A new analysis of the PURE study published in the American Journal of Clinical Nutrition reports no association between eating red meat and the risk of early death, heart disease, cancer, or stroke. Does this study completely clear red meat's reputation?
The short answer? It does, and it doesn't.
Here's why the study doesn't mean red meat is "innocent": This analysis is still a low-quality nutritional epidemiology study that can't prove cause and effect. The study can't "prove" red meat doesn't increase risk, but it can certainly suggest it.
Here's why it might show red meat is "innocent": This study did not appear to have the usual "healthy user bias" among the different groups of meat-eaters and found a beneficial result to red meat.
What do I mean by that? As we've written about before, in many concerning observational studies about red meat, those who ate more red meat were overall less healthy. They consumed more calories, smoked more, drank more alcohol, and exercised less. Also, they had different socioeconomic backgrounds; they were less educated, made less money, and were more likely to be men.
Just as we can't conclude that eating more meat caused them to smoke or be less educated, we also can't conclude that eating more meat caused them to get heart disease or diabetes.
But the PURE results did not suffer from the same dramatic difference in baseline characteristics between the meat-eating and non-meat-eating participants. Perhaps the multinational population in this study canceled out the inherent healthy user bias that occurs in Western societies.
Additionally, when a sizeable observational study fails to find a harmful association between red meat and heart disease or cancer, it calls into question the other studies that found a minimal increased risk. How significant can the risk be if a large study, like the one from PURE, didn't detect any risk?
The risk can't be very significant - if it exists at all.
This study did find a small increased risk (hazard ratio ranging between 1.3 to 1.8) of heart disease, cancer, and death for those who ate more than 150 grams per week of processed meat.
Those who ate more processed meat were more likely to be men and live in urban settings, but the baseline characteristics were otherwise similar.
As we wrote about before, the science supporting increased health risk from processed meat is mostly from low-quality studies, and the risk appears to be small.
However, processed meat does seem to have a stronger association than less processed red meat. But whether that is a significant risk remains to be definitively proven.
Along similar lines, a new review of existing systematic reviews, looking at fat intake and health outcomes, was published in Annals of Nutrition and Metabolism. This study concluded:
"(Systematic reviews) found mainly no association of total fat, monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and saturated fatty acid (SFA) with risk of chronic diseases. "
The study also reported:
"A higher intake of total trans-fatty acid (TFA), but not ruminant TFA, was probably associated with an increased risk of mortality and cardiovascular disease based on existing (systematic reviews)."
This means industrially created trans fats - such as margarine, or fats found in fried foods, and baked goods - are worse for you. But natural trans fats - from cows or other animal sources - are not associated with poor health outcomes.
The two published studies provide more evidence that meat or fat may not be the issue. Instead, industrial processing and taking the meat or fat further away from its natural state may be what increases health risk.
If you are a meat lover, eat up! There is no high-level science to suggest you shouldn't. Here are some of our favorite meat recipes to get you started.
Thanks for reading,
Bret Scher, MD FACC
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