Gut health


There are trillions of microbes that live in our gut and many of them are beneficial. They break down the food we eat, providing us with energy and vital nutrients we need for maintaining a healthy body. This includes our skin, brain, heart and immune system. They also help us get rid of waste and manage our weight. By eating the right foods you can help the good bacteria to grow and keep yourself healthy.

Your gut and your microbes

There are more microbes than human cells in the body. The human gut contains microbes including bacteria, archaea, viruses and fungi with bacteria being the most numerous. Everyone’s microbiota (the community of microbes that live in your gut) is different, in the same way that a fingerprint is unique.

The trillions of microbes living in your gut can be classed together in different groups, and in general the more different groups there are, the healthier it is for us. This is because each group of microbes performs a different role or function and if one group is missing then that function could be missing too.

Gut microbes and your health

We used to think that our gut microbes were only important to help us digest food and to keep the gut healthy. In the past two decades scientists have discovered that they do much more than this, and in fact the products released by our gut microbes are absorbed and circulate all round our body. Some scientists have even described the gut microbiota as the “forgotten organ” meaning that it is as important for us as our heart, lungs and liver. So a healthy gut really does make a healthy person.

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Your diet and your microbes

All the bacteria and other microbes that live in our gastrointestinal tract, or gut, depend on our food for their food. Since there are so many different microbes present, they all have different favourite foods so it is important to eat as varied a diet as possible to make sure that they all get enough food to grow. When the anaerobic bacteria (bacteria that cannot grow in the presence of oxygen) that live in the large intestine digest their food the process is called bacterial fermentation. Generally the bacteria that are good for us like to ferment carbohydrates and fibre, while the ones that might not be so good for us are good at digesting fats and protein.
Changing the food we eat is one very quick way to change the types of bacteria present– the composition of our gut microbiota.

Probiotics and Prebiotics

Probiotics are defined as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host". Probiotics are often found in dairy products such as yoghurts or can be taken as tablets.

A prebiotic is defined as "a substrate that is selectively utilized by host microorganisms conferring a health benefit". Prebiotics are naturally found in some vegetables and can also be added (supplemented) to food products or taken as pills.

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Gut microbial communities

Bacteria on faecal fibre
Bacteria on faecal fibre. Dr. Alan Walker, The Rowett Institute.

The many different bacteria that live in our gut exist together in communities, and the products of different bacteria can affect other bacteria. These can be both positive and negative effects. An example of a positive bacterial interaction is when one bacterium chops up a complex carbohydrate substrate releasing shorter molecules that other bacteria can use for food. Microbes also work together to keep conditions such as oxygen level or pH optimal for their survival. Sometimes the products released by some bacteria can be bad for different bacteria living in the gut but if the affected bacteria are harmful, this can actually be good for us.

Meet your gut bacteria

The most numerous microbes in the gut are bacteria, and they are often referred to as “good bacteria” because many of them do jobs like help to digest our food and keep us healthy. Here you can learn about many of these bacteria and the important roles that they play. You can also find out about some of the “bad bacteria” that can make you ill.

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Antibiotics and your gut

When we are ill and go to the doctor, we often get a prescription for antibiotics to make us feel better. Antibiotics are really good at stopping bacteria from growing and even killing them – which is why they are good to make us feel better quickly, if our infection is caused by bacteria.

Unfortunately since the doctor does not always know exactly what type of bacteria is making us sick, they will give us an antibiotic that kills as many bacteria as possible – and this includes killing many of the bacteria that live in our gut to keep us healthy. This is one reason why we should only take antibiotics when we really need to.