That doesn’t mean you can’t eat bacon or pepperoni; that’s up to you. You are the boss. But while everyone is entitled to their favored opinions and choices, not so facts. The facts are the facts, and the facts about processed meat are quite clear. We’ll come back to those and the new study momentarily.
First, I’ve noticed the inevitable during my travels of the past week: a whole lot of anxious conversations about the coronavirus. This is not entirely unfounded- the pandemic is alarming. For those wanting good, up-to-date, expert intelligence about the virus, its spread, the risks, and suitable responses- they are available. We might all take a moment as well to reflect on how preventable such anguish and potential calamity might be if we would ever learn from the follies of history, be pro-active rather than always reactive, and if the court of public opinion reliably honored the brave and convicted the despotic, rather than the currently popular opposite.
My contribution is a reality check about risk. To date, the global death toll from the coronavirus- as I write this- is 638. The risk is not evenly distributed, of course, but if it were, it would at present mean a personal risk of death from this virus of roughly 1 in 12.5 million. If you bank at all on odds like that, do be sure to get your Powerball ticket today.
In contrast, measles, before there was a vaccine introduced in 1963, routinely killed over 2.5 million people a year, most of them children. The most recent statistics, fueled by global gaps in vaccine coverage and anti-vaccine conspiracy theories, are 140,000 deaths, again mostly young children, in 2018. Before the coronavirus is as bad as just a garden-variety-year for measles, it will need to kill 219 people for every one it has killed thus far.
The point here is that when it comes to the assessment of risk, we are, in a word, nincompoops.
We routinely dismiss large risks genuinely likely to impact our lives, and exaggerate risks that are new, newsy, or exotic; we get wildly worked up for a little while about risks that come and go, while cultivating the contempt famously born of familiarity when risks stay and never stop stealing years from lives and life from years. Threats to you and those you love literally orders of magnitude greater than coronavirus don’t just hide in plain sight; you welcome them daily into your family kitchen.
With that in mind, let’s have a look at the new processed meat study, published in JAMA Internal Medicine. The study is of considerable size and careful methods. The associations between meat (especially processed meat) intake and adverse health effects are consistent with virtually all prior research on the topic, including the systematic reviews on which the contrarian, so-called “guidelines” last September were allegedly based. Those studies, too, found statistically significant harm- more death, more heart disease, more cancer, more diabetes- with higher intake of red and processed meat, they just graded certainty in their own findings as low, and chose to recommend...the opposite.
The magnitude of risk increase reported in the new study was relatively small, but as noted above, people worry routinely about risks vanishingly smaller- from plane crashes to sharks to lightning strikes. At the level of just two servings per week, the authors found a roughly 7% increase in the risk of cardiovascular disease with processed meat, and a 3% increase with red meat. The risk of death was increased roughly 3% by both.
Are these really the “modest” risks they are reported to be? Consider that the current risk of death by coronavirus averaged over the global population and expressed as a percent is 0.000008%.
A 3-7% increase in the risk of heart disease or death that is entirely controllable by individual choice- is a very big deal. At the population level of the United States, 3% is 9 million people. For only the population over age 50, it's still well over a million.
Roughly 3 million people die annually in the United States; a relative 3% bump in that figure is an additional 90,000 deaths. Does that sound like a small number- when you start thinking about 90,000 families anguished at the CCU, or grieving at the cemetery? Does that magnitude of unnecessary loss and grief sound...small?
That's the problem with universal exposures like diet and statisticians who forget that behind their “numbers” are actual people. Small shifts in risk at the individual level can add up to enormous differences in public health. There is nothing small about tens of thousands of entirely avoidable deaths or heart attacks every year.
The new study was observational, and those espousing a seemingly religious devotion to the exclusive merits of randomized trials are apt to wave it off accordingly. This, however, is entirely unfounded on the basis of science and sense alike. Most of what we humans know that matters most to making it through any given day- from the dangers of electricity and fire, to those of slippery shower floors or changing lanes in traffic- are entirely observational, and involve no formal studies at all- and certainly none randomized.
The risks of shark attack are vanishingly smaller than those of processed meat, and there are no randomized trials to corroborate them; should we, accordingly, issue guidelines encouraging swimmers to head toward, rather than away from, that ominous dorsal fin slicing the water? The risks of lightning are also vanishingly small compared to all of the above, and again- there are no randomized intervention trials to confirm what we think we know. So, are guidelines justified encouraging people to run around in thunder storms waving long metal poles? For that matter, most people who drink don’t get cirrhosis, and there are no randomized trials affirming the link for those who do. Guidelines, accordingly, to drink up, and livers be damned?
