Saturday, March 24, 2012

Red meat scare

There have been a number of refutations published of the recent "red meat and mortality" study that has garnered so much attention in the press, e.g.
http://www.nytimes.com/2012/03/13/health/research/red-meat-linked-to-cancer-and-heart-disease.html?scp=2&sq=red%20%20meat&st=cse

Most of these analyses have focused on the difficultly, even absurdity, of learning much from observational studies in contrast to real experiments. They emphasize the pitfalls of self-reported dietary data, the small size of the claimed effect, and question the ability of the researchers to control for confounding variables.  A more substantive post by Ned Kock, excerpted below,  reaches some very interesting, tentative, conclusions from some of the same data:
Here are the correlations calculated by WarpPLS, which refer to the graphs above: 0.030 for red meat intake and mortality; 0.607 for diabetes and mortality; and 0.910 for food intake and diabetes. Yes, you read it right, the correlation between red meat intake and mortality is a very low and non-significant 0.030 in this dataset. Not a big surprise when you look at the related HCE graph, with the line going up and down almost at random. Note that I included the quintiles data from both the Health Professionals and Nurses Health samples in one dataset.
Those folks in Q5 had a much higher incidence of diabetes, and yet the increase in mortality for them was significantly lower, in percentage terms. A key difference between Q5 and Q1 being what? The Q5 folks ate a lot more red meat. This looks suspiciously suggestive of a finding that I came across before, based on an analysis of the China Study II data (5). The finding was that animal food consumption (and red meat is an animal food) was protective, actually reducing the negative effect of wheat flour consumption on mortality. That analysis actually suggested that wheat flour consumption may not be so bad if you eat 221 g or more of animal food daily.
http://healthcorrelator.blogspot.com/2012/03/2012-red-meat-mortality-study-arch.html