Gastrointestinal problems such as abdominal pain, constipation or diarrhoea are common experiences for teenagers. Emotional triggers from difficult stuff: stress, exams, conflict, relationships and life changes can trigger gastrointestinal symptoms. When gastrointestinal problems continue alongside loss of appetite and/or weight loss, it’s probably time to give diet some attention. Whilst excluding medical causes for these symptoms is important,  investigations often show no obvious physical cause.  So called functional problems may be addressed with attention to diet, but also to thoughts, feelings and behaviours. This may be stress or anxiety, a personal change, emotional loss or strain, and are connected via the gut-brain axis to the the gastrointestinal tract. Butterflies in the stomach, urgent rush to toilet when stressed, noticing our gut feeling about something – you know what I’m talking about.

How the gut works – digestion and absorption

Digestion begins in the mouth, with the production of salivary amylase and continues in the stomach and upper intestine, stimulating the production of stomach acids, digestive enzymes and hormones.  Much of the nutrient absorption takes place in the small intestine with transport proteins directing the traffic of nutrients via the liver, into the circulating blood stream to muscle, bone, brain and other destinations.  Simple as it sounds, the act of chewing food well, signals satisfaction to the brain, which in turn decreases hormone production and regulates appetite. Chewing food well improves digestibility, by simply starting the process of digestion in the mouth. The small intestine can then get to work straight away, but ultimately doesn’t have to work quite as hard. More easeful. The gut illustrates its adaptive qualities by regulating nutrient absorption depending on the body’s needs.

How the gut-brain axis works

Collectively the body’s largest organ system, the gut is responsible for digestion, absorption and elimination of food and bacterial waste. Gut hormones communicate with the brain through the nervous system, using specialised nerves to transport chemical messages. These in turn stimulate production of other hormones via the brains master gland, the pituitary, acting by switching on and off other quick acting chemicals which produce physical responses. Hunger and appetite for example are switched on by ghrelin, a fast-acting hormone produced in the stomach in response to sensory influences eg. sight and smell of food, which simulates the acids and enzymes needed for food digestion. During the massive growth spurt during teens, growth hormone from the pituitary gland, provides a useful but slower-acting background message which stimulates the hunger-hormone ghrelin. Intelligent. Our gut microbiota, containing trillions of bacteria and genetic cells, facilitates this information exchange. Affected also by stimulus from the brain – thoughts, feelings and actions, by dietary intake, by stress, by genetics, back and forth in a two-way communication via the nervous system connecting gut and brain. As it has done right throughout our evolution. We are in fact more bacteria than we are human!