Mental health is essential to our overall well-being. Mental health encompasses our emotional, psychological, and social well-being. It impacts the way we think, feel, handle stress, and make decisions. Many studies have shown the benefits of vegetarianism on our physical health, such as prevention of cardiovascular disease, diabetes, and cancer, but what does the research say about vegetarianism on our mental health?

In this article we explain (in plain English!) the conclusions of scientific studies that have looked at vegetarian mental health. 

Vegetarian diets consist of plant-based foods rich in whole grains, legumes, nuts, seeds, fruits, and vegetables, while avoiding red meat, processed meat products, refined foods, and sweets.

There are several variations of a vegetarian diet:

  • Lacto-vegetarians allow the consumption of low-fat dairy products
  • Ovo-vegetarians allow the consumption of eggs
  • Pescatarians allow the consumption of fish
  • Pollotarians allow lean white meat such as chicken to be consumed.

Benefits of Vegetarianism on Mental Health

In the sections that follow we highlight studies that have linked vegetarianism with improved mood, reduced psychological disorders (anxiety and depression), improved sleep quality, cognitive function, and look at the mechanism of how plant-based foods act on our mental health.

Improved Mood

A vegetarian diet may have a positive impact on your mood. Researchers from Cornell University conducted a “Nutritional and Mood assessment of a 30-day vegan diet” on non-vegetarians. Participants reported a significant change in mood, with greater physical strength, enthusiasm and energy when switching to a vegan diet (Olabi et al., 2015).

A study conducted by Beezhold & Johnston (2012) reported that omnivores who restricted meat, fish and poultry and followed a vegetarian diet for two weeks showed an increase in mood scores using the Profile of Mood States questionnaire and the Depression Anxiety and Stress Scales.

Another study published in the journal Nutritional Neuroscience reported that “a strict plant-based diet does not appear to negatively impact mood; a reduction of animal food intake may have mood benefits” (Beezhold et al., 2014).

According to Głąbska et al. (2020), adding more fruits and vegetables to your diet can enhance your mental health “any increase in the consumption of fruits and vegetables results in the improvement of well-being, enhances happiness, and decreases depressive symptoms”.

These studies support the fact that a vegetarian diet may have a beneficial impact on improving your mood.

Decreased Risk of Psychological Disorders (Anxiety & Depression)

Several academic papers have shown the positive benefits of following a plant-based diet high in whole grains, fruits, vegetables, legumes, and nuts on psychological disorders such as anxiety and depression.

A study published in the European Journal of Clinical Nutrition, investigated the link between depressive symptoms and dietary habits of mid-aged women in 2001 and 2004, those who adhered to a Mediterranean diet exhibited a lower frequency of depressive symptoms “Consumption of a ‘Mediterranean-style’ dietary pattern by mid-aged women may have a protective influence against the onset of depressive symptoms” (Rienks et al., 2012).

Substituting a Mediterranean-style diet with fish oil may improve depression. Scientists at the University of South Australia found that participants who suffered from depression and changed to a Mediterranean diet supplemented with fish oil for three months reported a higher reduction in depression and enhanced mental health scores (Parletta et al., 2019).

A paper published in the journal of Clinical Nutrition, looked at the effect of a healthful plant-based diet and unhealthful plant-based diet on anxiety, depression, psychological distress, and obesity in Iranian women. They reported that women who followed a healthy plant-based diet were less likely to suffer from anxiety and depression, compared to women who followed an unhealthful plant-based diet. Those following an unhealthful plant-based diet were also more likely to be obese “A plant-based diet, particularly healthful-rich plant foods were inversely associated with psychological disorders” (Zamani et al., 2020).

A plant-based diet coupled with exercise may be beneficial in treating individuals who suffer from moderate to severe depression and anxiety “an intervention of diet, exercise, lifestyle and behaviour modification may provide considerable benefits for moderate to severe depression and anxiety” (Null & Pennesi, 2017).

A study exploring the relationship between a vegetarian diet and depression among South Asians living in the United States found that participants following a vegetarian diet were less likely to suffer from depression “43% lower odds of depression among vegetarians” (Jin et al., 2021).

