Monday, March 21, 2011

Symposium on reducing dietary saturated fat

     The latest issue of the American Journal of Clinical Nutrition has a perspective article highlighting topics discussed at an international nutritional symposium (Nutrition Symposium).  The goal of the symposium was to reach an expert consensus on the current state of research regarding the evidence for the reduction of dietary saturated fat for the prevention of cardiovascular disease (CVD).  There were several notable researchers.  This included Walter Willett, the nutrition research juggernaut who leads the ongoing Nurse's Health Study, and Ronald Krauss, whose research describes the deleterious effects of high carbohydrate diets on LDL particle and subsequent atherogenicity.
     The article seemed oddly cold and ambiguous.  While this may seem like an odd criticism of a scientific article, I usually characterize scientific writing as calculated and skeptical.  Perhaps it was just strange to see how little confidence the experts had on the available data which have been used to establish a very specific and rigorous public health message; that is, "reduce your saturated fat intake.  I don't care how you do it. Good God! Why aren't you reducing your saturated fat intake?!"
    Regardless, there were some interesting and important topics discussed:

1.  Given that some evidence, but certainly not all (my words), indicates that it is beneficial to reduce saturated fat intake, there is insufficient research examining what nutrients should replace it.  Thus, replacing saturated fat with transfats or carbohydrates, especially refined carbohydrates, likely offers no benefit and may increase the risk of CVD.

2.  There is actually little to no direct human evidence that monounsaturated fats (think olive oil) offer a beneficial replacement for saturated fats to reduce the risk of CVD.  The recommendations given are based on animal studies, epidemiological studies, and risk factors (cholesterol) and not intervention studies with hard CVD outcomes.

3.  There is no consistent epidemiological evidence that dairy products adversely effect CVD risk and no intervention research indicating that it actually does.  Although I would not have this perception given the nutritional Zeitgeist.  

4.  Research needs to address the role of individual saturated fats in the diet (although whole foods never contain them in isolation).  Single biomarkers for CVD risk, such as LDL, HDL, triglycerides, LDL particle size, and many more, may be insufficient to judge the effects of diet on actual CVD risk (although by my count, most of these markers are adversely affected by refined carbohydrates and unaffected or improved by fat).  Also, genetics appear to play an important role, but there isn't enough data to clarify this role.

     I'm not sure what the impetus was to have all of these researchers convene and address this issue.  I can only imagine (hope?) that it has been the mounting skepticism for the current dietary recommendations given by numerous organizations; and thus, an opportunity to reevaluate the evidence.  I'm happy to see that refined carbohydrates are being put under the microscope not only for obesity, but now also for heart disease.

(Side note:  I'm doing my best to avoid becoming a sarcastic or overtly critical blogger who constantly points out perceived flaws in what I share.  But I have to say that I'm concerned that eight of the eleven organizations that provided (unrestricted) grants were industrial food groups, most of which were dairy groups.)

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