Saturday, March 7, 2015

The Nutrition Debate #294: “Saturated Fat and CAD: It’s Complicated”

Tricia Ward, Editorial Director of at Medscape Cardiology, took on a challenging assignment with this long survey piece. I’m taking on the assignment too, but I will shorten and steer my review using my “selection bias.” The Medscape review is a good piece, generally, designed to educate doctors. It gets a lot of the basics about SFAs right and introduces the busy physician to many aspects of newer concepts from evidence-based-science. That’s a catch phrase that’s all the rage these days. It was deployed here, I think, to draw a stark contrast with the now widely disparaged diet/heart hypothesis.
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.” Here a footnote links to a 1961 piece in Circulation, the journal of the American Heart Association (AHA). Note: 1961 was the year that 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 an encouraging start.
The 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.” Now, 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%. That’s a significant reduction. (This is about 11g or 2.25 teaspoons of butter for a person eating 2000 calories a day.)
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, Ward quotes him as saying, “polyunsaturated fats are beneficial…” Perhaps this comment is taken out of context by Ward and reflects her personal bias. And 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 [from the DASH study, as Eckel does] is not evidence based,” he says. Other Mozaffarian gems include: “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 body fat from large slugs of liquid or other highly processed carbs] is the dose and speed that the carb is delivered.” Ward explains, “In terms of foods, a bagel or soda consumed in isolation is more likely to trigger [the liver making fat] than a small amount of potato mixed with vegetables and oil.”
Mozaffarian’s 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…” begins a good discussion of LDL-C particle size, concentration, HDL-C and triglycerides.” The article gets into the weeds a bit but it's good and, as I said, it is written for a technically savvy reader.
My biggest gripe, and personal bias, besides giving Eckel and the ACA/AHA guidelines so much play, was Ward’s transparent injection of her own 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 are widely expected to be repeated in the 2015 Guidelines due out in less than a year. Why, you ask?
Alice H. Lichtenstein, D. Sc., is Vice-chair of the 2015 Dietary Guidelines Advisory Committee and is in charge of drafting the document. Lichtenstein was also the lead author on the AHA’s current “Diet and Lifestyle Recommendations.” And she also served on the AHA committee in which Robert H. Eckel, M.D. was co-chair and lead author of the above mentioned “2013 AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk. Together, they are a formidable force today.
On a lighter note, my favorite part of this Medscape piece is the comment section. You can link to it here.
The best one, from Dr. J M, was: “Will the ghost of Ancel Keys ever be exorcised?” There’s also a very good one by Dr. Robert Hansen on “replacing SFA with PUFA [will] result(s) in increased oxLDL and increased Lp(a) in humans.” BRAVO! Take a look, if you feel up to it. In my opinion, Hansen got it right, 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 story of (dietary cholesterol), saturated fat and CAD, and many, sadly, who are not. The story, I think, is perhaps more complex than complicated.

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