Thursday, January 5, 2012

"Saturated Fat And Cardiovascular Disease"

Saturated fat and cardiovascular disease: The discrepancy between the scientific literature and dietary advice:

"Given the large social impact of dietary advice, it is important that the advice have a solid scientific basis. Evidence-based dietary advice should be built on results from all studies available, according to a given methodology. Conclusions should be a valid representation of the summarized results.  
"The association between saturated fat intake and cardiovascular disease was examined.  
"Results from three reports of leading U.S. and European advisory committees were compared with results as they were presented in the articles referred to. Findings were put into perspective with results not included in these reports. Different lines of evidence were included in the different reports. No overlap whatsoever was found in the articles included.  
"Most results from the scientific literature were lacking for most different lines of evidence in all reports. All three reports included the effect of saturated fat on low-density lipoprotein cholesterol in the evidence linking saturated fat to cardiovascular disease, but the effect on high-density lipoprotein cholesterol was systematically ignored.  
"Both U.S. reports failed to correctly describe the results from the prospective studies.  
"Results and conclusions about saturated fat intake in relation to cardiovascular disease, from leading advisory committees, do not reflect the available scientific literature."
I don't have access to the full paper, unfortunately.  But it's pretty clear that the dietary advice has been more concerned with ass-covering than health of late.

Here's a little more from Mr. Hoenselaar:
"...In conclusion, Pedersen et al. do not consider the effect of [Saturated Fatty Acids] on [High Density Lipoprotein]-cholesterol ["good" cholesterol] when examining its effect on CHD risk and they do not mention that results from controlled trials replacing SFA by [Poly-Unsaturated FA] have been consistently biased by a concomitant decline in [Trans-FA] intake. 
"Because prospective cohort studies showed null results from SFA intake on CHD, these results were omitted when judging the evidence for this association. Instead, the authors turned to correlations found in apparently randomly selected ecological studies. No systematic evaluations were made here, and no evidence was presented that the presumed decrease in SFA intakes over the last 30 years contributed to a decline in CVD mortality. While the authors were able to define the possible errors found in prospective cohort studies, no such evaluation was made for the ecological data. Public health recommendations should be based on a transparent evaluation of the lines of evidence included to judge the evidence for an association. In addition, results from these lines of evidence should be judged after systematically reviewing the available literature. 
"Robert Hoenselaar is a student at the High School of Arnhem and Nijmegen, The Netherlands. There is no conflict of interest. The research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors."

And here's the response:

"...Hoenselaar’s questions reflect some of the difficult problems in evaluating the multiple contributors to the complex processes underlying CVD, and CHD in particular. This was highlighted in a previous editorial which illustrates that an understanding of the CHD epidemic requires that all forms of evidence have to be taken into account(19). This also includes multiple consistent ecological data relating to welldocumented diets and CHD rates in many countries. This evidence should not be set aside in analyses. Dietary behaviour is complex and trials that select aspects of diet in isolation are fraught with difficulties of interpretation in a public-health context. As one component of diet changes very often, other aspects also change; imputing causality to only one of these changes can be difficult. Although we do realise the weaknesses of the ecological studies and their possibility of bias, they do provide important insights into population trends in diet and disease patterns over time, and provide a national perspective of the potential impact of multiple changes and prevailing dietary patterns in a societal context, which is the key perspective required in public health."
Insights, but not a cause-and-effect relationship.  Too many variables change to allow firm conclusions from epidemiological ("ecological") data...

I'd say this round goes to Mr. Hoenselaar.  Correlations do not trump non-results from prospective studies, no matter how one would like them to...

P.S.  See this post ("Veggie Oils and Heart Disease") also.  Hoenselaar is channelling Guyenet.

P.P.S.  Turns out Hoenselaar is 37 years old.  And he has a web site: Cancer and Diet.