This is further supported by Daneshzad et al. (2019) who stated “higher adherence to a healthful plant-based diet is associated with lower odds of mental disorders” and Lai et al. (2013) who reported “high intakes of fruit, vegetables, fish, and whole grains may be associated with a reduced depression risk”.

This evidence clearly shows the positive impact a vegetarian diet can have on anxiety, depression and psychological distress.

Cognitive Function and Alzheimer’s disease

Healthful plant-based foods play a role in healthy brain ageing. Westernized diets which are high in inflammatory causing compounds may lead to an increased risk of dementia, caused by Alzheimer’s disease (AD). Alzheimer’s disease is the most common neurodegenerative disease in the world.

Fruits, vegetables and seafood have protective effects on brain health “Among specific foods with evidence of neuroprotection are green leafy vegetables, other vegetables, berries, and seafood” While high saturated fat diets associated with animal products have a negative impact on cognitive health “Diets high in saturated and trans fats have been shown to increase cognitive decline and the risk of developing dementia” (Morris, 2016).

According to Gregorevic (2022) a vegetarian diet is the best way to protect your brain from degeneration “the key is eating a large variety of plant-based foods and ensuring that the diet contains all necessary micronutrients”.

Improved Sleep Quality

A good night’s sleep is essential for our bodies to recover from the day’s stresses, it is also important for our brains. Lack of quality sleep and insomnia may lead to irritability and psychological disorders. Poor sleep duration and quality could also lead to an increased risk of cardiovascular disease (Javaheri & Redline, 2012).

Plant-based diets may have a positive impact on our sleep. A paper published in the journal Sleep, reported that participants who followed a Mediterranean diet were more likely to have a good night’s sleep “Mediterranean-style diet is associated with adequate sleep duration, less insomnia symptoms, and less likely to have insomnia accompanied by short sleep” (Castro-Diehl et al., 2018).

This evidence is backed-up by Mamalaki et al. (2018) who reported that participants who followed a Mediterranean diet had a better quality sleep “sleep quality is associated with Mediterranean diet adherence”.

Researchers at Cambridge University investigated the link between a plant-based diet and sleep and mental health status in diabetic women “patients who adhered to animal-based diets rather than plant-based diets were more likely to be poor sleepers and have mental health disorders” (Daneshzad et al., 2019).

Mechanism of Plant-Based Diet on Mental Health

This section looks at the mechanism at which plant-based foods affect our mental health.

Inflammation and Oxidative Stress

Plant-based diet plays an essential role on mental health by preventing inflammation and oxidative stress.

Inflammation and oxidative stress are thought to cause changes to the healthy functioning of the brain leading to a negative impact on mental health “Oxidative damage in the brain causes nervous system impairment; oxidative stress has also been implicated in depression, anxiety disorders and high anxiety levels” (Black et al., 2019; Bouayed et al., 2009).  

High levels of inflammation is thought to activate feelings of sadness “Inflammation can trigger melancholic symptoms through activation of inflammatory pathways in the brain” (Slavich & Irwin, 2014).

Anti-oxidant and Anti-inflammatory Effect

Vegetarian diets rich in plant-based foods abundant in antioxidants and polyphenols are able to protect the body from inflammation and oxidative stress “Vegetarian diets are inherently rich in antioxidants, and adherence to vegetarian diets is associated with low oxidative stress” (Johnston, 2017).

Polyphenols are a natural compound found in food sources such as berries, nuts, coffee and tea “polyphenols affect a broad range of mechanisms in the brain that can assist in the maintenance of cognitive and mental health, as well as the recovery from neurodegenerative diseases” (Gomez-Pinilla & Nguyen, 2012).

Folate and magnesium, nutrients that are abundant in plant food sources, aid in the production of neurotransmitters such as serotonin and dopamine (‘happy hormones’). Magnesium has strong anti-inflammatory effects - low levels of magnesium in the body may cause the on-set of depression (Rao et al., 2008).

Gut-Brain Axis

Recently, we are learning more about the important role our gut microbes play on our mental health “There is now over-whelming evidence to support the fact that gut microbes have a major impact on central neurochemistry and behaviour, especially stress-related disorders such as depression” (Dinan et al., 2019).

