A recent study published in Nutritional Neuroscience has shed light on the potential connection between diet quality and mental health. The study found that individuals with high adherence to a Mediterranean diet had altered brain chemistry and structure compared to those with low adherence, hinting at beneficial changes.
The researchers aimed to address a significant gap in understanding how diet influences mental health. While preclinical studies have established a link between dietary patterns and brain chemistry, these findings need to be confirmed in human studies.
Common mental disorders affect millions worldwide and pose substantial social, economic, and health burdens. Symptoms such as low mood, worry, and rumination exacerbate these issues, making it crucial to explore non-pharmacological approaches, like diet, that could help manage these conditions. The researchers hypothesized that diet quality would be associated with levels of key neurotransmitters and brain structure, which in turn could influence mental health outcomes.
“The mechanisms of action associating diet with common mental disorders are largely identified in preclinical studies but need to be fully confirmed and elucidated in human studies. We wanted to fill this gap by conducting this research,” explained study author Piril Hepsomali, a lecturer in psychology at the University of Reading.
The researchers recruited 164 participants from the Universities of Roehampton and Royal Holloway, as well as the general public in London and surrounding areas. Participants were screened using the Mediterranean Diet Adherence Screener (MEDAS), a tool designed to assess adherence to the Mediterranean diet, which is known for its high quality and health benefits. Based on their MEDAS scores, 38 participants were selected and divided into two groups: those with high adherence to the Mediterranean diet (MEDAS score > 8) and those with low adherence (MEDAS score < 6).
All participants completed a series of questionnaires to assess demographic variables, dietary habits, and mental health symptoms. These included the MEDAS, the Depression, Anxiety, and Stress Scale (DASS), the Ruminative Response Scale (RRS), and the EPIC Norfolk Food Frequency Questionnaire (FFQ). These tools provided a comprehensive picture of each participant’s diet quality, mental health status, and habitual food intake.
The core of the study involved brain imaging. The researchers used a 3 Tesla Siemens Magnetom scanner to acquire structural MRI images and 1H-MRS to measure neurotransmitter levels in the medial prefrontal cortex (mPFC). This region of the brain is critical for affective disorders, making it a focal point for this study. The 1H-MRS technique allowed the researchers to quantify levels of gamma-aminobutyric acid (GABA) and glutamate, key neurotransmitters involved in brain excitability and inhibition.
The researchers found that participants with higher adherence to the Mediterranean diet showed higher levels of GABA and lower levels of glutamate in the mPFC compared to those with lower adherence. This finding is crucial because GABA is an inhibitory neurotransmitter that helps to reduce neuronal excitability, whereas glutamate is an excitatory neurotransmitter that, in excess, can lead to neuronal damage. The balance between these neurotransmitters is essential for maintaining mental health, and an imbalance is often implicated in conditions like anxiety and depression.
In terms of brain structure, Hepsomali and her colleagues found that individuals with higher diet quality had greater gray matter volume in the right precentral gyrus, a region involved in motor control and cognitive functions. This result is consistent with previous research suggesting that better diet quality is associated with larger brain volumes, particularly in regions important for cognitive and emotional regulation.
Interestingly, the researchers did not find direct associations between diet quality and measures of depression, anxiety, or stress. However, they did observe that higher rumination scores were linked to reduced gray matter volume in the right precentral gyrus and increased glutamate levels in the mPFC. Rumination, characterized by repetitive and persistent negative thinking, is a significant cognitive symptom in many mental health disorders.
The findings provide evidence that a person’s diet “might be associated with alterations in their brain chemistry and structure, and these alterations might contribute to how good or bad they feel,” Hepsomali told PsyPost.
However, he cautioned that “this is a preliminary study, with a small sample size, so our results would benefit from replication in a larger sample. Also, this is a cross-sectional study, we could not determine cause and effect relationships. In other words, we cannot say that unhealthy diets cause alterations in the brain. It may be the case that individuals with poor mental health status, choose poor quality diets, because of these neural alterations. So further longitudinal studies are needed.”
“We would like to replicate our preliminary findings in a bigger sample, ideally while utilizing other biomarkers and assess whether adherence to healthy and/or low GLU and/or high GABA diets and/or certain nutrients may alter brain chemistry and structure and improve common mental disorder symptoms,” Hepsomali added.
The study, “Adherence to unhealthy diets is associated with altered frontal gamma-aminobutyric acid and glutamate concentrations and grey matter volume: preliminary findings,” was authored by Piril Hepsomali, Adele Costabile, Marieke Schoemaker, Florencia Imakulata, and Paul Allen.
