Globally, more than 350 million people experience depressive symptoms, making it essential to explore diet as a potential contributing factor. While plant-forward diets are often associated with better mental health, data also shows that vegans and vegetarians tend to report higher depressive symptoms compared to omnivores. This apparent contradiction is what prompted us to take a closer look at diet quality rather than diet type.
Our study revealed that higher diet quality was associated with fewer depressive symptoms, regardless of whether participants followed a plant-based or omnivorous diet. Interestingly, there was no significant difference in depressive symptoms between high-quality diets of either type. To ensure accuracy, we controlled for significant lifestyle factors such as alcohol consumption, smoking, BMI, marital status, and co-morbid anxiety. While the effect sizes were relatively small and may not yet be clinically significant, the results suggest that improving diet quality is a promising strategy for enhancing mental well-being.
Dr Megan Lee, an Assistant Professor at Bond University, friend of The Proof, and the study’s lead author, explains that high-quality diets—whether omnivorous or plant-based—share common features. They include fresh fruits, vegetables, whole grains, nuts, seeds, legumes, herbs, spices, and water. On the other hand, lower-quality diets, regardless of type, are characterized by high consumption of ultra-processed, refined, and sugary foods. Dr Lee notes that when individuals adopt specific diets such as vegan, vegetarian, or keto, they often reduce their intake of ultra-processed foods, which might be the key driver behind improvements in physical and mental health.
This study builds on Dr Lee’s extensive research portfolio, which includes work on health promotion, lifestyle medicine, postpartum body image, and eating patterns. Her research consistently seeks to bridge the gap between science and application, empowering individuals to make evidence-based choices that support both their physical and mental well-being.
While the study sheds light on the role of diet quality, the question still remains: Why do vegans and vegetarians still report higher rates of depressive symptoms? Dr Lee believes the answer may lie beyond diet and is currently conducting interviews and focus groups to uncover potential factors. She is also optimistic about future research in this field, particularly studies examining the gut-brain connection. The Food Mood Centre at Deakin University is leading exciting research on how plant-based foods and the gut microbiome influence mental health, which could transform the field of nutritional psychiatry.
Based on the study’s findings, Dr Lee offers practical advice for optimising mental health through diet.
- Focus on Gut Health: Incorporate 30+ varieties of plants each week. These provide essential fiber, antioxidants, and polyphenols to nourish the gut and brain.
- Eat the Rainbow: Choose a wide range of colourful fruits and vegetables for diverse nutrients.
- For Omnivores, Adopt a Mediterranean Approach: Emphasise plant-based foods like beans and legumes, with moderate amounts of oily fish and dark chocolate. Use meat sparingly, as a seasoning rather than the main component.
- Stay Informed: Lean into resources like The Proof podcast (Shameless mention, thanks Dr Lee) for expert insights, and follow gut health leaders like Tim Spector and Dr Will Bulsiewicz for the latest in microbiome science.
To hear more from Dr Lee, check out her episode on The Proof. We explored the link between diet and mental health, covering everything from dietary science to media misinterpretations. It was a great discussion that you won’t want to miss.
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