Depression due to special diets? Study gives new clues

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Of: Caroline Schaefer

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New research suggests that a proline-rich diet is associated with an increased risk of developing depression. (symbol photo) © Monkey Business 2/imago

Diets with a certain amino acid, found primarily in animal foods, are said to be more likely to trigger depression.

Barcelona – Depression is one of the most common illnesses, but also one of the most underestimated. The result of a 2016 study showed that 8.2 percent of German adults aged 18 to 79 develop unipolar or persistent depressive disorder within a year.

Mental illness cannot be attributed to a single trigger, but often arises from the interaction of different factors. New research now suggests that the amino acid called proline is linked to depression.

Write mood disorder
common symptoms inner emptiness, apathy, doubts, fears

Depression study: a diet rich in proline should increase the risk

Researchers from the Girona Biomedical Research Institute (IDIBGI) and Pompeu Fabra University (UPF) in Barcelona have studied the role of the amino acid in humans, mice and flies. Proline is a non-essential amino acid found in beef, pork, and chicken, gelatin, fish, and offal such as liver, eggs, and some types of cheese. The scientific journal Cell Metabolism published research showing that a diet high in proline is associated with an increased risk of developing depression.

depression diet? Study provides new details

For data collection, the type and amount of amino acids in the participants’ diet were analyzed on the one hand, and on the other hand the test subjects had to indicate their depressive mood through a questionnaire. “We were surprised that proline use was more strongly associated with depression,” said one of the lead researchers, José Manuel Fernández-Real of IDIBGI.

However, that didn’t mean that everyone who ate a lot of proline was automatically more depressed. According to the researchers, the intestinal microbiota (intestinal flora) is also decisive in relation to depression. “The microbiota of patients with high proline intake but low plasma proline levels resembled the microbiota associated with low levels of depression,” said study leader Jordi Mayneris-Perxachs.

Depression: does proline increase the risk? Experiments with mice provide information

To test whether the presence of proline is a cause or a consequence of depressed mood, several microorganisms from the participants were transplanted into mice. Mice that received participants’ high-proline microbiota were more prone to depressive behavior. This study shows that “proline may be causally related to depression,” said Rafael Maldonado, from UPF. Consequently, proline in the body can be considered to be the cause of depressive moods.

Continuing the study, the genetically modified fruit flies received two types of bacteria from the microbiota associated with proline consumption. However, the pathways that transport proline to the brain were blocked. The result: the amino acid couldn’t reach the brain, so the flies were more resistant to depressive moods.

According to one study, late risers in particular have a higher risk of developing depression than early risers.

Depression: study opens paths for nutrition-based treatments

The study results suggest that a proline-rich diet is associated with an increased risk of depression. “These results show the importance of proline and its influence on depressed mood in humans, which had not been taken into account before”, emphasizes Fernández-Real. Above all, the investigations would open new avenues for studies “to find potential diet-based treatments for depression.”

If you or someone you know is experiencing an existential life crisis or depression, please contact the telephone counseling service on: 0800-1110111. Help with depression and other psychological emergencies is also available at

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