were the same. If high dose corn oil is "bad" for us, then so is saturated fat -- because the outcomes were the same. The conclusion being promulgated, in other words, is not about the data, or epidemiology -- it's just about ideology. If you work it just a bit, it's unavoidable that you flip it, and reverse it. If this study is an argument "for" saturated fat, it's an argument for high-dose corn oil. If it's an argument "against" high-dose corn oil, it's an argument against saturated fat.

Frankly, I don't think it's either -- both because of the nature of the study, and because these polarized, either/or, my-way-or-the-highway proclamations about nutrition tend to be self-serving nonsense. Excessive saturated fat from the usual dietary sources remains harmful. So, too, is an extreme imbalance in unsaturated fats, whether the product of chugging corn oil, or simply eating the typical, and lamentable, American diet. Moving on.

The second illustration is an older vintage, although the message of it remains timely. When a meta-analysis came out in 2014 finding that heart disease rates were effectively the same for those in the top, and those in the bottom tertile of saturated fat intake, members of the church of latter day saturated fat canonizers were again quick to pounce. We were told, in various prominent fora, that here was proof we had been wrong all along about saturated fat, and -- the real problem was sugar.

But, again, let's work it. This 2014 meta-analysis was the successor to a prior, 2010 meta-analysis that had shown much the same. Intriguingly, and maybe even inscrutably, the 2014 meta-analysis did not address what was replacing saturated fat calories, even though this was the final line of the abstract of the earlier paper on the same topic: More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat.

How a paper on the very same subject four years later managed to ignore this clear mandate altogether, I don't quite understand, and have chosen to file under: "whatever."

In any event, I was pretty sure I knew, back in 2014, what had replaced saturated fat calories when they went down. We know that Americans aren't eating more broccoli. Our misguided forays into "cutting fat" translated, through a combination of demand-side naïveté and predatory profiteering on the supply side, into Snackwells, donuts, and multi-colored marshmallows masquerading as "cereal." If that conjecture on my part was right -- that lower saturated fat intake meant higher sugar intake, and vice versa -- then this study was suggesting that each was exactly as bad as the other.

My impression resided in the realm of speculation only very temporarily. Researchers at Harvard took on the mantle of the "instead of what?" question with which the 2010 meta-analysis concluded. Their findings, published in 2015 in the Journal of the American College of Cardiology affirmed my intuition on the topic, but more importantly, the predictable conclusions to anyone with a valid, working knowledge of nutrition. When saturated fat calories were replaced by trans fat calories, things went from bad to worse. When replaced by sugar and refined starch, they remained comparably bad. When replaced by either unsaturated oils from their customary sources (e.g., nuts, seeds, olives, avocado, fish), or by whole grain calories- heart disease rates declined markedly.

So, that 2014 meta-analysis did, indeed, suggest that saturated fat was not appreciably worse for us than what was replacing it -- namely, sugar and refined starch. But it showed with exactly comparable clarity that saturated fat was no better for us, either, since heart disease rates were the same at both ends of the scale. You don't have to work the "saturated fat is not the problem since it's no worse than the alternative" conclusion very hard to flip it, and reverse it: it's no better, either. However bad sugar we know excess sugar to be for us, the recent studies most routinely invoked to make that argument say just the same about saturated fat.

Conclusions about diet study outcomes that are this precarious, that can be worked just a bit, and flipped -- are utterly useless. They are propaganda. They serve procrastination, and often profits, but not public health, and not progress.

What we know reliably about diet and health is not born of such noisy nonsense. It is not the product of hyperbolic headlines, or polarizing ideologies. It derives from the weight of evidence, from epidemiology, from enduring effects in actual populations, and from a global consensus of temperate judgment conjoined to actual expertise. It tells us that a sequence of scapegoats has done nothing for health, while providing cover for a variable feast of highly profitable junk food.

Studies suggest that an excess of saturated fats mostly from animal sources are about as bad for us as a massive imbalance in unsaturated fats from plant sources. Studies suggest that health suffers commensurately from an excess of saturated fat, or an excess of sugar. Science and sense alike suggest that the way to fix this is not to choose one nutrient nemesis over another, but to eat a diet of wholesome foods, mostly plants, in a sensible and time-honored assembly, and get all the nutrients right.

The take-away? Trust no conclusion that when so lightly worked, reverses so readily, and flips so fully.


Director, Yale University Prevention Research Center; Griffin Hospital

Senior Medical Advisor,