I’ve been making my own yogurt on and off for years (didn’t take me for a hippy did you?) I’m a kiwi and many families have an EasiYo system. Well, system makes it sound way fancier than it actually is … I just pop the culture mix and water into a jar, and then put that into an insulated yogurt maker … leave it to culture overnight and voila – yummy fresh yogurt complete with billions of probiotic microbes to boost my gut health.
There are plenty of reasons why probiotics are good for you – we need a delicate balance of good bacteria in our intestines to maintain healthy metabolism, immune function and digestion. But the crucial role that gut bacteria play in the health of our brains is something I never knew about until recently.
Two Irish neuroscientists John Cryan and Timothy Dinan (love the Irish!), recently wrote a review of the neuroscience of the gut-brain connection in Nature Reviews Neuroscience (note: this is a high quality neuroscience publication) and the message they conveyed really surprised me…
Gut microbiota communicate with the brain — possibly through neural, hormonal and immune pathways —to influence brain function and behaviour
An overview of the gut-brain connection
- a healthy balance of gut bacteria contributes to normal behaviour, cognition, emotion and a well-functioning immune system.
- poor balance of the bacteria (perhaps brought on by stress, disease or antibiotics) disrupts the gut-brain signalling pathways.
- disruptions in gut-brain signalling may lead to abnormal brain function, changes in our behaviour, thoughts, emotions, our perception of pain, and may also impact our immune system.
Everyone has a different composition of good gut bacteria, but there are three typical communities (enterotypes) with each community is made up of a single microbial genus: Bacteroides spp., Prevotella spp., or Ruminococcus spp. The food we eat is one of the main factors that can affect the composition of these populations
Fascinating fact alert – our gut is inhabited by 10 times more bacteria than there are cells in our entire body?!
Gut microbiota and brain health
The hypothalamic-pituitary-adrenal axis in the brain is a circuit that controls reactions to stress (as well as regulating functions like digestion, the immune system, mood and emotions). Chronic stress affects gut bacteria composition, and in return, gut bacteria directly influence the development of the brain’s appropriate stress response.
Both the central and peripheral nerve pathways that sense visceral (abdominal pain) can be affected by intestinal microbes. Some strains of Lactobacilli and Bifidobacteria can alleviate the pain caused by irritable bowel syndrome and stress.
MS is a devastating autoimmune disease that is characterised by the progressive deterioration of neurological function. Gut bacteria may have a role in the development of MS.
Depression and anxiety:
The neuroscience of gut health and more serious mood disorders is very new, but Profs Cryan and Dinan suggest that as our understanding grows, modulation of the gut microbes may become part of a strategy for developing treatments for complex brain disorders. They have found that brain levels of serotonin, the ‘happy hormone’ are regulated by the amount of bacteria in the gut during early life.
What about probiotics and the gut-brain axis?
Probiotics are live organisms that, when eaten in adequate quantities, exert a health benefit. There is a reasonable amount of clinical evidence supporting the use of probiotics. In lab animals, probiotics have been shown to reduce anxiety- and depression-like behaviours and prevent stress-induced increases in the stress hormone cortisol.
And, if you’re particularly interested in neuroscience (and of course you if you’re still reading!) probiotics can alter the expression of BDNF levels (a brain chemical involved in neuron growth) and GABA receptors (a type of ‘lock’ that brain chemicals latch onto)
At the end of the paper Profs Cryan and Dinan conclude….
…it is becoming increasingly apparent that behaviour, neurophysiology and neurochemistry can be affected in many ways through modulation of the gut microbes…
Cool huh? I’m off to make some yogurt.