An estimated 3.8% of the world's population suffers from depression, including 5.0% of adults and 5.7% of persons over the age of 60. Around 280 million individuals worldwide suffer from depression according to the Institute of Health Metrics and Evaluation, Global Health Data Exchange (GHDx) (Accessed 1 May 2021). According to the World Health Organization(WHO), depression is the greatest contributor to disability globally.

Depression is also known as clinical depression or major depressive disorder which is a mood disorder that causes a prolonged sense of sadness and loss of interest in formerly fulfilling or joyful activities, concentration issues, and exhaustion. It can cause a number of emotional and physical issues by affecting a person’s ability to feel, think and behave. It becomes difficult for an individual to carry out their daily tasks, and they might occasionally think life isn't worth living.

A person's efficiency to operate and lead a fulfilling life can be significantly affected by the long-lasting or repeated impacts of depression.

Depression can be caused due to

• alterations in neurotransmitter levels in the brain

• genetic traits

• environmental, social, and psychological factors.

• Any trauma or lack of social connection or support

• Bipolar disorder

• Childhood hardship, loss of loved ones, and unemployment are all factors that can contribute to and/or hasten the onset of depression.

• Diet and lifestyle for example, a Proline-Rich Diet May Elevate Depression Risk

Proline

Proline is a non-essential amino acid that helps in making collagen protein that creates connective fibers in our skin, bones, and muscles.

As it is a non-essential amino acid, it is produced by our body in an adequate amount, therefore, it is not necessary to consume it daily. However, it becomes an essential amino acid during times of stress, growth, or healing as our body utilizes all of the proline present in the body and requires more amount of it.

Proline and its relation with depression

The study, published in the scientific journal Cell Metabolism, conducted by researchers from the Girona Biomedical Research Institute (IDIBGI) and Pompeu Fabra University (UPF) in Barcelona, Spain reported that proline may be associated with severe depression.

For this study, a multi-omic approach was used by researchers. The kind and quantity of amino acids in the study participant's diets were first examined. They also examined participants' blood plasma and feces samples. For this study, 100 subjects were selected and divided into three categories according to the level of depression i.e non- depressed, mild, or majorly depressed.

The strongest correlation between proline levels in the body and depression scores was discovered by researchers through metabolite profiling.

For knowing how the proline was there in their body in increased amounts, researchers also used questionnaires that contained details on the diets of participants. It was found that people with more severe depression had greater plasma proline concentrations, which indicated that the proline in their diets was not properly metabolized.

The outcomes, according to Fernández-Real and Verywell, were extremely unexpected. He claimed that in seemingly healthy participants, "proline consumption was the most related item with the depression score."

For gut bacteria testing the human subject, gut bacteria were transplanted into mice. The mice that received the bacterium with the highest proline content had the most signs of depression.

Fruit flies were used in the study's last step. The flies that got proline-rich bacteria showed depressive symptoms just like the mice did.

Fernandez-Real noted that the research team did observe that some subjects with a high intake of proline were not depressed because in those subjects the level of proline in plasma was not high as their gut microbiota metabolized proline.

Summing Up

Some people showed an elevated risk of depression with proline while some didn’t due to the microbiome effect, as there are other factors also involved in depression along with diet. Therefore, it is not advised to avoid food that contains proline completely until recommended by a physician.

As Dr. Tsai stated, "Based on this study, I don't think there is enough evidence to conclusively correlate dietary proline levels with depression. It is worth investigating more diligently with a human experiment that is randomized, controlled, prospective, and double-blinded,”

However, the study paves the way for additional research to discover potential diet-based depression treatments.

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