Citrus and bacteria: a natural cocktail to counter depression

Persistent sadness, long-lasting loss of interest or pleasure in activities that used to be enjoyable: depressive disorder, also known as depression, is a common mental disorder thought to affect more than 280 million people worldwide. Traditional treatments such as antidepressants often fail to produce the desired effect. Some patients even experience worsening symptoms or unwanted side effects.

What if the solution to the blues lay not in a pill, but in a bowl of fruit? A recent study ¹ suggests that oranges, lemons, clementines, grapefruit and other citrus fruits may have an antidepressant effect.

22% reduction in depression

This is the finding of a team of researchers ¹ who studied the impact of consumption of citrus fruit on depression, using data from over 32,000 women in an American cohort followed for 14 years. Their discovery? Higher consumption of citrus fruit was associated with a 22% reduction in the risk of depression.

The 20% of women who ate the most citrus fruit were far less likely to fall into clinical depression. How can such an effect be explained? By our gut microbiota, the collection of bacteria and other micro-organisms that colonize our gut, say the researchers.

A caring microbiota

So it seems that this little world that populates our digestive tract (also!) plays a crucial role in our mental well-being. And all via what scientists call the gut-brain axis. How? It would seem that flavonoids, natural substances found in citrus fruits, can modulate our gut flora, in particular by promoting the growth of Faecalibacterium prausnitzii. This bacterium is thought to be capable of producing a molecule called SAM (S-Adenosyl-L-methionine).

And here's where it gets interesting: SAM may help reduce the activity of an enzyme that breaks down the "happy hormones," in this case serotonin and dopamine. More citrus and F. prausnitzii, less enzyme destruction, more neurotransmitters available...and a happier brain!