Don’t trust those reports: Red meat is not good for you

Originally published in the San Francisco Chronicle

Is it safe to eat red meat again? Meat-lovers are licking their chops over recent news coverage suggesting that red meat might not be as bad as we thought. Unfortunately, the headlines have been based on studies that really don’t offer much cover for red meat. I explain why here, making the case in more detail in the current issue of Journal of the San Francisco/Marin Medical Society.

In a group of studies published in the Annals of Internal Medicine, researchers analyzed previous studies in an effort to gauge the strength of the existing evidence against red meat. But the authors end up making recommendations that are at odds with their own findings.

The authors compiled the findings of published studies on red meat to lay out how much benefit a person is likely to get from cutting back on red meat. They estimated that eating three fewer servings of red meat per week was associated with a 7 percent lower rate of death when all causes of mortality are included. Their calculations suggest that cutting out a serving of red meat every day would correspond to a 16 percent drop in all-cause mortality. The authors — astoundingly — conclude that these numbers are too small to justify advising Americans to cut back on red meat.

There are few interventions in medicine that show a measurable effect on death from all causes. A medication or practice that works miracles for one illness still barely moves the needle when measured against all deaths. Yet here is a dietary change that could lead to a 16 percent reduction in total mortality, and the authors call it a small effect!

The authors also disparage the quality of evidence offered in the studies they analyzed. The studies were almost all cohort studies, in which researchers ask people about their diets and track subsequent illnesses and deaths over time. Cohort studies are not as rigorous as randomized trials – often used to evaluate new drugs – where half of patients get a drug and the other half a placebo. On this basis, the authors labels the nutritional cohort studies as “low” or “very low” quality evidence.

But dietary habits and drugs are different, and the studies that examine them ask different questions and face different constraints. Randomized trials are generally not feasible to look at diet over time. Researchers have for many years judged cohort studies to be perfectly acceptable for making recommendations related to diet and nutrition.

Regardless of the link between red meat and overall mortality, there is still a persuasive case to recommend that people reduce red meat consumption. That case is climate change. Red meat is a major contributor to the climate change that threatens the fundamental bases of human health, including survivable temperatures, clean air and water, and the control of infectious diseases.

Recent events in the beef-exporting country of Australia offer a clear warning. As Australia lumbered through a severe drought towards its current catastrophic fires, its many cows continued to consume, on average, around 50 liters of water per day and to produce greenhouse gases at an astonishing rate.

Sometimes where there’s smoke, there’s fire, and such is the case when it comes to the dangers of eating red meat. We can’t afford to keep rehashing this debate.