A journey through our gut
The gut is an emerging area of health research, and this month I read Giulia Enders, a doctor and scientist’s book ‘Gut- the inside story of the body’s most under-rated organ, to learn more and share with you what I found. If you would prefer to listen, I have recorded a podcast. Please click here.
Enders first takes us on a journey through the gut, starting at the gateway - the mouth and salivary glands. Two places I thought only to be involved with chewing and salivary enzymes. Little did I know the feats that were going on here. Each day one litre of saliva is secreted from tiny ‘papillae’ in our cheeks and beneath our tongue from the salivary glands. These produce saliva by filtering the blood, the red blood cells are filtered out, but calcium, hormones and products of the immune system enter the saliva from the blood. The salivary glands also add a few extras– the most surprising – opiorphin, a painkiller more potent than morphine, be it in minimal concentrations. It prevents already painful ulcers or mouth sores from feeling ten times worse in our sensitive mouths. When we have a more significant saliva production, such as while eating, we feel the benefit; Have you noticed a sore throat to be less painful after eating? Current research even suggests this painkiller may be an anti-depressant and reveal the science behind comfort eating.
In the mouth, the jaw, the body’s strongest muscle, and the tongue, the body’s most flexible striated muscle, work together to round up and chew our food. And at a considerable force, our jaws exert a pressure of up to 80 kilograms on each of our molars. Hence why we need tooth enamel, the hardest substance produced by the human body.
Once mushed, the tongue pushes this ‘bolus’ of food against the palate triggering the swallowing reflex. A well-rehearsed action; as an unborn baby in the womb, this is when we start practising swallowing- up to half a litre of amniotic fluid a day. Until our adult life, when we swallow on average six hundred to two thousand times a day.
The food bolus is pushed into the oesophagus and meanders through via propulsive peristalsis before reaching the sphincter muscle, the entry to the stomach. What may surprise you is how high up the stomach sits; it begins just below the left nipple and ends below the bottom of the ribcage on the right. It is a common assumption when we are in pain that it is a stomach issue; however, now you may consider that the problem is further down the gut.
If you have seen a diagram of the stomach, you may have noticed its strange shape, a ballooned J. But as we seem to be finding out with the gut, this is well-thought through. One side is much longer than the other; therefore, the liquid flows straight down the shorter right-hand side of the stomach while the food takes the longer left-hand side, allowing time for it to be churned. Once the digested food is in small enough pieces (roughly 0.2 cm), it enters the small intestine, a three- to six-metre-long organ. At first inspection of these jumbled podgy tubes, it may seem the meticulous planning and purpose that has gone into the gut so far may stop here. However, when we travel inside the small intestine, its careful crafting becomes apparent: the small intestines surface is full of folds and finger-like projections called villi—maximising the small intestines surface area. Without such designs, the small intestine would need to be 18 meters long, three times the size. Where would we fit all of that?
At the beginning of the small intestine, there is a small opening in its wall called the duodenal papilla, and through this tiny hole, digestive juices from the liver and pancreas squirt onto the now called ‘chyme’. These digestive juices contain the same agents as washing powder or washing up liquid: digestive enzymes and fat solvents. The main difference is the size of the pieces of carbohydrate, protein, or fat are much larger in the gut. The digestive enzymes snip away like scissors at these molecules until left with mother nature’s building blocks: sugar molecules, amino acids, and fats.
These energy-rich molecules are fed through capillaries in the villi to the bloodstream. Once in the bloodstream, they travel via the liver to be screened for harmful substances. After they are given the green light, the blood flows directly to the heart to be pumped out to the numerous cells of our body, and voilà energy metabolism – the sugar molecules are burnt along with oxygen, releasing the energy we need to stay alive. This is the first organ in the digestive system where we start to gain energy back into the body. For simple carbohydrates such as rice or pasta, this process in the small intestine can happen quickly, producing a rapid increase in blood sugar levels. Whereas a steak can easily take up to six hours to be processed, leaving us still yearning for that rise in blood sugar levels and often reaching for a sweet treat for a quick fix.
The final piece of the puzzle is the large intestine, framing the small intestine like a hollow podgy picture frame. It is the small intestine’s backup: further processing any leftovers of any value that may have been lost. For example, calcium, that can only be absorbed here, extra vitamins and energy-rich fatty acids. Once everything of value has been digested, the large intestine will give a hefty shove to the remaining food mush, and undigestible ruminants and the rest is history.
A remarkable process, but this is only scratching the surface as to what the gut entails. You find a whole new layer to the gut if you venture inside, undetectable to the eye – bacteria. The bacteria line the gut from the small intestine to the exit, increasing in concentration the further down, known as our gut flora.
