Food and Behaviour Research

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Plant-based dietary quality and depressive symptoms in Australian vegans and vegetarians: a cross-sectional study

Lee M, Eather R, Best T (2021) BMJ  DOI: 10.1136/bmjnph-2021-000332  

Web URL: Read this and related articles on BMJ


Plant-based dietary patterns (vegan and vegetarian) are often considered ‘healthy’ and have been associated with broad health benefits, including decreased risk of obesity and ill health (cardiovascular disease, blood glucose and type II diabetes). However, the association between plant-based diets and mood disorders such as depression remains largely equivocal.

This cross-sectional study of 219 adults aged 18–44 (M=31.22, SD=7.40) explored the associations between an estimate of overall plant-based diet quality and depression in vegans (n=165) and vegetarians (n=54).

Overall plant-based diet quality was associated with depressive symptoms in vegans and vegetarians F(1, 215)=13.71, p<0.001 accounting for 6% of the variation in depressive symptoms.

For those without depression, higher diet quality was protective against depressive symptoms F(1, 125)=6.49, p=0.012. Conversely, for those with depression no association with diet quality was found F(1, 89)=0.01, p=0.963.

These findings suggest that a high-quality plant-based diet may be protective against depressive symptoms in vegans and vegetarians. In line with emerging research between food and mental health, higher-quality dietary patterns are associated with a reduced risk of depressive symptoms.

Given the rapidly increasing rate of vegan and vegetarian food products within Australia, understanding the potential mechanisms of effects through which a plant-based diet may influence depressive symptoms is required.


This study found higher rates of depression in young vegan or vegetarian adults whose diets were of 'low quality' (i.e. high in ultra-processed foods) compared with those eating 'higher-quality' diets, based on whole or minimally processed foods.

An abundance of evidence already shows that any diet rich in ultra-processed foods is likely to be less beneficial for health - physical and mental - than a diet mainly consisting of fresh, whole or minimally processed foods, so this finding is not very surprising.

Vegetarian and vegan diets are extreme versions of a so-called 'plant-based' diet.  But that term does NOT mean vegan or vegetarian. It means a diet that is mainly based around plant-derived foods - as most traditional human diets were until the industrialisation of the food supply.  Classic and well-studied examples include the 'Mediterranean-type' diet, or the traditional Nordic diet - both of which include fish and seafood, as well as small quantities of meat and dairy products.

The distinction is important, because animal-derived foods provide many essential nutrients that can't be obtained easily, if at all, from plant foods - and most of them are particularly important for brain health.  Examples include omega-3 DHA, iodine, choline, Vitamin B12, iron and zinc, among others. 

For this reason, vegetaran or vegan diets are not necessarily 'healthy' - particularly for the brain - unless they are very well-planned and properly supplemented.

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