Saturday, December 7, 2019

Retrospective #294: Saturated Fat, Heart Disease and the DGA

The Editorial Director of at Medscape Cardiology took on a challenging assignment a while ago. I decided to take on the assignment too, but steer my review using an alternate “selection bias” (mine). The Medscape review was designed to educate doctors. It gets a lot of the basics about saturated fats right and introduces the busy physician to newer concepts from “evidence-based” science. That’s a catch phrase that’s all the rage these days.
The setup: “Dietary guidelines for the prevention or treatment of coronary artery disease (CAD) have emphasized a reduction in the consumption of saturated fat since the 1960s.” A footnote in the review links to a 1961 piece in Circulation, the journal of the American Heart Association (AHA). January 1961 was when Ancel Keys, father of the diet/heart hypothesis, appeared on the cover of Time magazine and joined the board of the AHA. The setup continues: “Dietary saturated fat increases blood levels of low-density lipoprotein cholesterol (LDL-C) and subsequent risk of CAD, or so goes the conventional wisdom.” The “doubting Thomas” tone is appropriate, and was encouraging to me.
Tension rises: “The disparate findings have led to calls to stop demonizing saturated fat and equally vocal cries to proceed with caution before we let lard back into the menu.” The plot starts to thicken, introducing the “bad” guys.
Meanwhile, “the 2013 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines on lifestyle management to reduce CVD risk omitted a target for TOTAL dietary fat but did recommend a goal of 5%-6% of calories from saturated fat.” Three points: 1) The lead author of the ACA/AHA guidelines is Robert Eckel, professor of medicine at the University of Colorado. He is one of the protagonists in this story but is not introduced by name into the narrative until more than half way through; 2) Note the significant OMISSION of a target for TOTAL dietary fat. It was previously less than 30% of total calories; and 3) Note the limitation of SFAs to 5%-6%. It was previously 7%-10%.
The other protagonist in this set piece is Dariush Mozaffarian, dean of the Friedman School of Nutrition Science and Policy at Tufts University in Boston. He gets most of the science right (IMHO) – and I cannot emphasize that enough – but just cannot walk through the open door provided by the ACA/AHA’s omission of a target for total dietary fat. Instead, he is quoted as saying, “polyunsaturated fats are beneficial…” Perhaps this comment, taken out of context, reflects the author’s personal bias. By doing so, she becomes a third protagonist, representing the PUFA contingent.
Mozaffarian does disagree with Eckel’s 5%-6% limit on SFAs. “To derive a conclusion that saturated fat should be 5% of calories [as Eckel does] is not evidence-based,” he says. Other Mozaffarian quotes: “The School Lunch Program allows chocolate skim milk and banned whole milk. That’s absurd.” Another: “…the biggest driver of de-novo lipogenesis [where the liver makes fat from too many highly processed carbs] is the dose and speed that the carb is delivered.”
Mozaffarian begins a good discussion of LDL-C particle size, concentration, HDL-C and triglycerides with his comment that, “The U.S. view on saturated fat is totally based on the effects on LDL-C, and that’s why we have dietary guidelines to lower our saturated fat intake…”
My biggest gripe with the review was the author’s injection of an editorial POV about PUFAs. I think she pushes both Eckel and Mozaffarian, and Marion Nestle whom she quotes a few times, toward the Mediterranean “dietary pattern” touted by the 2010 Dietary Guidelines for Americans. It and the ACA/ADA guidelines were the cornerstone of the 2015 Dietary Guidelines for Americans, and are widely expected to remain so in the 2020 guidelines due out next year.
On a lighter note, my favorite parts of this Medscape piece were in the comment section. The best one, from Dr. J M, was: “Will the ghost of Ancel Keys ever be exorcised?” There’s also a very good one from Dr. Robert Hansen on “replacing SFA with PUFA [will] result in increased oxLDL and increased Lp(a) in humans.” In my opinion, Hansen is totally correct, but alas, his is still just a voice in the wilderness.
So, there’s evidence out there that there are a few doctors who are paying attention to the evolving cholesterol story, saturated fat and CAD, but many more, sadly, who are not. The story is, I think, both complex and complicated.

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