Our gut Flora
The colonisation and shaping of our gut flora start the moment we are brought into the world. From flora in the birth canal to bacteria on the nurses’ hands and everything a baby will put in its mouth. These initial bacteria spawn within 20 minutes to produce the next generation, rapidly developing our gut microbiota. Once developed, some bacteria will stay with us for life, while some are left behind and new bacteria colonised. We dictate this: our diet and therefore the tools we need to break down certain food (for example, the gut flora of Japan has evolved to contain genes that help break down seaweed used in sushi), our lifestyles such as our stress and exercise levels, if we face illness, and the inevitable growing old. Our gut flora is constantly adapting throughout our lives and is unique to us. The bacteria that colonise our gut flora has different effects on our bodies. For example, one person may have stronger nerves than another because they have a better stock of vitamin B-producing bacteria. A person may have a greater tendency to gain weight due to ‘chubby’ bacteria that extract a greater than the usual number of calories from carbohydrates.
As an adult, our gut flora contains over one hundred trillion bacteria of over one hundred thousand different species. These are essential; our gut biome helps break down food via fermentation to supply the gut with energy. At the same time, manufacturing vitamins and nutrients, about 10% of our nutrients are from our gut bacteria. Our gut bacteria is also crucial in breaking down toxins and protecting against pathogens by occupying places harmful bacteria like to infect and making the environment unfavourable. Finally and arguably the most critical job we need out gut bacteria to train our immune system. Almost 80% of our immune system resides in the gut. Immune cells and bacteria cells live here in harmony, having been trained from existence by our gut flora to distinguish between dangerous and beneficial bacteria. This is essential as we need our healthy gut flora to help eliminate harmful bacteria.
The gut is a relatively new area of research and increasingly exciting. Recent research has shown that gut bacteria may play a part in obesity, allergies, depression and even Alzheimer’s. I would suggest reading Gut if you are interested in finding out more about these. Enders goes into detail about theories of the gut and common allergies and intolerances ( pg 53-56), on how bacteria may make us fat (pg 174-178) and the gut brain-axis and how this may be involved in depression (pg 256- 258).
Maintaining and nurturing our healthy gut flora is an integral part of our health. So how can we do this?
1. Diet
Probiotics and prebiotics. Probiotics are edible living bacteria that can make us healthier and contribute to our normal healthy gut flora. The best researched are lactobacilli and bifidobacteria. Probiotics are best used when our gut flora is damaged or altered, such as after a course of antibiotics. They are also well researched for diarrhoea, gastrointestinal diseases and immune system disorders, and there is promising research on general digestive complaints, traveller’s diarrhoea, lactose intolerance, and obesity. If you have healthy gut flora, research suggests probiotics will have little effect on the composition of your microbiome; however, increasing your consumption is thought to be safe in most cases if you are healthy. You can do this by consuming more probiotic-rich foods, including fermented foods like kimchi, kefir, sauerkraut, and yoghurt. Probiotic supplements are also available, but you should consult your doctor first.
For everyday use, Enders suggests prebiotics are more suitable. These are foods that we can eat to support our good bacteria. Harmful bacteria cannot use prebiotics; therefore, they cannot produce toxins. While the beneficial bacteria can feed on them and grow in power to take the upper hand. However, you must already have good bacteria in your gut to gain prebiotics’ benefits. Examples of prebiotics include:
- Liliaceous vegetables such as leeks, asparagus, onions and garlic.
- Compositae plants, including endives and artichokes.
- Resistance starches. These form when starch is boiled and then left to cool, for example, potato salad and cold sushi rice.
Eat more fibre. High fibre diets are associated with greater balance and diversity in the gut microbiota. Particularly beneficial are whole grains; instead of being digested in the small intestine, whole grains can reach the large intestine to feed our healthy gut bacteria. However, a sudden increase in fibre in your diet could cause bloating; therefore, you should gradually increase the amount of fibre.
Avoid processed food and those high in sugar. These have little nutrients in them that are beneficial for your gut flora. Instead, focus on eating a diet high in vegetables and healthy fats. Olive oil is particularly helpful for our gut flora.
2. Lifestyle – Exercise more and stress less. Recent research has found exercising aids a healthy gut by enhancing the number and development of our beneficial bacteria. As well as looking after your physical wellbeing, you should look after your mental wellbeing- high-stress levels can slow digestion, cause constipation and bloating or lead to diarrhoea.
3. cleanliness - Our most significant protection is cleanliness but perhaps not in the sterile, sparkly clean way we may first imagine. When we clean, often the aim is to disinfect and kill everything; but that is what you are doing, killing both the good and bad. We have an innate fear of bacteria, but 95% of the world’s bacteria are harmless to humans. Instead of eliminating everything, the aim of cleaning should be to reduce bacteria numbers; even harmful bacteria can be beneficial in small quantities for training the immune system. Enders suggests that soap and water are often enough; disinfectant does not need to be used unless a family member is sick or the dog goes to the toilet inside.
"Add life to your years & years to your life."
Written by Hope Parish
