Is there an association being plant-based diets and mental health?

By Pooja Toshniwal PahariaJun 2 2023Reviewed by Lily Ramsey, LLM

In a recent study published in PLOS ONE, researchers determined the relationship between plant-origin diet indices (PDIs) and mental health disorders such as anxiety and depression among Iranian adults.

Study: The relationship between a plant-based diet and mental health: Evidence from a cross-sectional multicentric community trial (LIPOKAP) study. Image Credit: marilynbarbone/Shutterstock.com

Background

Mental health disorders, such as anxiety and depression, are major population health concerns globally due to their widespread prevalence and limited improvements.

Psychiatric disorders negatively impact an individual's health, life quality, survival, and eating habits. Recent research has demonstrated that nutrition has a significant impact on psychological well-being.

Plant-origin diets may confer neuroprotective benefits, and studies have found a link between PDI and anxiety and depression. However, data on the relationship between PDIs and mental well-being measures are limited.

Moreover, most studies included small sample sizes and specific populations (such as diabetics), limiting the generalizability of the findings.

About the study

In the present study, researchers evaluated the impact of plant-based diets on psychological well-being, using PDIs such as unhealthy PDI (uPDI) and healthy PDI (hPDI) among Iranians.

The Knowledge and Practice of Dyslipidemia Prevention, Management, and Control (LIPOKAP) study was conducted in community settings. Adults were recruited across five cities, i.e., Birjand, Isfahan, Kermanshah, Shahrekord, and Bandar Abas, from February 2018 to July 2019.

The present study used baseline data from the LIPOKAP trial as a cross-sectional analysis.

Food frequency questionnaires were used to assess dietary intake, and the Hospital Anxiety and Depression Scale (HADS) was used to evaluate mental health. Plant-based diet index versions used for the analysis included hPDI, uPDI, and an overall PDI.

Demographic data such as age, gender, socioeconomic status, gender, and smoking status were analyzed using self-reported questionnaires. Physical exercise was assessed using the International Physical Activity Questionnaire (IPAQ).

Multivariate logistic regression modeling was performed to calculate the odds ratios (ORs) after adjusting for covariates such as age, gender, energy, exercise, smoking habits, and marital status.

Individuals with a history of dyslipidemia-associated diseases, chronic renal disease, hepatic disease, immunological disorders, systemic diseases, and overestimation or underestimation of caloric intake (above 4,200.0 or below 800.0 or kcal per day, respectively) were excluded from the analysis.

Results and discussion

Initially, 2,456 adults were recruited, of whom 2,033 were eligible for the study. Participants with higher uPDI and PDI scores were younger than those with lower uPDI and PDI scores. Participants in the fourth PDI quartile were more likely to be current smokers.

Higher hPDI scores were related to lower caloric intake and greater healthy fruits, vegetables, legumes, and whole grains consumption.

Higher uPDI scores were associated with higher consumption of sweet drinks, desserts, and refined grains. PDI and hPDI were not related to anxiety and depression after covariate adjustment; however, the unadjusted data indicated that the highest uPDI intake increased depression risk by nearly two-fold (OR 2.1) and anxiety risk by and increased the risk of anxiety by 50.0% (OR 1.6).

Adjusting for covariates marginally altered the relationships (ORs for depression and anxiety in the fourth quartile were 2.0 and 1.5, respectively).

Anxiety affects food preferences adversely and increases the intake of unhealthy food items limiting fruit and vegetable consumption. Most unhealthy foods have a high glycemic load (GL), glycemic index (GI), and lower quantities of nutrients critical for mental fitness.

In addition, unhealthy foods may negatively impact the gut microbiome, alter mood, increase inflammation, and disrupt neuroplasticity and neurogenesis. Moreover, the functions of neurotransmitters such as serotonin and dopamine may be changed, leading to psychological distress.

Unhealthy foods are low in protein, and protein intake is reportedly negatively associated with depression, likely due to the effects of tryptophan on cognition and mood. The lack of significant associations between healthy PDI and anxiety and depression may be due to dietary uniformity.

Conclusions

The study findings showed that higher uPDI scores correlated with increased anxiety and depression risks, whereas PDI and hPDI did not show such associations, following previous studies.

The study findings provide valuable insights into beneficial health approaches to reduce the burden of diseases globally and indicate increasing the consumption of plant-based foods.

However, causal inferences could not be drawn due to the type of study design, and analysis was performed using self-reported data. Further research must assess probable confounding by food choices and diet types and include objective data evaluation.