Human cells make up less than half of what you call ‘you’ – the rest are trillions of bacteria, fungi and viruses in your gut, on your skin and throughout your tissues, collectively known as your microbiome. You need them because of the role they play in digesting your food and maintaining a healthy immune system. They need you because they need somewhere to live.

Psychobiotics is a term used in research to refer to live bacteria that, when ingested in appropriate amounts, may confer a mental health benefit by affecting microbiota of the host organism. In mainstream media we are beginning to read more and more about it now in the where the terms used are usually gut health, or digestive health

Epidemiological researchers have turned up intriguing connections between gut and brain disorders. For example, many people with irritable bowel syndrome are also depressed, people on the autism spectrum tend to have digestive problems, and people with Parkinson’s are prone to constipation.

Researchers have also noticed an increase in depression in people taking antibiotics—but not antiviral or antifungal medications that leave gut bacteria unharmed. While research is only in its infancy a growing number of researchers see a promising alternative in microbe-based treatments, or “psychobiotics”.

One thing that we do know for certain is that psychiatrists and dietitians have, for years, been saying that changing our eating habits can make us happier, or at least help keep us on an even emotional keel.

Leading neuropharmacologist John Cryan and psychiatrist Ted Dinan, both at University College Cork coined this term Psychobiotic. The reason I became interested in the whole area is because in their book The Psychobiotic Revolution they recommend “Up Your Intake of Yogurt, The Best Know Pyschobiotic”

Yogurt has been recognised as a healthy food for thousands of years.  Yogurt and other fermented milk products are made by introducing bacteria, including psychobiotics such as the Lacto and Bifido species , into the milk and providing the best circumstances for them to multiply. Lacto species eat lactose, which is milk sugar. Once fed, they produce lactic acid , which sours (or ferments) the milk. If you are lactose intolerant, you may find that you can eat yogurt because the Lacto species have eaten most of the lactose for you.

But you may not be lactose intolerant, you may in fact be intolerant to A1 protein, which is the protein found in cow dairy products. This is why many people who find they are intolerant to dairy, can still consume sheep’s dairy, because sheep’s milk contains A2 protein.

So all these terms “Listen to your gut” “A gut feeling” “You are what you eat” “Food is medicine” are all beginning to make more sense now.

 I continue to research more...


Sarkar A, Lehto SM, Harty S, Dinan TG, Cryan JF, Burnet PWJ. Psychobiotics and the Manipulation of Bacteria-Gut-Brain Signals. Trends Neurosci. 2016;39(11):763-781. doi:10.1016/j.tins.2016.09.002

Aisling Flanagan