If you're a dedicated carnivore, as Rick admits he is in this week's PodMed, you won't welcome this week's Archives of Internal Medicine study 'Red Meat Consumption and Mortality,' gleaned from two huge studies of healthcare professionals, the Health Professionals Follow-Up Study, and the Nurses Health Study. Taken together, these two studies represent data from over 120,000 people observed over 20 years. Yowl. That's a lot of number crunching, and it clearly points to the conclusion that eating red meat increases mortality and cancer risk. Salmon, anyone?
So how did the investigators reach this rather unpopular conclusion? It's worth looking at the study populations to gain an historical perspective. The Health Professionals Follow-up Study enrolled over 50,000 male physicians, dentists, pharmacists, and other health professionals aged 40-75 years and began in 1986. The Nurses Health Study enrolled over 120,000 female nurses (my mother among them!) aged 30-55 years and began in 1976. All subjects were queried rather extensively and this analysis looks at food questionnaire data gathered every two years. What's amazing is that over 90% of participants returned these questionnaires, an enviable response rate, as any researcher employing this method of surveying subjects will agree. And while anyone self-reporting anything is subject to recall bias, it's probably safe to assume that these subjects had more knowledge and appreciation than most of the import of their responses, so would hopefully err on the side of frankness.
People who had pre-existing heart disease or cancer were excluded from this analysis, as were a number of others for a variety of reasons. The final analysis had a robust 121,342 subjects. They were queried on their consumption of unprocessed red meat, which included lamb, beef or pork, and processed red meats, including hot dogs, bacon, sausage, salami, bologna and other processed meats.
Information on lifestyle and medical factors was updated every two years. Cigarette smoking status, body weight, physical activity level, medication use, supplement use, and both family history or personal development of heart disease, diabetes or high cholesterol was also obtained. Death data was collected as well.
After controlling for these and other factors, the relationship between both increased mortality and cancer risk relative to red meat consumption remained. While this risk was not huge, it was present even after correcting for possible confounders, and it was (as would likely be predicted) greater for processed meats than for unprocessed meats. So what's a devoted meat eater to do?
The researchers went to the trouble of calculating risk reduction with substitution of other foods for just some of the meat, and this did have an impact. Perhaps that is part of the answer then: not no meat, but simply less. The authors also speculate on what exactly is it about red meat that accounts for the increased risk, and were not able to clearly finger the obvious villains of iron or fat. Clearly that's a subject for further study.
Other topics this week include an Agency for Healthcare Research and Quality assessment on drug and non-drug management of urinary incontinence in women, partially published in Annals of Internal Medicine, a look at the predictive value of EKG abnormalities in JAMA, and also in Archives, a study of methods of colorectal cancer screening and adherence. Until next week, y'all live well.