Let's start with Big Picture context. I tend to forget sometimes that thoughtful and well-meaning people still believe that Animal Fat is Bad and Simple Carbs are Bad and that we should all be eating cardboard (er, I mean fiber-rich foods), skim milk, olive oil (in moderation), and skinless chicken breasts. I'm also perhaps a little too comfortable with the fact that not only do thoughtful and well-meaning people have that view, but that they think my view (that Animal Fat is Good and Macronutrients Aren't as Important as You Think Absent Insulin Resistance or Other Issues Such as Dementia In Which Case You Should Be Eating More Fat) is lunacy. I mean, my kids get whole milk yogurt still, and they are both over two, the age when fat becomes Bad according to the USDA. (Okay, I'll stop with the capital letters now…)
Part of the reason that I'm comfortable being thought a lunatic is that I think most people secretly believe psychiatrists are lunatics anyway. There is almost always a bit of a double-take when I tell people my profession. In medical circles, I will get a "oh, she's one of those" sort of look. Among lay folk (at a party, for example), people will suddenly clam up or begin telling me their life stories and all about the different psychiatric medicines they've tried. Psychiatrists are a bit of a puzzle - what is it we do, anyway? I think of what psychiatrists do thusly: we look at big, complex puzzles comprised of experience, world view, psychology, environment, and biology and try to figure out how to help someone (typically presenting with emotional issues, though this day and age it could be anything) manage all the factors that could be contributing to the problem. That holistic view of problem-solving health problems makes a psychiatrist somewhat uniquely suited to examining Evolutionary Medicine, but perhaps that is my bias. :-)
Speaking of bias, this week I read with great interest (as always) Paul and Shou-Ching Jaminet's Perfect Health Diet blog, particularly Blood Lipids and Infectious Disease Part 1. In the comments I linked to an commentary on a study about cholesterol and all-cause mortality in Honolulu from the Lancet, the money quote being here:
Sir—The central, surprising, finding from our study was that low serum cholesterol, persisting for 20 years, increased subsequent all-cause mortality. We have no logical explanation for this finding, nor, apparently, do any of our correspondents.
Here is a graph of their data.
And another money quote (these are both from the author's letter replying to other commentary about the findings):
We agree that the association between low cholesterol and mortality is only that; we are sorry that Cuchel and Rader infer a causal relation, since that was not our intent.Yes, a correlation is merely a correlation. But when correlations are always pretty darn consistent (and the most recent PHD post links to 50 studies showing the same correlation, especially true in the elderly), it is important to put our thinking caps on and try to figure out why (correlatively-speaking) higher cholesterol doesn't seem to be killing people as fast as having low cholesterol does, despite the fact that health-minded people have been busy eating good diets and taking meds to lower that cholesterol for a generation. Instead of putting on the thinking caps, the researchers in the Lancet conclude "we have no logical explanation" and timidly suggest that the elderly not be treated quite so aggressively with cholesterol-lowering medications. Which is nice and conservative of them, and fine, but how about a sentence with some thought about why cholesterol might be good for us, since our bodies go through all that trouble to make it, after all, and how we might go about proving causality from these correlations?
So, with the world view of the conventional nutritional researcher firmly in mind, let's go back and look at the Diet and Dementia paper and the actual diets.
A reminder, in this study, 20 healthy older adults (mean age 69) and 29 adults with mild cognitive impairment (mean age about 68) were put on a LOW (low fat, low glycemic carbohydrate) diet or a HIGH (high fat, high saturated fat, high glycemic carbohydrate) diet for 4 weeks. A number of biomarkers related to cholesterol and dementia were measured, and the researchers felt it came out as a clear win for the LOW diet.
I listed most of the results in my previous post, and what I think is the most interesting finding of the paper is how the mild cognitive impairment patients responded quite differently (typically, in more extreme fluctuations of biomarkers, and sometimes opposite trends) to the dietary changes than the healthy controls. For simplicity's sake, I will focus just on the mild cognitive impairment patients in this post.
First, more details about the diets, about which we were told the macronutrient ratios and the fact that food was delivered twice-weekly to the participants. Here was my question to the researchers:
And the initial reply:
The researcher cc'd the nutritionist from the study, who very helpfully took time out of her day to send me a sample day's menu and some more about the methods.