They say you are what you eat. But can your diet affect your mood? A new study has found a connection between a tiny amino acid, proline, and the gut that could answer this question. This link may also lead the way in treating depression.
Join us as we dive deeper into the world of proline and how this new research may have people thinking twice about their mental health and diet.
Why All the Fuss About Proline?
Proline is just one of the twenty amino acids used in living organisms as the building blocks of proteins. More specifically, it is considered an “imino” acid, similar to an amino acid. Some of the primary roles of proline include:
- Helping to form collagen
- Forming connective tissue and repairing skin damage and wounds
- Healing the gut lining and supporting digestive health
- Fighting inflammation
The human body makes some of its proline, and it is also found in certain foods such as meat, eggs, and fish. However, our need for amino acids like proline increases as we age or when experiencing specific health problems. So why are we hearing so much about this tiny amino acid lately? Researchers are now finding that for all of the positive effects of proline, this amino acid could also be linked to depression.
What New Research Reveals
While outside factors such as stress and the environment can cause depression for people, there also may be internal factors at play. Scientists at the Girona Biomedical Research Institute (IDIBGI) and Pompeu Fabra University in Barcelona, Spain, wanted to research these factors. They found that depression was linked to the protein proline in mouse models, fruit flies, and humans. More specifically, according to their findings reported in Cell Metabolism, proline-rich diets appear to increase the risk of depression. The researchers analyzed the type and amount of amino acids in the participants’ diet. Participants were also asked to complete a questionnaire to measure their mood. “We were surprised that what was most associated with depression, evaluated through this questionnaire, was proline consumption,” stated Dr. Fernández-Real, of the IDIBGI to Eurekalert.
The researchers found that bacterial genes linked to proline metabolism, which microbes would carry in the human microbiome, were also associated with depression. The proline level in circulation appears to depend not only on a diet but also on the microbes in the gut that metabolize proline. “The microbiota of patients with high proline consumption but low plasma levels of proline was similar to the microbiota associated with low levels of depression and was enriched in bacterial genes involved in the transport and metabolism of proline,” explained Dr. Jordi Mayneris-Perxachs of the IDIBGI. To determine if the presence of proline was the cause of a depressive mood, participants’ microbiota was transplanted into mice. The rodents that became more depressed had received participants’ microbiota with high proline. In addition, different genes associated with the transport of proline were also found in the brains of these mice.
The team also identified a specific microbe that was linked to depression, Enterobacter. In past research, findings have shown that people with Major Depressive Disorder (MDD) had increased levels of Enterobacter but reduced levels of Faecalibacterium (healthy bacteria) in their microbiome. These findings have given scientists a better understanding of changes in the fecal microbiota composition in patients with MDD, showing either a predominance of some potentially harmful bacterial groups or a reduction in beneficial bacteria. The fruit flies in the new study were fed these microbes, which resulted in depressive behaviors. Interestingly, when the experiment was repeated with flies that had been genetically engineered to halt the movement of proline to the brain, the depressive behaviors were stopped.
So What Does This All Mean?
Does this research mean that certain people need to give up particular foods? Change their diets? No more meat or fish? The answers are not clear – yet. More research will be required to understand this link between proline and depression. However, it’s essential to realize that when researchers studied participants’ intestinal microbiota, a relationship was observed between depression and bacteria, as well as between depression and bacterial genes associated with proline metabolism. Simply put, circulating proline levels depended on the microbiota. This has now become an exciting area to research for those with depression. It also opens the way for new studies to find possible diet-based treatments for depression.
