Notes -

Vegetarianism for ethical or religious reasons predates modern history

OR ECONOMIC!!!!!!!!!!!!!!!!!!!!!!!!!! don't forget the most common driver of plant based lifestyles.

Given that a century ago nutrition science was in its infancy, the earliest arguments for the superiority of “meat-free” diets for health were shaped more by religious and moral sentiments than by empirical evidence

Honestly, we haven't improved much since then.

several reports demonstrated that there were no differences in mortality when vegetarians were compared to meat-consumers with similar socio-demographic characteristics

One of the core problems with epidemiology - what you control for, the assumptions you make (and low hazard ratios).

The larger body of evidence suggests that the health benefits associated with vegetarianism may not be due to the avoidance of meat per se, but other “lifestyle” factors associated with socio-economic status, such as adequate levels of physical activity (Archer, Lavie, and Hill Citation2018a), low alcohol and drug consumption (O’Keefe et al. Citation2018), or the avoidance of tobacco products.

And avoiding processed foods, and avoiding processed carbs especially, fructose, etc.

Recent results suggest that individuals who abstain from meat and/or other animal-based foods may suffer from nutritional deficiencies (e.g., vitamins B12 and D, ω‐3 fatty acids, calcium, iron, and zinc; Craig Citation2010; Dwyer Citation1991) with concomitant poorer physical health

Furthermore, there is an emerging body of evidence that meat-abstention is linked to mental disorders and poorer psychological well-being. Specifically, when compared to those who consume meat, vegetarians are more likely to suffer from or be diagnosed with major depression and anxiety, and are more likely to attempt self-harm (e.g., suicide)

In 2010 and 2015, investigators found that with respect to some facets of mental health assessment, vegetarians were healthier than meat-consumers

One big issue is the metabolic context of "meat-consumer" is most likely a 70% pbf carb loading processed food enjoyer, so there are lots of confounders in the comparison of "meat-consumer"

Recently, Johnston et al. and Carroll and Doherty suggested that the evidence supporting public health recommendations to limit or eliminate meat consumption was based on questionable research and “inappropriate analyses”

!!!! takes us right back to the second sentence "superiority of “meat-free” diets for health were shaped more by religious and moral sentiments than by empirical evidence"... epidemiology can be shaped to say what you want it to say, this is why it can't prove cause and effect, its hypothesis generating only.

more importantly, equivocal and potentially biased research on meat-consumption has contributed to the growing confusion and incredulousness surrounding the value of nutrition science

By design! Perhaps people are simply biased, but the overwhelming body of work and repeated use of poor statistical analysis and cherry picking leads me to favor unethical actors then naivety

The extant literature suggests that there are numerous factors that may explain the contradictory associations of meat-abstention and health. These include variations in research design, recruitment and sampling strategies , the disparity between self-reported and actual dietary intake , the lack of validity of assessment protocols or metrics employed for exposures and outcomes (e.g., diagnosed conditions vs. subjective perceptions), and lack of understanding and control for confounding variables and/or effect modifiers.

All problems with the necessary assumptions used in creating epidemiological hypotheses.

Another important and oft-cited factor is the definition and characterization of vegetarians and/or those who abstain from meat consumption . For example, the comprehensive term “vegetarian” may be used to describe individuals who avoid only red meat (e.g., beef), avoid both red and white meat (e.g., pork, poultry) or those who simply consume predominantly plant-based diets. Furthermore, investigators frequently subdivide vegetarians into several groups categorized by the types of foods they exclude. While no definition is definitive and categories vary significantly, “vegans” exclude all foods and beverages derived from animals (e.g., fish, eggs, dairy, or meat) and may also avoid using any animal-based products (e.g., leather clothing). Ovo-lacto vegetarians consume no meat but will eat eggs and dairy, whereas pescatarians eat fish but not red meat or poultry, and flexitarians consume a predominantly plant-based diet while occasionally consuming meat.

These inconsistent and intersecting definitions in concert with self-reported dietary status may lead to misclassification because there is a clear and important distinction between merely reporting that one avoids meat and actual meat-abstention.

However, if you wanted to gerrymander the population to find the outcome you predetermined, this level of flexibility in definition is extremely useful. Most people only read a headline, barely anybody reads abstracts, and no-one actually reads the full papers. Define your language to get the headline you want, and bam.... agenda driven epidemiology

Given the global increase in psychological disorders in concert with increments in the advocacy and practice of vegetarianism, there is a need to clarify the relation between meat-abstention and psychological health.

If only there was some way to examine this correlation

To avoid inconsistent definitions of vegetarianism, our analysis sought to capture studies that clearly differentiated between individuals who reported consuming meat and those reporting to be meat-abstainers, while acknowledging that the overall dietary patterns exhibited by both groups (and most humans) are varied.

!! Good. Sticking to their guns... unlike the plant based paper the other day that included up to 15% meat in the plant based group.... which is already the standard level of meat consumption in the general population....

Therefore, the non-normative dietary exclusions espoused by vegans and strict vegetarians may lead to inflated or illusory rates of psychological dysfunction. For example, it is well-established that vegetarianism may be used as a strategy to mask disordered eating and that the endorsement of vegetarianism is highest in females with severe eating pathology

hrmm

There were numerous issues that reduced the confidence in the published results. As detailed in our discussion, these issues included cross-sectional design, non-representative sampling, biased recruitment, the use of subjective (i.e., self-reported) dietary and psychological data, the failure to account for social desirability and observer-expectancy effects (e.g., reactivity), the failure to collect data on actual dietary intake, and statistical, interpretive, and communication errors such as the failure to correct for multiple comparisons, recognize regression to the mean, and the inappropriate use of causal language.

Indeed, the rigor isn't there.

The most rigorous study reviewed, Michalak, Zhang, and Jacobi (Citation2012), found a clear relation between the avoidance of meat and depression and anxiety in both a representative sample of German adults (n = 4181; including 3872 non-vegetarians and 54 “complete vegetarians”) and a socio-demographically matched subsample of non-vegetarians (n = 242). Meat-abstainers (i.e., “complete vegetarians”) had 1-month, 12-month, and lifetime prevalence of unipolar depressive disorders of 7.4%, 24.1%, and 35.2%, respectively.

35% damn... that is a lot of depression in a population!

They found that the use of prescription medications for depression in women who abstained from meat was nearly twice that of women who ate meat (8.0% vs. 4.2%).

Based on this systematic review comprising 160,257 participants from varied geographic regions, including Europe, Asia, North America, and Oceania, aged 11 to 96 years, there is clear evidence that meat-abstention is associated with higher rates or risk of depression, anxiety, and self-harm.

Indeed, we also see lots of aggressive behavior on lemmy along meat/anti-meat lines - I wonder if they are related? (Just look at the modlog of this community for hundreds of angry sockpuppet downvoting into eternity)

economically disadvantaged individuals who do not consume meat due to its relative cost may be at risk for ill-health for myriad reasons independent of their lack of meat consumption. Thus, future research examining temporal relations should establish clear distinctions between individuals and populations that abstain from meat consumption due to ethical, religious, and health-related perceptions, or those who do not consume meat for economic reasons.

Indeed!

Investigators who seek to over-sample groups that are highly invested (e.g., ethically, socially, intellectually or emotionally) in their “lifestyle” or dietary choices should acquaint themselves with the large body of research on cognitive dissonance, social-desirability , and observer-expectancy effects (e.g., reactivity).

Academic Burn, honestly the journals and peer reviewers should have caught this too!