March 25, 2025, 2:16 pm | Read time: 6 minutes
More and more people are reducing their meat consumption — for health, ethical, or ecological reasons. A new meta-analysis wanted to find out whether there is a connection between meat consumption and mental health. The results actually suggest that there is.
An international group of researchers from the University of Granada has carried out a comprehensive systematic review and meta-analysis. The study, published in the journal Nutrients, aimed to determine if individuals who abstain from meat or consume it in minimal amounts have an increased or decreased risk of depression. The question of whether psychosocial factors play a role was also particularly important.1
Overview
- What Was Investigated
- How the Researchers Proceeded
- Result: Meat-Free Diet Associated with Lower Likelihood of Depression
- Meat-Free Diet and Development of Depression — These Factors Could Play a Role
- Classification of the Study and Possible Limitations
- Conclusion on the Link Between a Meat-Free Diet and Depression
- Sources
What Was Investigated
The discussion regarding the connection between diet and mental health is not a new one. While some studies suggest that abstaining from meat could increase the risk of depression, others show the opposite. This could be due to methodological differences or psychosocial factors that were not taken into account. A major problem in previous studies has also been the question of which comes first: do people eat less meat because they suffer from depression? Or is the risk of depression lower because they are on a meat-free diet.2,3
The Spanish researchers’ decision to only consider long-term studies now served to reduce this uncertainty somewhat.
How the Researchers Proceeded
As already mentioned, the meta-analysis focused exclusively on long-term studies in which people were followed over several years. In total, the study included 20 samples from 17 long-term studies published between 2009 and 2021 with 64,992 participants.
They used the so-called Newcastle-Ottawa Scale (NOS) to assess study quality. This method awards points for criteria such as the selection of study participants, the accuracy of the measurements, and the consideration of confounding factors (e.g., age, social environment).
The more points a study received, the higher its quality was rated. Social factors such as education, income, and gender were also included in the analysis.
Result: Meat-Free Diet Associated with Lower Likelihood of Depression
The meta-analysis showed a correlation that suggests that a meat-free diet could be associated with a lower risk of depression. People who completely abstained from meat had a hazard ratio (HR) of 0.74. This means that depression occurred less frequently or later in this group than in meat eaters. An HR of 0.74 corresponds to a 26 percent lower probability of developing depression during the observation period.
However, the evidence for a flexitarian diet, in which meat consumption is severely restricted but not completely excluded, was less clear. Here, the HR was 0.90, i.e., a 10 percent lower probability of depression, and the results varied depending on the group studied.
The researchers also found moderate heterogeneity between the studies analyzed. This means that the individual results of the studies differed to some extent, for example, depending on the region or social factors such as education and income.
Meat-Free Diet and Development of Depression — These Factors Could Play a Role
The results suggest that a meat-free diet could be advantageously linked to mental health. Possible reasons:
- an overall healthier diet
- a healthier lifestyle
- more positive social factors, such as a higher level of education, employment, or a life partner
The less clear results for the flexitarian diet suggest that other influences — such as personal motivation, cultural factors, or social support — could also play a role. For example, people who only eat meat occasionally may have different motivations (e.g., diets or health conditions) than committed vegetarians or vegans.
Classification of the Study and Possible Limitations
The study’s focus on long-term research and meticulous analysis of social influences lend it a high degree of informativeness. Nevertheless, there are some limitations that should be taken into account when evaluating the results:
- The definitions of “meat-free” and “flexitarian” varied between the included studies and were not always consistent.
- Many of the studies examined recorded depression via self-reports or questionnaires, while medical diagnoses were less frequently documented.
- The reasons for abstaining from meat (e.g., ethical, health, or cultural motives) were not systematically recorded, although they could influence the relationship.
- Vegetarian and vegan diets were grouped together under the generic term “meat-free.” A distinction would have been useful here. The researchers themselves point out that vegans take dietary supplements such as vitamin B12 or omega-3 fatty acids more frequently. These could reduce the risk of depression. Whether the observed protective effect is, therefore, partly due to such additional measures could not be conclusively clarified with the available data.
Another important point is that the researchers also checked whether their results were possibly distorted by the fact that studies with positive or conspicuous results were preferentially published — a phenomenon known as “publication bias.” However, they found no evidence of this using standard test methods. This suggests that the results of the analysis are reliable overall.
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Conclusion on the Link Between a Meat-Free Diet and Depression
A meat-free diet appears to be associated with a lower likelihood of developing depression, while merely reducing meat intake shows no clear effect. However, the exact mechanisms behind this link remain unclear.
It is particularly clear: Psychosocial factors such as income, education, or social networks may influence the relationship between diet and depression more than previously thought. Further research is needed to identify these factors more precisely and to clarify the role played by motivation to change one’s diet.
Regrettably, Research Is all Too Frequently Marred by Bias
“The question of whether and to what extent animal products should be part of the diet is regularly part of controversial discussions. And the boundaries between personal preferences, ethics, cultural backgrounds, and health advantages and disadvantages are often blurred. Unfortunately, there is also far too often a bias on the part of scientists in research. This ‘bias’ can directly influence the studies themselves or affect the likelihood of their publication. The Spanish researchers have tried to take this problem into account. They also only looked at high-quality long-term studies. The outcome indicates that individuals following a meat-free diet have a reduced likelihood of developing depression. Nonetheless, the underlying factors remain unclear.
However, there is some evidence to suggest that a meat-free diet is associated with more beneficial psychosocial factors and possibly a healthier lifestyle overall.
I would classify my diet as somewhere between omnivorous and flexitarian. For me, this includes animal products as well as a lot of plant-based food. I consider dogmatic debates — those staunchly for or against a particular view — to be of limited value in health-related matters. Does this imply I’m not supportive of animal welfare? Certainly not! When it comes to meat, I mainly opt for organic products. It is pricier, yet I consume it less frequently as a result. But I also like plant-based products and sources of protein such as tofu, tempeh, pulses, etc. Unfortunately, these are also underestimated far too often.”