Carnivore

This is a excellent response article, and deserves to be read in its entirety, its comprehensive and elegant.

My notes from my read through.

These data are, for the largest part, generated from observational studies within the domain of nutritional epidemiology, the limitations of which will be discussed below.

Taken together, it is repeatedly stated in academic literature that high meat intake is associated with higher mortality, cardiometabolic illnesses, diverse types of cancer, and intestinal disorders

make recommendations based on this research, assuming causal relationships between meat intake and morbidity and mortality

overwhelming corpus of often non-robust and overstated observational findings has been amassing over the last decades in the field of nutrition. Naïve interpretations of these findings are often promoted by the media and influence nutritional guidelines.

The input data obtained from food frequency questionnaires should be interpreted prudently as they can be problematic for a variety of reasons

Social desirability bias in food reporting is just one example, as reported consumption can be affected by the perceived health status of certain foods. Not all self-defined vegetarians avoid meat, which is suggestive of a considerable risk for underreported intake in health-conscious groups

diets are difficult to disentangle from other lifestyle factors. It has been shown that Western-style meat eating is closely associated with nutrient-poor diets, obesity, smoking, and limited physical activity. Given the fact that health authorities have been intensely promoting the view that meat is unhealthy, health-conscious people may be inclined to reduce intake.

i.e. Healthy Subject confounders.

Typically, the associations between meat eating and disease tend to be higher in North American than in European or Asian cohort studies, indicating the presence of lifestyle bias and the need for cross-cultural assessments

Likewise, when omitting Seventh-Day Adventist studies from meta-analyses, the beneficial associations with cardiovascular health for vegetarian diets are either less pronounced or absent indicating the specific effects of health-conscious lifestyle rather than low meat consumption as such. This is important, as Seventh-Day Adventism has had considerable influence on dietary advice worldwide

Third point, the relative risks (RRs) obtained from observational studies are generally low, i.e., much below 2.

such low RR levels in isolation would not be treated as strong evidence in most epidemiological research outside nutrition

ex… The association between meat eating and colorectal cancer, for instance, leads to an RR estimate below 1.2, whereas for the association between visceral fat and colorectal neoplasia this value equals 5.9. The latter provides a robust case that is much more deserving of priority treatment in health policy development

Nutritional epidemiology is a useful tool for the generation of hypotheses, but its findings as such do not provide a robust basis for the implementation of health policies in the absence of further substantiation. Or, as stated by Gerstein et al. (2019), “analyses of most observational data from the real world, regardless of their sophistication, can only be viewed as hypothesis generating”

the current epidemiological and mechanistic data have not been able to demonstrate a consistent causal link between red meat intake and chronic diseases, such as colorectal cancer

Intervention studies that overlook the normal dietary context or use non-robust biomarkers should be interpreted with caution, and do not justify claims that there is a clear link between meat and negative health outcomes

i.e. RCTs that look at health markers like LDL instead of hard endpoints like all cause mortality

we conclude that there is a lack of robust evidence to confirm an unambiguous mechanistic link between meat eating as part of a healthy diet and the development of Western diseases. It is paramount that the available evidence is graded prior to developing policies and guidelines, making use of quality systems such as GRADE

i.e. Make drastic changes AFTER you have data, not before, or we will repeat the low-fat problem Ansiel Keys created in the 1950s - which also was introduced before data was available.

3.3. A scientific assessment should not overlook conflicting data…Dietary advice that identifies meat as an intrinsic cause of chronic diseases often seems to suffer from cherry-picking

Whereas per capita consumption of meat has been dropping over the last decades in the US, cardiometabolic diseases such as type-2 diabetes have been rapidly increasing. Although this observation does not resolve the question of causality one way or the other, it should generate some skepticism that meat is the culprit

We contend that a large part of the case against meat is based on cherry-picked evidence and low-quality observational studies. The bald claim that red meat is an “unhealthy food” (Willett et al., 2019) is wildly unsupported.