Q. I read that Harvard researchers found no association between eating red meat and developing heart disease and diabetes. Have I been depriving myself of steak for more than 20 years for no good reason?
A. In 2011 some of my colleagues at the Harvard School of Public Health reported findings from a meta-analysis that summarized the results of 20 studies. You're right: they didn't find an association between consumption of unprocessed red meat and heart disease and diabetes. On the other hand, one serving per day of processed meat was associated with a higher risk of developing those diseases. In this and other studies, red meat is defined as beef (including hamburger), lamb, pork, and game, and processed meat as any meat preserved by smoking, curing, salting, or chemicals, which would include bacon, hot dogs, sausage, and cold cuts. The processed meat was primarily processed red meat, but in some of the studies in the meta-analysis, poultry cold cuts were also included in the processed meat category.
There were important — and unavoidable — limitations to my colleagues' meta-analysis. Only a handful of small studies broke out unprocessed red meat separately, so the conclusions were based on just a minor fraction of the data. Furthermore, most of the studies compared calories from red meat to calories from the rest of the diet, which tended to be heavy on refined starch, sugar, potatoes, and, until recently, hydrogenated vegetable oils that contain trans fat. So red meat's lack of association with heart disease and diabetes may only mean that it's just as bad for you as those other unhealthful foods.
Our group in the nutrition department reported findings in 2010 that compared red meat with other protein sources, and it was clear that replacing red meat with chicken, fish, and nuts is associated with a lower risk of heart disease. So I don't think that curbing your appetite for steak was for naught. You improved your chances of not having a heart attack if you replaced it with these healthier options.