Beef and fish are rich in proline, which has a strange link to mental health. Be careful with this amino acid.
A Spanish team of scientists has identified a surprising link between the amino acid prolinepresent in foods such as beef and fish, ea depression in humans, mice and flies.
The investigation, published in 2022 in Cell Metabolism, suggests that Proline-rich diets may increase the likelihood of developing depressive symptoms. The used a measurement of mood in people with diets more and less rich in this amino acid. The results were surprising.
Analysis of the participants’ blood confirmed the association: elevated plasma proline levels were among the strongest metabolic indicators linked to depression.
“We were surprised because what was most associated with depression, assessed through this questionnaire, was the consumption of proline”, explained researcher Fernández-Real.
Depression was associated not only with certain bacteria but also with microbial genes involved in proline metabolism. This means that each person’s gut bacteria appear influence how much of the proline consumed ends up circulating in the bloodstream.
To determine whether the presence of proline causes depression or if it is just a marker, the team transplanted human microbiota into mice. Animals that received microbiota from participants with higher proline levels (or with more pronounced depressive symptoms) exhibited more depression-like behavior.
“These results demonstrate the importance of proline and its influence on people’s depressive state, something that has not been considered until now”, concludes Fernández-Real.