A healthy microbiome (The trillions of bacteria and yeasts that live in our gut) is essential for proper brain function and mental health (Foster & Neufeld, 2013). Stress and high-fat diets may affect the healthy balance in your gut and may lead to psychological disorders such as anxiety and depression, and illness.  

Diet influences the gut microbiome. Plant foods such as onion, chicory, garlic, banana, and asparagus act as prebiotics (foods containing fructo-oligosaccarides that help the good gut microbes grow) and may alleviate anxiety and depression. (Sabater-Molina et al., 2009; Taylor & Holscher, 2020).

Polyphenols, which are abundant in vegetarian diets rich in fruits, vegetables, coffee and tea are beneficial in controlling the composition of the gut microbiome.

Plant-based foods provide healthy nutritious fuel for our ‘good’ gut microbes to grow and thrive, and prevent harmful pathogenic bacteria from surviving which could cause an in balance leading to inflammation and in turn affecting our mental health.

Possible Drawbacks of Vegetarianism on Mental Health

A few papers have suggested that vegetarian diets do not have an impact on mental health.

A research paper published in the Journal of Affective Disorders found no link between a vegetarian diet and mental health in US, Russian and German individuals, however a small rise in anxiety and depression among Chinese students was reported “Vegetarianism is not associated with mental health in the US, Russia, or Germany, but is associated with anxiety and depression in China” (Lavallee et al., 2019).

A paper published in Nutrition Reviews found that vegetarian diets lead to an increase in depression, while anxiety decreased, mainly among individuals younger than 26 years “Vegan or vegetarian diets were related to a higher risk of depression and lower anxiety scores” (Iguacel et al., 2021).

It has been suggested that the reason for these conflicting studies could be due to the fact that participants who reported following a vegetarian diet may not have been following a balanced, healthful plant-based diet, but a plant-based diet consisting largely of refined grains, sweets, potatoes, fruit juices, and sweetened beverages.

Wrapping Up

A healthful-rich plant-based diet is essential for optimal mental health; it is linked to reduced rates of depression, provides a beneficial effect on our gut microbiome, and studies suggest that certain plant foods have an anti-depressant effect on our brains (Dinan et al., 2019).


A well-planned, balanced, nutritious vegetarian diet that is rich in healthful plant-based foods full of fiber and antioxidants, and low in red and processed meats, and refined sugars can provide your body with the defences it needs to keep depression at bay and ensure your body and mind stay happy and healthy for a long time.

References:

