Truth about Saturated Fat
Truth about Saturated Fat
We have known for a long time- many years- that all saturated fat is not created equal with regard to health effects. The details of a discussion encompassing, for instance, just stearic acid, lauric acid, palmitic acid, and myristic acid- to say nothing of caprylic, caproic, butyric, enanthic, and so on- could take many interesting pages. Suffice to say: some saturated fatty acids are quite convincingly established to be harmful, and others are not.
Here, “convincingly established” refers not to one favored study, not the latest spate of hyperbolic headlines, and not someone’s effort to sell the newest book of dietary revelation- but the weight of evidence. We know what we know most reliably when mechanistic studies in cell culture and animal models align with biomarker studies in people, and when those in turn align with outcome studies and intervention trials in people, and when those in turn align with observational epidemiology at the level of whole populations. Our knowledge of saturated fat is informed by just such evidence, spanning species, decades, methods, and populations.
Regarding mechanisms of effect, there is one especially salient refrain among those championing saturated fat for health: it tends to raise HDL levels. Yes, that is true. But does that actually validate the agenda of the “eat more meat, butter, and cheese” crowd? No, for two reasons.
First, the obvious one. You can have low HDL but feel fine and never get heart disease; or have enviably high HDL, but have a massive MI. Which would you prefer?
The point is that none of us really cares about our blood levels of HDL, or any other moiety for that matter, other than as proxies for health outcomes that actually affect our lives. High HDL is desirable only if and when it signifies a lower risk of cardiovascular disease. That’s what actually matters.
But doesn’t a higher HDL reliably guarantee lower heart disease risk? Absolutely not, and for a reason that is all but intuitive with a simple analogy.
Consider, for instance, an argument that good urine output is an indicator of healthy kidneys, vitally important for control of blood volume and consequently, blood pressure (an established fact). Now, consider that a high intake of, let’s say, pickles, increases urination. The obvious argument by the International Confederation of Pickle Pushers is: See! Good urine output is good for blood pressure, and pickles increase urine output- so pickles are good for blood pressure!
But don’t sign up for the pickle-juice diet just yet. You see what’s going on, right? The rather massive sodium load from pickles is actually prone to raise blood pressure, and blood volume, and the urine output is simply the body attempting to keep up, and compensate.
I don’t know for sure if that applies to the effects of saturated fat on HDL, but I find no clear indications in the scientific literature that it does not. In other words, maybe a rise in HDL from saturated fat intake is a genuinely good thing, but we can’t reliably reach that conclusion. Maybe HDL goes up because confronted with more saturated fat, the body NEEDS more HDL. Maybe “saturated fat raises HDL” actually translates to: saturated fat stresses the body, and the body does what it can to compensate.
Mechanistic studies suggest less inflammation and atherogenesis when saturated fat intake is reduced, and replaced by unsaturated fats. Intervention studies show similar benefits when a baseline diet with many liabilities, a high load of saturated fat among them, is replaced with either a Mediterranean diet high in unsaturated fats, or a diet low in total fats. Dramatic declines in cardiovascular disease at the population level over a span of decades have been observed in North Karelia, Finland, where a reduction in saturated fat intake was among the priority interventions.
Also in the real world, the longest-lived, most vital populations on the planet vary widely in their intake of total fat, but none has a high intake of saturated fat. The idea that a diet high in saturated fat “could” be as good is a leap of faith. The call to “jump” is more often than not issued by those with something to sell you.
The truth about saturated fat is not unsettled. What is unsettled is: can we handle the truth?
Saturated fat need not be exonerated, let alone canonized, to make the case that excess sugar is bad for us, too. Our appetite for sound bites and hyperbolic promises, and our antipathy for the more measured character of reliable truth, does nothing to advance our health. It simply encourages us to keep exploring new ways of eating badly. Until we decide to change it, that, sadly, is the truth.