Probiotics Learning Lab Impartially created by the experts at OptiBac

When we ask people what they associate with probiotics, the two most common answers are 'good bacteria' and 'the gut'. But what exactly is the gut and what can you do to keep it healthy?

What are the key functions of the gut?

The gut (also known as the gastrointestinal tract) is the part of the human body that runs from the top of the stomach to the anus. The body parts that make up the gut are numerous: the Stomach, Pancreas, Liver, Gallbladder, Duodenum, Small Intestine, Appendix, Cecum, Large Intestine, Colon, Rectum and Anus.

Every organ within the gut has a unique function and characteristic that helps to keep the digestive system in healthy working order. The main purpose of the gut is to take in food, digest the contents, extract and absorb energy and nutrients and then expel the remaining waste as faeces. How does this incredible system do all of that? With the help of friendly bacteria, also known as the intestinal microflora or gut microbiome.

What are the key functions of the gut microbiome?

The gut microbiome can be made up of a variety of different micro-organisms, and these generally fall into three categories: undesirable microbes known as pathogens; neutral micro-organisms which neither help or hinder their host's health, and finally desirable or 'friendly' bacteria, which are fundamental to our good health. Good or friendly bacteria are thought to help us to break down and digest our food, and to aid the absorption of nutrients. They also produce some vitamins such as vitamins B and K, and help to discourage populations of 'bad' bacteria and yeasts (i.e. Candida) from growing out of balance.

How does the gut work?

When you ingest food, water or breathe in any foreign bodies, they will come in contact with the lining of the digestive system which runs from the oesophagus to the anus. This delicate lining is made up of 3 lines of defence, the first being a thick barrier of good bacteria which physically prevents bad bacteria and yeasts from growing in the gut. This barrier also helps prevent toxins and foreign bodies passing into the blood stream.

The second line of defence are the gut cells which allow immune cells to pass from the blood stream into the gut, and vise versa. Gut cells also act as another physical barrier.

The third and final line of defence is our immune system. Up to 70% of our immune cells are located in our gut and our microbiome helps to modulate this system.

When our gut microbiome is imbalanced or unhealthy, this can lead to bad bacteria attacking and damaging the gut wall and making it more permeable. It's then easier for toxins and undigested food particles to pass through into the blood stream, and it's believed that this can result in the development of food intolerances and allergies because the immune system identifies these unfamiliar food particles as something that shouldn't be present in the blood and so it begins to attack and destroy them.
But are there other signs which might indicate that the gut microbiome is unbalanced?

What are the symptoms of an unhealthy gut?

Signs of an unhealthy gut or imbalance of good and bad bacteria can be quite subtle and may at first go unnoticed. Sugar cravings for example could seem like a normal feeling, but when looking at the symptoms all together, it's may become clear that an underlying problem is present. When your gut bacteria is imbalanced you may notice some of the following symptoms:

- Gas, Wind or Bloating
- Upset stomachs
- Sugar Cravings
- Food allergies or sensitivity
- Weight loss or weight gain
- Eczema or Dry Skin
- Trouble Sleeping
- ... and many others

Gut Health

The gut is a sophisticated and interconnected part of the body, believed to be intelligent enough to react and respond to mental and physical challenges. The importance of a healthy gut is clear when thinking about how much of the human body is made up of the digestive system: the gut is over 5 metres long, and if spread out it would cover around 30 square metres - the same as half a badminton court!2 Lifestyle factors such as stress, our diet, illness, exercise, medications, even getting older, can seriously affect the health of our gut, and the gut responses to these lifestyle factors could result in abdominal pain, bloating, nausea, indigestion, constipation, diarrhoea and flatulence (wind). This is why our gut health is so important.

Gut – Brain Axis

This is an ever growing topic of conversation that's getting more and more scientific attention. Have you ever had a gut feeling about something? Or whenever you're nervous or excited you have a feeling of 'butterflies'? This is down to the Gut - Brain Axis. The connection between the brain and the gut is a two way system that opens up communication . If the brain is thinking that we're stressed, it'll talk to the gut via the nervous system and transmit the required response. If the gut is feeling tight or stressed, it'll send signals up to the brain. This means that stress and poor mental health can affect our gut health.

What foods promote good bacteria in the gut?

When we're in the supermarket and think about improving our gut health or boosting populations of our good bacteria, most people tend to think about yoghurt drinks found in the refrigerated section. But there are many different types of food that contain good bacteria, such as fermented foods like sauerkraut, tempeh, kimchi, miso and kefir. Other foods such as beans, bananas, blueberries, polenta, Jerusalem artichokes, broccoli and other cruciferous vegetables (kale, cabbage and cauliflower) can benefit your gut because they contain prebiotics; food to keep your friendly bacteria well fed.

Fermented foods are great for overall health, but they can't be easily compared to probiotic supplements. This can be a common misconception, that we've labelled The Food Myth. The good bacteria contained within fermented foods will vary, both in the numbers present and the type of bacterial strains, so you can't compare this to a good well-researched probiotic supplement which should tell you exactly how many bacteria you're consuming, and which strains of bacteria they are. This in particular is important information because it's advised to choose the best strains of bacteria for your individual health needs. The number of microorganisms in commercially-available (or homemade) fermented foods is often undetermined, and almost certainly thought to be lower than those found in probiotic supplements, and you don't always know which strains of bacteria you're consuming.

Gut Health Checklist

1. Keep the gut (and the rest of your body) well nourished and hydrated by drinking plenty of water. This will help to improve and maintain the heath of your gut, by flushing out any unwanted toxins, undigested food etc.

2. Eat foods that are rich in fibre. Beans, nuts, seeds, whole-grains, fruits and vegetables. These all help to feed the good bacteria in your gut.

3. Try and limit sugar intake, as well as processed foods, animal fats, and animal protein - these can act as food for unhealthy bacteria that can harm your gut.

4. Improve your levels of good bacteria by introducing daily probiotics into your diet. Having healthy, friendly, good bacteria can improve your digestive health and reduce inflammation and allergies.

Gut Health Checklist
Gut Health Checklist - What you need to know
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1. Sender, R. et al (2016) Are we really vastly outnumbered? Revisiting the ratio of bacterial to host cells in humans. Cell. 164. 337-340
2. Helander, H. F. & Fandriks, L. (2014) Surface area of the digestive tract - revisited. Scandinavian Journal of Gastroenterology. Vol 49: 6.

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