The rebuttal is equally robust from the realm of science. Hormone replacement at menopause was thought good for health based on observational studies, then bad based on randomized trials that seemingly missed baby for bathwater. Both were a bit right and both a bit wrong, and the current understanding, informed by both, is that women can experience net benefit or harm depending on personal circumstances and the specific version of hormones. There is no “one kind” of evidence that owns a monopoly on understanding.
There are some more interesting tidbits from the new study. The authors report that the adverse effects of unprocessed red meat were greater with higher overall diet quality. This is a very important point, easily overlooked.
What it means is that if diet quality is poor overall - few fruits and vegetable, lots of highly processed food, lots of processed meat, lots of added sugar- the adverse effects of red meat are obscured, diminished, or disappear. That is because questions about any given food or food type always come down to: "instead of what?" If everything you eat instead of red meat is bad for you, and red meat is comparably bad for you- it becomes impossible to isolate the adverse effects of red meat.
By way of analogy, running in intense heat without adequate hydration is “bad” for you- but if you are doing that because you and your platoon are ringed by enemy gun fire, a high casualty rate from gun fire will make the ills of dehydration inconsequential. But that doesn't mean they aren't real, or important- it just means they don't matter much, independently, when your overall situation is dire. And let’s be clear, the dietary situation in America is, indeed, dire.
Conversely, even unprocessed red meat was decisively harmful when diet quality was higher. That's because in such a situation, there is still room left for dietary harm to be done- it's not already maxed out. So, yes- relative to eating the more healthful alternatives- even unprocessed red meat is decisively linked to mortality and heart disease. There is just more than one way to eat badly, and substituting one of these for another is a lateral move.
Finally, the authors did a very careful analysis, which is, of course, good. But the reality is, foods are not isolated exposures; they contribute to overall dietary pattern. It is overall dietary pattern, and diet quality, that matter most to health.
People consuming higher levels of processed meat and red meat are, all but inevitably, consuming lesser amounts of the main alternative plant foods- legumes, whole grains, nuts, vegetables, etc. The authors of the new study controlled for these, however. That's arguably a good thing in the service of methodologic purity, if the goal is to isolate the harmful effects directly attributable to meat and processed meat only. But it is also very unrealistic, because that's not how diet works in the real world; more beans means less beef in the real world, more beef means less beans.
What all this means is that the real-world adverse effects of higher intake of processed and red meat are almost certainly, and perhaps very substantially, underestimated by this study. A realistic assessment of the actual risk in practice was sacrificed for a risk estimate that was unassailably defensible because of meticulous controls. No doubt noise will be made about uncertainties in these data- but while true, they almost all point in the direction of actual, real-world risks considerably higher than those reported.
Put this study in the context of all prior research on the topic, and it is a robust affirmation of what we already knew. We can, and should, inform our understanding of what is true, in nutrition and in general, from a variety of evidence sources that make different, but comparably important, contributions to the overall weight of evidence.
It’s been a very long time, but I remember liking the bacon and deli sandwiches I ate as a kid, the charcuterie I tasted when I first visited France. I wish they weren’t bad for me, worse for the planet, and all too often a product of callous cruelty and brutal abuse of our fellow creatures. But they just are. I subordinate the inclinations of taste to those of conscience. It’s easier than you think, because taste buds readily learn to love the foods they’re with. What you choose to do with both native taste and informed conscience is, of course, up to you, but the facts are not. And since there are ever new ways to avoid meat and taste it, too- perhaps there is a new détente possible between the predilections of palate and the relief of conscience.
As you chew on that, be sure to put the risks that compete for your attention into reasonable perspective. Coronavirus is scary, but thus far, very, very unlikely to affect you or anyone you love. Stay tuned, but keep calm and carry on.
Conversely, just try to picture 90,000 variants on the theme of anguish written across the face of wife, husband, daughter, son, sister, brother. You won’t make it through the tiniest fraction of that sum before conceding- there is nothing small about it.
David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and current President of the American College of Lifestyle Medicine. He has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both preventive medicine, and nutrition. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates.