Archive for the 'Lipid hypothesis' Category

Saturated fat and heart disease: studies old and new

A study appeared this week sure to drive members of the low-fat and vegan tribes sprinting for their Protexid.

Ron Krauss and his group published a paper in the Articles in Press section of the American Journal of Clinical Nutrition (AJCN) stating there is no evidence that saturated fat intake increases the risk for heart disease.  The paper, titled Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease, is not a study per se, but is a meta-analysis, a compilation of numerous studies looking at the relationship between saturated fat intake and the risk for developing heart disease.

As I’ve discussed before on these pages, meta-analyses are not my favorite types of studies.  I’ve attacked them when they’ve been used to ‘prove’ the low-fat diets are better, so I can’t very well embrace meta-analyses when they present a conclusion I agree with.  And I really can’t embrace meta-analyses when they are compilations of observational studies, which are themselves next to worthless.

For those who don’t know, meta-analyses are compilation studies in which researchers comb the medical literature for papers on a particular subject and then combine all the data  from the individual studies together into one large study.  This combining is often done to bring together a collection of studies, none of which contain data that has reached statistical significance, to see if the aggregate of all the data in the studies reaches statistical significance.  I think these types of meta-analyses are highly suspect, because they can lead to conclusions not warranted by the actual data.

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Four patients who changed my life

In the early 1980s MD and I were laboring away in anonymity in our clinics in Little Rock, Arkansas.  By that time I had gone through my thin-to fat-to thin again metamorphosis, and I was starting to treat patients for obesity.  My own transformation had been fairly striking, a fact not lost on many of my overweight patients, a number of whom were seeking my professional advice on treating their own weight problems.  I was still doing a fair amount of general primary care medicine, but more and more of my time was being diverted to helping people lose weight.

When I, myself, had gotten fat, I had tried a few diets that were then being extolled (including the Pritikin diet) and had experienced pretty much the same thing most people did with these diets:  I lost a few pounds, drifted from the diet, and regained the lost weight plus a little.  I then started thinking seriously about obesity as a medical problem, and in an effort to learn all I could about it, I turned to the medical textbooks on my shelves.  Unfortunately, none of them contained any information I found particularly enlightening.  The texts went into great detail about the risks associated with obesity and the many diseases that it either caused or made worse, but, other than recommending caloric restriction, none really discussed the treatment.  None really discussed (at least not to my satisfaction) what happens metabolically that makes people store excess fat.

I next turned to physiology texts, which didn’t help a lot, either.  I then grabbed my old medical school biochemistry textbook (I hadn’t been out of med school all that long at the time, so it was fairly current) and struck gold.  I started tracing out all the pathways for fat storage and noticed that in virtually every one insulin turned up somewhere.  Then I started reading about all the pathways involving insulin and realized that excess insulin had to be the agent driving the storage of excess fat.  I then went back to the physiology texts, reread them in light of my new found knowledge, and discovered that they reinforced what I had learned from the biochemistry text. I just hadn’t realized it, until I had made the insulin connection. (I drew out all the different pathways insulin worked through on piece of paper that we’ve saved, but I can’t lay my hands on it right now.  If I find it, I’ll post it.)

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The Statinator Paradox

Pity the poor lipophobes and statinators.  They’ve just taken another grievous wound to their favorite theory and haven’t even got sense enough to know it.  In fact, not only do they not have sense enough to realize they’ve taken the hit, they’re actually crowing about it.

The current issue of the Journal of the American Medical Association (JAMA) has an article titled Trends in High Levels of Low-Density Lipoprotein Cholesterol in the United States, 1999-2006 that puts another major dent in whatever validity remains of the lipid hypothesis of heart disease.

I’m going to start categorizing the types of findings published in this paper under the rubric of The Statinator Paradox.  I find it interesting that whenever scientists discover data that shows the opposite of what their hypotheses predict, they don’t conclude that their hypotheses might be wrong; instead they deem the contradiction a ‘paradox’ and bumble on ahead with their hypotheses intact.

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Statinators spill the beans

Oftentimes people become so fixed in their thinking – and in their belief that everyone else thinks the same way – that they unwittingly raise the curtain and expose the wizard of their flawed thinking, showing it for what it really is.  Statinators have done just that in an article in the current issue of the Journal of the American College of Cardiology (JACC).

The study, Effects of High-Dose Modified-Release Nicotinic Acid on Atherosclerosis and Vascular Function, compares the increase in carotid artery plaque over a 12-month period in subjects taking niacin versus those taking a placebo.  It turns out that those subjects taking the niacin experienced a shrinkage of their plaque whereas plaque grew larger on those taking the placebo. The revealing hitch in this study is that both groups were on statins, which means the group on statins alone was the placebo group.  Therefore the data from this study shows that statins alone do not reverse the growth of plaque (at least not plaque in the carotid arteries) despite lowering LDL levels.  Taking the logic a little further, the data from this study gives weight to the idea that a lowered LDL doesn’t reduce plaque growth.

There is a lot we can glean from this study and the from the authors’ commentary on it.

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