  • Beezhold, B. L., & Johnston, C. S. (2012). Restriction of meat, fish, and poultry in omnivores improves mood: a pilot randomized controlled trial. Nutrition journal, 11(1), 1-5.
  • Beezhold, B., Radnitz, C., Rinne, A., & DiMatteo, J. (2015). Vegans report less stress and anxiety than omnivores. Nutritional neuroscience, 18(7), 289-296.
  • Black, C. N., Bot, M., Scheffer, P. G., Cuijpers, P., & Penninx, B. W. (2015). Is depression associated with increased oxidative stress? A systematic review and meta-analysis. Psychoneuroendocrinology, 51, 164-175.
  • Bouayed, J., Rammal, H., & Soulimani, R. (2009). Oxidative stress and anxiety: relationship and cellular pathways. Oxidative medicine and cellular longevity, 2(2), 63-67.
  • Bremner, J. D., Moazzami, K., Wittbrodt, M. T., Nye, J. A., Lima, B. B., Gillespie, C. F., ... & Vaccarino, V. (2020). Diet, stress and mental health. Nutrients, 12(8), 2428.
  • Castro-Diehl, C., Wood, A. C., Redline, S., Reid, M., Johnson, D. A., Maras, J. E., ... & St-Onge, M. P. (2018). Mediterranean diet pattern and sleep duration and insomnia symptoms in the Multi-Ethnic Study of Atherosclerosis. Sleep, 41(11), zsy158.
  • Dinan, T. G., Stanton, C., Long-Smith, C., Kennedy, P., Cryan, J. F., Cowan, C. S., ... & Sanz, Y. (2019). Feeding melancholic microbes: MyNewGut recommendations on diet and mood. Clinical Nutrition, 38(5), 1995-2001.
  • Foster, J. A., & Neufeld, K. A. M. (2013). Gut–brain axis: how the microbiome influences anxiety and depression. Trends in neurosciences, 36(5), 305-312.
  • Głąbska, D., Guzek, D., Groele, B., & Gutkowska, K. (2020). Fruit and vegetable intake and mental health in adults: a systematic review. Nutrients, 12(1), 115.
  • Gomez-Pinilla, F., & Nguyen, T. T. (2012). Natural mood foods: the actions of polyphenols against psychiatric and cognitive disorders. Nutritional neuroscience, 15(3), 127-133.
  • Gregorevic, K. (2022). Diet in the Prevention of Dementia. Psychiatric Annals, 52(2), 67-71.
  • Iguacel, I., Huybrechts, I., Moreno, L. A., & Michels, N. (2021). Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis. Nutrition reviews, 79(4), 361-381.
  • Javaheri, S., & Redline, S. (2012). Sleep, slow-wave sleep, and blood pressure. Current hypertension reports, 14(5), 442-448.
  • Jin, Y., Kandula, N. R., Kanaya, A. M., & Talegawkar, S. A. (2021). Vegetarian diet is inversely associated with prevalence of depression in middle-older aged South Asians in the United States. Ethnicity & health, 26(4), 504-511.
  • Johnston, C. S. (2017). Vegetarian Diet and Possible Mechanisms for Impact on Mood. In Vegetarian and Plant-Based Diets in Health and Disease Prevention (pp. 493-509). Academic Press.
  • Lavallee, K., Zhang, X. C., Michalak, J., Schneider, S., & Margraf, J. (2019). Vegetarian diet and mental health: Cross-sectional and longitudinal analyses in culturally diverse samples. Journal of affective disorders, 248, 147-154.
  • Mamalaki, E., Anastasiou, C. A., Ntanasi, E., Tsapanou, A., Kosmidis, M. H., Dardiotis, E., ... & Yannakoulia, M. (2018). Associations between the mediterranean diet and sleep in older adults: Results from the hellenic longitudinal investigation of aging and diet study. Geriatrics & gerontology international, 18(11), 1543-1548.
  • Morris, M. C. (2016). Nutrition and risk of dementia: overview and methodological issues. Annals of the New York Academy of Sciences, 1367(1), 31-37.
  • Null, G., & Pennesi, L. (2017). Diet and lifestyle intervention on chronic moderate to severe depression and anxiety and other chronic conditions. Complementary therapies in clinical practice, 29, 189-193.
  • Olabi, A., Levitsky, D. A., Hunter, J. B., Spies, R., Rovers, A. P., & Abdouni, L. (2015). Food and mood: A nutritional and mood assessment of a 30-day vegan space diet. Food Quality and Preference, 40, 110-115.
  • Parletta, N., Zarnowiecki, D., Cho, J., Wilson, A., Bogomolova, S., Villani, A., ... & O’Dea, K. (2019). A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional neuroscience, 22(7), 474-487.
  • Rao, T. S., Asha, M. R., Ramesh, B. N., & Rao, K. J. (2008). Understanding nutrition, depression and mental illnesses. Indian journal of psychiatry, 50(2), 77.
  • Rienks, J., Dobson, A. J., & Mishra, G. D. (2013). Mediterranean dietary pattern and prevalence and incidence of depressive symptoms in mid-aged women: results from a large community-based prospective study. European journal of clinical nutrition, 67(1), 75-82.
  • Sabater-Molina, M., Larqué, E., Torrella, F., & Zamora, S. (2009). Dietary fructooligosaccharides and potential benefits on health. Journal of physiology and biochemistry, 65(3), 315-328.
  • Slavich, G. M., & Irwin, M. R. (2014). From stress to inflammation and major depressive disorder: a social signal transduction theory of depression. Psychological bulletin, 140(3), 774.
  • Taylor, A. M., & Holscher, H. D. (2020). A review of dietary and microbial connections to depression, anxiety, and stress. Nutritional neuroscience, 23(3), 237-250.
  • Zamani, B., Daneshzad, E., Siassi, F., Guilani, B., Bellissimo, N., & Azadbakht, L. (2020). Association of plant-based dietary patterns with psychological profile and obesity in Iranian women. Clinical Nutrition, 39(6), 1799-1808.

