Areas › Your body › Food, caffeine and fuel
Your gut is not just plumbing. It makes many of the same chemicals your brain runs on and it is in constant conversation with your nervous system, which is part of why a bad stretch of digestion and a low mood so often turn up together.
If your stomach has been unsettled for weeks and your mood has slid over the same weeks, you do not have to work out which one is the real problem. They are wired to each other. Worth mentioning both to whoever is helping you, even when it feels like you are describing two separate appointments.
Qur’an and Sunnah
From their bellies comes a drink of different colours in which there is healing for people (Quran 16:69). What the body takes in is treated as bound up with how well a person is, not as a separate matter.
ثُمَّ كُلِي مِن كُلِّ ٱلثَّمَرَٰتِ فَٱسۡلُكِي سُبُلَ رَبِّكِ ذُلُلࣰ اۚ يَخۡرُجُ مِنۢ بُطُونِهَا شَرَابࣱ مُّخۡتَلِفٌ أَلۡوَٰنُهُۥ فِيهِ شِفَآءࣱ لِّلنَّاسِۚ إِنَّ فِي ذَٰلِكَ لَأٓيَةࣰ لِّقَوۡمࣲ يَتَفَكَّرُونَ
Then feed on all kinds of fruit and follow the ways made easy for you by your Lord.’ From their bellies comes a drink of different colours in which there is healing for people. There truly is a sign in this for those who think
Qur’an 16:69read it in the library
Translation: M.A.S. Abdel Haleem, The Qur'an, Oxford University Press, 2004.
What the research says
In a randomised trial, healthy volunteers who took a multi-strain probiotic for four weeks showed changes in resting brain connectivity compared with placebo. That is a brain imaging measure rather than a mood measure, so it hints at a real pathway without showing that anyone felt different. Read it as evidence the connection exists, not as a reason to buy a supplement.
Bagga D, Aigner CS, Reichert JL, Cecchetto C, Fischmeister FPS, Holzer P, Moissl-Eichinger C, Schöpf V. (2019). Influence of 4-week multi-strain probiotic administration on resting-state functional connectivity in healthy volunteers.. European journal of nutrition doi
Strength of evidence: one line of research. A single study, or a theoretical account.
Why it works
The gut and the brain send signals to each other all day, so trouble in one usually shows up in the other.
This one is still a draft. It is waiting on a scholar and a clinician to read it before it is published.
Near this one
Even where a herb has good evidence behind it, that evidence belongs to the plant and not to the bottle in your hand. Testing keeps turning up products that do not contain what the label says.
Most claims about food and behaviour rest on weak studies. The ones worth taking seriously give each person both the real thing and a dummy at different times, with nobody knowing which is which, so that hope and expectation cannot do the work.
Two to be careful with in particular. Yohimbe reliably ramps anxiety up, so much so that it has been used in research to bring panic on, and kava is a sedative that stacks with alcohol and with sedating medication and has damaged livers at higher doses.