ISNPR member Megan Lee won the ISNPR Outstanding Publication award for round 1 2025 for their study ‘The Certainty of the Evidence on Plant- vs Meat-Predominant Dietary Patterns and Depression: An Umbrella Review’, published in Nutrition Reviews

Megan shares some details about their study.

Plant vs. Meat Based Diets and Mental Health: What Does the Evidence Really Say?

Depression impacts millions of people worldwide and is a leading cause of disability, making the search for effective prevention and treatment strategies more important than ever. Among the many lifestyle factors being explored, diet has emerged as a promising area for supporting mental health. But when it comes to plant-based versus meat-based diets, the evidence is far from clear-cut.

A recent umbrella review published in Nutrition Reviews by Lee and colleagues sought to clarify the relationship between plant- and meat-predominant dietary patterns and depression. The review analysed nine systematic reviews and meta-analyses, each examining how vegan, vegetarian, omnivorous, and carnivorous diets relate to depressive symptoms. The findings are mixed: some studies suggested that diets rich in plant foods may reduce the risk of depression, while others reported that people following vegan or vegetarian diets experience increased risk of depressive symptoms than those who include meat in their diets.

Why such conflicting results? The review highlights several important factors. First, much of the research is based on observational studies, which can’t prove cause and effect. Second, there’s a lot of variation in how diets and depression are measured across studies, making it hard to compare results. Third, the quality and composition of plant-based diets matter-some people might miss out on key nutrients like B vitamins, iron, zinc, and omega-3 fatty acids if their diets aren’t well planned. Finally, there’s a lot of overlap in the primary studies included in different reviews, which can make it seem like there’s more evidence than there really is.

The review also points out that high-quality diets-such as the Mediterranean diet, which is rich in vegetables, fruits, nuts, and whole grains-are consistently linked to better mental health, regardless of whether they include meat. This suggests that the overall quality and variety of the diet may be more important than simply avoiding or including animal products.

While there’s growing interest in the role of diet in mental health, the evidence on plant- versus meat-predominant diets and depression remains uncertain. More primary research is needed.