Should doctors demand better data before recommending plant-based diet?

Posted by Daniel Patrick on

Calls to reduce meat consumption is based on weak data and poorly designed studies according to two articles published by Annals of Internal Medicine.

One of the most widely cited and influential medical journals in the world published research pushing back against how we have come to the conclusion that meat is bad and plant-based diets are good. 'The less people know, the more they actually think they know.' For example who doesn't know that meat is bad for you? But is it really? (Ethical and environmental concerns are not considered, but they are mentioned in the editorial)

Researchers concluded:

The magnitude of association between red and processed meat consumption and all-cause mortality and adverse cardiometabolic outcomes is very small, and the evidence is of low certainty.

Researchers elaborated:

We believe our review provides the most up-to-date evidence on the topic and adds to the existing literature by using a more rigorous evaluation of risk of bias and by providing an assessment of certainty of evidence. Our results, as well as those of other reviews of observational studies, contrast with findings from randomized trials, which have failed to demonstrate an effect of lower red and processed meat consumption on cardiometabolic outcomes (8).
Current dietary guidelines recommend limiting red and processed meat consumption (25, 45). Our results, however, demonstrate that the evidence implicating red and processed meat in adverse cardiometabolic outcomes is of low quality; thus, considerable uncertainty remains regarding a causal relationship. Moreover, even if a causal relationship exists, the magnitude of association between red and processed meat consumption and cardiometabolic outcomes is very small.
Reducing the consumption of unprocessed red and processed meat may result in a decrease in risk for cardiometabolic disease and mortality. The magnitude of absolute effect, if indeed it exists, is very small, and the certainty of evidence is low. Findings from our review raise questions regarding whether—on the basis of possible adverse effects on cardiometabolic outcomes—the evidence is sufficient to recommend decreasing consumption of red and processed meat.
An editorial in the same November 2019 issue of Annals of Internal Medicine further argues that 1) Higher-quality interventional studies would be better 2) Despite this lack of consistent evidence, the case has long been made for reducing meat consumption to reduce risk for cardiovascular disease and various cancers. Indeed, reduction of meat intake is generally endorsed in dietary guidelines. 3) It may be time to stop producing observational research in this area 4) It is time to rethink methods for communicating nutritional data that more effectively improve health outcomes.
This is not a case against plant-based diet, or for meat-based diet. This is a case for better science and how it is communicated.



Carroll AE, Doherty TS. Meat Consumption and Health: Food for Thought. Ann Intern Med. 2019;171:767–768. [Epub ahead of print 1 October 2019]. doi: https://doi.org/10.7326/M19-2620

Zeraatkar D, Han MA, Guyatt GH, et al. Red and Processed Meat Consumption and Risk for All-Cause Mortality and Cardiometabolic Outcomes: A Systematic Review and Meta-analysis of Cohort Studies. Ann Intern Med. 2019;171:703–710. [Epub ahead of print 1 October 2019]. doi: https://doi.org/10.7326/M19-0655


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