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How Unhealthy are Red and Processed Meat?

Summary:
A large share of articles on diet and health read as if good health were people’s only objective. But almost all of us eat things we believe are bad for us because they are very tasty. I have done my best to convince you, my readers, that on any ordinary day, sugar just isn’t worth it, despite how delicious it is. What about red and processed meat? Are they bad enough that you should stay away from them? Worrying about animal welfare or the effects of animal husbandry on climate change could easily tip the balance toward being a vegetarian or vegan. What follows is for those whose main concern about meat is its effects on their own health.

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How Unhealthy are Red and Processed Meat?

A large share of articles on diet and health read as if good health were people’s only objective. But almost all of us eat things we believe are bad for us because they are very tasty. I have done my best to convince you, my readers, that on any ordinary day, sugar just isn’t worth it, despite how delicious it is. What about red and processed meat? Are they bad enough that you should stay away from them?

Worrying about animal welfare or the effects of animal husbandry on climate change could easily tip the balance toward being a vegetarian or vegan. What follows is for those whose main concern about meat is its effects on their own health.

Using panels of lay-people as well as experts in order to judge any harm of meat-eating in comparison to the pleasure from meat-eating, the article shown above, “Unprocessed Red Meat and Processed Meat Consumption: Dietary Guideline Recommendations From the Nutritional Recommendations (NutriRECS) Consortium” by Bradley C. Johnston et al. says you don’t need to change your meat-eating habits. I come down more toward advice to eat meat quite sparingly. Let me lay out the views of Bradley C. Johnston et al. and my reaction.

A Summary of Evidence on the Health Effects of Meat Eating

The key to the recommendation of the panels organized by Bradley C. Johnston et al. is the summary of the scientific evidence, which boils down to saying the health benefits from a substantial reduction in meat consumption are likely to be quite modest. To make the summary of evidence easier to read, let me put their words verbatim into bullet points and omit the references they give—and their mention of results for dietary patterns correlated with, but not specific to meat. In the subsection “Evidence Summary for Harms and Benefits of Unprocessed Red Meat Consumption,” they say:

  • For our review of randomized trials on harms and benefits (12 unique trials enrolling 54 000 participants), we found low- to very low-certainty evidence that diets lower in unprocessed red meat may have little or no effect on the risk for major cardiometabolic outcomes and cancer mortality and incidence.

  • Dose–response meta-analysis results from 23 cohort studies with 1.4 million participants provided low- to very low-certainty evidence that decreasing unprocessed red meat intake may result in a very small reduction in the risk for major cardiovascular outcomes (cardiovascular disease, stroke, and myocardial infarction) and type 2 diabetes (range, 1 fewer to 6 fewer events per 1000 persons with a decrease of 3 servings/wk), with no statistically significant differences in 2 additional outcomes (all-cause mortality and cardiovascular mortality).

  • Dose–response meta-analysis results from 17 cohorts with 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), with no statistically significant differences for 8 additional cancer outcomes (prostate cancer mortality and the incidence of overall, breast, colorectal, esophageal, gastric, pancreatic, and prostate cancer).

In the subsection “Evidence Summary for Harms and Benefits for Processed Meat,” they say:

  • No randomized trials differed by a gradient of 1 serving/wk for our target outcomes.

  • With respect to cohorts addressing adverse cardiometabolic outcomes (10 cohort studies with 778 000 participants providing dose–response meta-analysis), we found low- to very low-certainty evidence that decreased intake of processed meat was associated with a very small reduced risk for major morbid cardiometabolic outcomes, including all-cause mortality, cardiovascular mortality, stroke, myocardial infarction, and type 2 diabetes (range, 1 fewer to 12 fewer events per 1000 persons with a decrease of 3 servings/wk), with no statistically significant difference in 1 additional outcome (cardiovascular disease).

  • For cohort studies addressing adverse cancer outcomes (31 cohorts with 3.5 million participants providing data for our dose–response analysis), we also found low- to very low-certainty evidence that a decreased intake of processed meat was associated with a very small absolute risk reduction in overall lifetime cancer mortality; prostate cancer mortality; and the incidence of esophageal, colorectal, and breast cancer (range, 1 fewer to 8 fewer events per 1000 persons with a decrease of 3 servings/wk), with no statistically significant differences in incidence or mortality for 12 additional cancer outcomes (colorectal, gastric, and pancreatic cancer mortality; overall, endometrial, gastric, hepatic, small intestinal, oral, ovarian, pancreatic, and prostate cancer incidence).

Bradley C. Johnston et al. note that results look stronger for dietary patterns correlated with meat-eating than when looking specifically at meat-eating. This calls into question whether meat-eating itself is a problem as opposed to something else that meat-eaters on average tend to do more than others—beyond eating meat.

My Reaction to “Unprocessed Red Meat and Processed Meat Consumption: Dietary Guideline Recommendations From the Nutritional Recommendations (NutriRECS) Consortium”

As I say in

I worry that animal protein is especially nutritious for cancer cells. But the short version of that story is that sugar and certain amino acids, such as glycine, are especially easy for cancer cells to metabolize. If you keep your consumption of both animal protein and sugar very low, it will make it very hard on cancer cells and pre-cancerous cells. But cutting animal protein consumption in half while continuing sugar consumption full-speed may not put that much stress on cancer cells and pre-cancerous cells.

The bottom line of this logic is that cutting back on meat consumption may have a much bigger positive health effect for those who have gone off sugar than for those who haven’t. Unfortunately, few enough people have gone off sugar that the bulk of the evidence discussed by Bradley C. Johnston et al. doesn’t speak to this possibility.

Moreover, if you have gone off sugar, then when you eat meat might have just as big an effect as the total amount. Occasional meals with a lot of meat with a week or two going by with not meat might be much harder on cancer cells and pre-cancerous cells than eating the same amount of meat a little each day to keep the cancer cells and pre-cancerous cells going.

I know a lot less about how animal protein affects cardiovascular outcomes, if you do want to continue eating meat, it is worth knowing that fasting—a period of time with no food (but continuing to drink water)—gives your body a chance to repair itself, taking apart defective cells and using the parts for other cells that are in better shape. A lot isn’t known, but to me that makes it sound hopeful that damage that has already been done might be repaired if you make fasting part of your regimen. On fasting, see:

Conclusion

Bradley C. Johnston et al. effectively provide reasons why if you are only worried about the effects on your health you should consider going off sugar (and other easily digestible carbs such as potatoes, rice and bread) a higher priority than reducing red and processed meat consumption. But once you have managed to go off sugar, I recommend that you don’t eat meat every day. And it is likely to be a good idea to have days when you refrain completely from eating any animal products, or go beyond that and fast.

For annotated links to other posts on diet and health, see:

Miles Kimball
Miles Kimball is Professor of Economics and Survey Research at the University of Michigan. Politically, Miles is an independent who grew up in an apolitical family. He holds many strong opinions—open to revision in response to cogent arguments—that do not line up neatly with either the Republican or Democratic Party.

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