Mental Health Benefits Studies

Mental Health Benefits of Vegetarianism

Date

Name of Paper

Journal Name

Link to Paper

2021

Fruit and Vegetable Dietary Patterns and Mental Health in Women: A Systematic Review

Nutrition Reviews

2021

The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework

PloS one

2021

Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis

Nutrition Reviews

2020

Vegetarian or Vegan Diet: Stimulating or at Risk to Mental Health?

Book

2020

Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis

Nutrition Reviews

2020

Diet, Stress and Mental Health

Nutrients

2019

Association of plant-based dietary patterns with psychological profile and obesity in Iranian women

Clinical Nutrition

2019

Feeding melancholic microbes: MyNewGut recommendations on diet and mood

Clinical Nutrition

2019

Vegetarian diet is inversely associated with prevalence of depression in middle-older aged South Asians in the United States

Ethnicity and Health

2019

Vegetarian diet and mental health: Cross-sectional and longitudinal analyses in culturally diverse samples

Journal of Affective Disorders

2019

Adherence to Mediterranean dietary pattern is inversely associated with depression, anxiety and psychological distress

Nutritional Neuroscience

2019

Fruit and Vegetable Intake and Mental Health in Adults: A Systematic Review

Nutrients

2019

Association Between Fruit/Vegetable Consumption and Mental-Health-Related Quality of Life, Major Depression, and Generalized Anxiety Disorder: A Longitudinal Study in Thailand

Iranian Journal of Psychiatry and Behavioural Science

2019

Association of dietary acid load and plant-based diet index with sleep, stress, anxiety and depression in diabetic women

British Journal of Nutrition

2018

Antidepressant foods: An evidence-based nutrient profiling system for depression

World Journal of Psychiatry

2017

Diet and lifestyle intervention on chronic moderate to severe depression and anxiety and other chronic conditions

Complementary Therapies in Clinical Practice

2017

A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED)

Nutritional Neuroscience

2017

28 - Vegetarian Diet and Possible Mechanisms for Impact on Mood

Book: Vegetarian and Plant-Based Diets in Health and Disease Prevention

2015

A Multicenter Randomized Controlled Trial of a Nutrition Intervention Program in a Multiethnic Adult Population in the Corporate Setting Reduces Depression and Anxiety and Improves Quality of Life: The GEICO Study

American Journal of Health Promotion

2015

Food and mood: A nutritional and mood assessment of a 30-day vegan space diet

Food Quality and Preference

2014

Vegans report less stress and anxiety than omnivores

Nutritional Neuroscience

2014

A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults

The American Journal of Clinical Nutrition

2013

Mediterranean dietary pattern and prevalence and incidence of depressive symptoms in mid-aged women: results from a large community-based prospective study

European Journal of Clinical Nutrition

2013

Intake of Mediterranean foods associated with positive affect and low negative affect

Journal of Psychosomatic Research

2013

Maternal and Early Postnatal Nutrition and Mental Health of Offspring by Age 5 Years: A Prospective Cohort Study

Journal of the American Academy of Child & Adolescent Psychiatry

2013

Natural mood foods: The actions of polyphenols against psychiatric and cognitive disorders

Nutritional Neuroscience

2012

Restriction of meat, fish, and poultry in omnivores improves mood: A pilot randomized controlled trial

Nutrition Journal

2012

Vegetarian diet in type 2 diabetes – improvement in quality of life, mood and eating behaviour

Diabetic Medicine

2010

Vegetarian diets are associated with healthy mood states: a cross-sectional study in Seventh Day Adventist adults

Nutrition Journal

2009

Association of the Mediterranean Dietary Pattern With the Incidence of Depression

The Seguimiento Universidad de Navarra/University of Navarra Follow-up (SUN) Cohort

Arch Gen Psychiatry

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