Researchers from Queensland’s Bond University have found that a low-quality plant-based diet, compared to a diet rich in fresh produce, could lead to poorer mental health.
Nutritional psychiatry researcher Megan Lee said the finding was particularly significant given the increasing popularity of vegan and vegetarian lifestyles and the proliferation of packaged foods targeted at those groups.
Processed foods are high in refined vegetable oils, grains, salt and sugar.
“There is a general perception that following a plant-based diet is inherently healthy but like any diet it comes down to what you put in your mouth,” Lee said.
“Vegans and vegetarians are not automatically eating heaps of fruit and veg because there are all these products out there that are fully processed, fully refined.”
People may inadvertently be consuming high levels of processed plant foods which is a known risk factor for increased depression.
During the study, researchers looked at the diet and mental health of 219 vegans and vegetarians aged 18-44 across the country, who were then asked to complete relevant questionnaires.
Researchers found those with lots of fresh fruit, vegetables, nuts, seeds, legumes and whole grains in their diet were at a lower risk of depression compared to those on low-quality diets.
The link in diet and the risk of depression was likely due to the presence of complex carbohydrates, fibre, probiotics and antioxidants, which have all been found to decrease symptoms of depression, Lee said.
“It seems to have more a protective role,” she said.
“Our research did not find that a plant-based diet was a treatment or fix for those who were already depressed.”
Vegans and vegetarians are already more vulnerable to depression than the general population, Lee added.
“We think this (susceptibility to depression) might be because vegans and vegetarians tend to be more conscious about external issues—animal welfare, environmental concerns—and they can be ostracised socially because of their choice of diet,” she said.
The research also found meat-eaters can also protect their mental health by consuming more fruits and vegetables.