New research published in journal psychological science The association between eating meat and experiencing depression was very weak, suggesting that there is likely no causal relationship. After analyzing data from tens of thousands of people over several years, scientists found that avoiding meat does not appear to be a significant risk factor for developing depression. This provides evidence that people who choose a vegetarian or vegan diet do not need to worry that their dietary choices will directly cause poor mental health.
In recent years, there has been increased public interest in the potential impact of plant-based diets on mental health. Researcher Christopher Hopwood said: “Some studies suggest a link between avoiding animal foods and depression, and some social media influencers have recommended eating meat to avoid depression.” “Previous studies have not been able to estimate population-level effects or examine causal assumptions as in this study.”
Many of our previous projects asked people to identify themselves as vegetarians, vegans, or omnivores. This classification approach may be flawed because the dietary labels chosen by individuals do not always correspond to their actual dietary behavior. To address this, the current study treated meat consumption as a continuous behavior and precisely measured how often people eat animal products.
Past projects also often relied on small, unrepresentative groups of people, making it difficult to apply their results to a broader population. Scientists found that previous research often ignored other lifestyle factors that influence mental health, such as age, income, education, and gender. The researchers designed this project to see if the association between meat consumption and depression is actually driven by these external demographic variables.
To get a more precise understanding, scientists analyzed existing data from three large ongoing national studies. These included panels from the Netherlands, Germany and Australia. This study included a highly representative sample of a total of 77,678 participants.
Participants regularly completed questionnaires detailing how often they ate meat, fish, and poultry. Frequency options ranged from not eating meat at all to consuming it every day or multiple times a day. Participants also answered standard questions about their mental health, specifically indicating how often they felt sad, hopeless, or lacking in energy over the past four weeks.
Using these repeated measurements, scientists were able to track changes in both diet and mood for specific individuals over time. The researchers controlled for age, gender, income, and education in their statistical analyses. This adjustment helps isolate the specific relationship between diet and mood by removing the influence of demographic factors known to influence both diet and mood.
Scientists found a very weak negative correlation between meat consumption and depression. The statistical association is so small that it is unlikely to have a noticeable effect on a person’s daily life. “The general pattern is that eating meat basically has no effect on depression one way or the other,” Hopwood says.
The researchers tested for so-called lag effects when looking at longitudinal data. They wanted to see if people who ate less meat than their personal average at one point predicted higher depression scores at the next survey assessment. They found no significant delay effects. This meant that a decrease in meat intake did not predict an increase in depressive symptoms in subsequent years.
The researchers also looked at whether experiencing depression led to later changes in eating habits. They also found no evidence of this reverse effect. Additionally, we tested whether living in a rural versus urban environment modifies the relationship between meat consumption and depression and found no contextual differences.
The scientists also investigated nonlinear patterns to see whether extreme meat eating was associated with poor mood. “Depression increased sharply when meat intake was very high, suggesting that eating too much meat may be associated with depression,” Hopwood said. Still, the overall data shows that people who eat average amounts of meat have the lowest levels of depression.
While these findings are detailed, the study relied solely on self-reported data, requiring participants to accurately remember and report their eating habits and emotions. “While we were unable to directly test for causality, our results strongly suggest that a causal relationship is unlikely,” Hopwood said. “Also, we only tested people from three Western countries, so results may be different in other cultures.”
Age and living environment can also have a profound effect on mental health and diet. “There are certain developmental and life stages (such as during pregnancy and after exposure to animal husbandry) where nutritional needs change, and our results do not address these issues in detail,” Hopwood explained. Future studies may benefit from using more frequent assessments to track rapid changes in mood and eating behavior.
In the future, the researchers hope to investigate how diet affects certain mental health conditions. “While we believe the results of this study are conclusive regarding meat consumption and depression in the general population, there may be certain subgroups that may be relevant, such as people who have been diagnosed with eating disorders or who have significant concerns about the environment or animal rights,” Hopwood said. “We’re interested in studying those subgroups.”
Researchers want to provide reliable information about public health and wellness. “We believe it’s important that people make dietary decisions based on evidence, and we’re concerned about people making decisions that could harm themselves, the environment and animals based on uninformed opinions shared on social media,” Hopwood added. “We hope these results will provide evidence to make appropriate dietary decisions for such people.”
“The association between meat eating and depression is small and a causal relationship is unlikely,” the study was authored by Nicholas Poe-Gee Tan, Michael D. Kramer, Peter Haner, Wiebke Brydorn, and Christopher J. Hopwood.
