"The Red Meat Controversy"
The evidence has been building over the last two decades that there is some possible risk from red and processed meat with regards to cardiovascular risk, cancer risk, and overall mortality. However, as we have discussed here previously, the evidence has always been weak.
This controversy has been flamed by a new study published in The Annals of Internal Medicine. The study is actually five parallel systematic reviews, four looking at health outcomes of eating red and processed meat, and one looking at people’s values regarding meat consumption. The paper is the result of a consortium put together for this purpose, with careful vetting to minimize conflicts of interests, and with a 14-person panel voting on final recommendations. They write:
These recommendations are, however, primarily based on observational studies that are at high risk for confounding and thus are limited in establishing causal inferences, nor do they report the absolute magnitude of any possible effects.
They make the “weak” recommendation (based on low to very low quality evidence) that people not change their current eating habits with respect to red and processed meat, specifically because:
- randomized controlled trials > observational studies.
- limited quality of overall evidence; small absolute effect sizes, and limited statistically significant outcomes.
Dose–response meta-analysis results (23 cohort studies, 1.4 million participants) provided low-certainty evidence that decreasing unprocessed red meat intake may result in a small reduction in the risk for major cardiovascular outcomes and type 2 diabetes (between 1 to 6 fewer events per 1000 persons with a decrease of 3 servings/wk).
Dose–response meta-analysis results (17 cohorts, 2.2 million participants) provided low-certainty evidence that decreasing unprocessed red meat intake may result in a very small reduction of overall lifetime cancer mortality (7 fewer events per 1000 persons with a decrease of 3 servings/wk).
So really the conclusion of the authors is not that there is no health risk from red or processed meat. Their conclusion is that we don’t really know as the quality of the evidence is simply too weak to form any confident recommendations. We need better quality data, and we are unlikely to get it - we simply cannot do the large, long term, randomized controlled trials, so we are stuck with the limitations of observational data and the difficulty of controlling experimentally what people eat.
(However) there is good evidence that it is important to health to eat plenty of vegetables, so if you eat a lot of meat you are probably not eating enough plants. The better recommendation, may not be to avoid meat, but to make sure you get enough variety in your diet overall, including plenty of fruits and vegetables.
To me, this article reads as if the author at SBM.com is writing for his audience, coming down on the side of: keep eating meat. This is despite his acknowledgement of:
- the evidence is weak, but it's as good as we can get (due to the very nature of nutrition science).
- avoiding meats could prevent 1-7 serious health events per 1000 people (which is a lot of people in a large population).
- if you eat lots of meat, it's likely you're not eating enough fruits & veg.
- and the stronger evidence against processed meats is ignored (which even the W.H.O. says is best avoided).
If you then include all the environmental benefits to the planet, it's difficult to argue that we should be eating much (if any) meat at all.