Harvard Health Letter

Can you explain the red meat debate?

Ask the doctor

Q. Just before the holidays, I heard that a study said it was okay to eat red meat. Previously, you’ve said just the opposite. Help!

A. We got lots of letters like yours. The bottom line is that we stick by our longstanding advice: avoid frequent meals of red meat, and especially processed meat.

Most of the studies that have been done to determine the effects of nutrition on health are called observational studies: large numbers of people are followed for decades, and they record what they eat and what illnesses they experience.

The weakness of observational studies is this: if you find, for example, that people who eat more red meat also have more heart attacks, you can’t be sure that there’s not some other factor besides red meat that caused their heart attacks. But statistical techniques can account for the effect such factors might have.

The recent controversy was caused by a self-appointed panel (only two members of which described themselves as true nutrition experts) that pulled together the results of over 100 previously published studies involving six million people.

The studies actually did show that people who ate less red meat and processed meat had significantly lower rates of diabetes, heart disease, and cancer, and lower rates of death from heart disease and cancer. But since the panelists regarded observational studies as “weak,” they didn’t put much credence in those findings. Also, they argued that the heart disease rates were not that much lower in meat avoiders.

However, if you apply the numbers they came up with to the entire population of the United States, it comes to an awful lot of people who wouldn’t get heart disease if they avoided meat.

When it comes to nutrition, the best kind of study would be a randomized controlled trial (RCT) in which people are assigned at random to eat one type of diet or another. This is really hard to do. Imagine telling a thousand people to eat red meat on a regular basis for 20 years, and another thousand to avoid red meat every day for 20 years—and imagine monitoring them for 20 years to be sure they ate as you wanted them to. Pretty hard to pull that study off, right?

There is one large RCT of the fats in red and processed meat that found no connection to heart disease, but in my opinion this study didn’t follow enough people for long enough to get definitive results.

In short, I don’t think these studies provide a reason to change our advice to minimize eating red meat and processed meat. I have red meat at most one or two times a week, and processed meat rarely—like a hot dog on the Fourth of July.

— by Anthony L. Komaroff, M.D.
Editor in Chief, Harvard Health Letter

Image: bhofack2/Getty Images

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