The Gut-Microbiota-Brain Connection
Are brain conditions like Parkinson’s and autism linked to the make up of microbes in our gut?
Have you heard of the gut-microbiota (the mix of microscopic organisms within the digestive tract)-brain axis and how it impacts on our health? The microbiota create their own mini ecosystem in the gut in the same way that plants, animals and insects live together in their own delicate ecosystem in a rainforest, and this complex system of resident microbes have an important role to play in ensuring healthy communication between the brain and gut. This is fast becoming the hottest of hot research fields, with more and more scientific literature providing evidence that brain-gut interaction problems have implications for a variety of health conditions, from depression to GI (gastrointestinal) disorders, to food addiction, to autism, to neurodegenerative diseases like Parkinson's disease. Described by some as the 'second brain' the gut and its connection with neurological disorders are becoming increasingly recognised. Furthermore, the gut microbiota have been found to influence intestinal development, barrier integrity and function, body metabolism, the immune system, as well as the nervous system. In fact, 90% of disease can be linked to the health of microbial relationships. With ever increasing understanding of the interdependence of our health and the health of our gut microbiota, it appears prudent that we embrace our new roles as microbiota guardians.
Gut microbiota and the immune system
These living organisms make up over 75% of our immune system and are crucial for promoting normal GI function. It is now recognised that the gut epithelium and microbiota work together to create a hostile environment for potential pathogens (harmful microbes). The immune system promotes beneficial species of bacteria which, in turn, help the growth and activation of immune cells and repel potential pathogens by lowering the pH of the gut and blocking potential sites of colonisation. The consequences of altered interactions between the gut microbe and the immune system have received particular attention recently, as disturbances in this complex dialogue have been implicated in many brain diseases. Research is currently working towards identifying possible causes for common brain disorders.
Optimal nutrition for your gut microbiota
Did you know that only 10% of our cells are human, with microbes accounting for the remaining 90%? Your gut alone hosts 100 trillion microbes, like a coral reef growing on the rugged seabed that is your intestine. One gram of faeces contains more bacteria than there are people on the earth.You are more 'them' than you are 'you.' Failure to cherish this long held extension to our own human cells (our microbes) has implications for our health. If you want to stay healthy, you need to keep your guests happy. This involves giving them the right food, hence nutrition is very important when looking to optimise the gut microbiota. Habitual diet influences their makeup. Under certain conditions, there are potentially harmful microbes that can attack your gut lining causing inflammation of the lining or ulcers. Whether or not they become harmful can be a consequence of a change in diet, antibiotic treatment or severe stress. So, put simply, of the 100 trillion microorganisms living in your gut, some are there to help, while some unfortunately, can harm. The key to achieving and maintaining good gut health, as well as good overall health, lie in making sure that your intestines are home to far more 'good' bacteria than 'bad'.
There is so much conflicting information out there. How do you decide on what eating style works best to optimise the gut's microbiota? They can adapt to dramatic changes in our food sources by changing the food they live on and the metabolites they produce. So your gut metabolites are dependent on the food you eat. You may be wondering, what do these crazy party animal microbes like to eat for tangible benefits to us? We have some way to go to know what the 'perfect' diet may be for gut health, but it will likely be very individual. The Mediterranean dietary pattern is one that stands out for the variety of foods eaten and ticks most of the boxes for a microbe friendly diet. It is a good source of fermentable fibre rich plant based foods, which provide a feast for your resident healthy gut bacteria. These bacteria metabolise the fermentable fibre into what I believe to be one of the most healing of all nutrients: (*Drumroll, please!*) short chain fatty acids such as butyrate. As well as playing a vital role in providing food for the cells lining the gut, so preventing it from becoming leaky, butyrate also enhances serotonin synthesis, protects against pathogens, modulates the immune system, reduces cancer progression and helps to mediate the cross talk between the gut and the nervous system. Furthermore, it is a key player in the communication between the gut and the brain in the regulation of food intake, creating a feeling of satiety, which prevents us from eating too much.
The human gut microbiota have the potential to produce some 500 000 different metabolites, with many of them influencing the nervous system. Evidence is building that they play a key role in a very complex signalling system that can influence every cell in your body, including those in the brain. Although we are years away from unravelling all the complex effects that these metabolites have on us, it is clear that understanding them will revolutionise the role of diet in the development and treatment of disorders of the brain and brain-gut axis. In the words of Dr Emeran Meyer, 'the orchestra of microbes in your gut is fully staffed with seasoned musicians, and ready to perform from the first years of life. The diet you choose determines not only the tune it plays, but also the quality of these tunes. And you, ultimately, are the conductor of the symphony.'