Bacteria is most densely populated in the gut, especially in the colon, this community of bacteria is called the gut flora or microbiota. There are around 1,000 different bacterial species which can live inside the gut, with about 100-150 at any one point in time. Most of these species work symbiotically to support good health. The diversity and number of bacteria are affected by environmental factors such as diet, stress, and physical activity. One of the fascinating things about gut flora is that everyone has a unique combination of bacteria, therefore, there is not a magic solution which suits everyone. However, research has shown that having a healthy diet and being physically active will support your gut bacteria.

The Role of Gut Bacteria

1. Bacteria helps to digest food and absorb nutrients. For example, gut bacteria can break down dietary fibre (parts of cereals, fruits, and vegetables that we cannot digest) and use this as energy. A diet rich in dietary fibre has been linked to having a more diverse gut bacterium. Furthermore, when bacteria break down dietary fibre, short-chain fatty acids (SCFAs) are produced. SCFAs are used in the body in several ways, for example, they help to reduce the risk of developing colon disorders, they are used by the brain, muscles, and body tissues, help to lower cholesterol, and lower blood sugar levels. 
2. Bacteria produce many vitamins which the body absorbs and uses. For example, bacteria produce folate, vitamin B2, B3, B12 and vitamin K. Vitamins are essential for health, for example, vitamin K aids healthy blood clotting in the body.
3. Gut bacteria help to boost the immune system. It does this by killing harmful bacteria, reducing the amount of harmful molecules ‘leaking’ into the bloodstream, and stimulating cells which fight infection.

Gut Flora and Our Health

Looking after your gut bacteria supports long-term health. In recent years there has been a plethora of new information discovered about the gut and how it affects our health and wellbeing. Gut flora has been found to influence many conditions such as obesity, diabetes, heart disease, IBS and colorectal cancer. The bacteria in our gut have also been linked to brain functions, this is called the gut-brain axis. Changes in the brain can cause changes in the gut, and vice versa. These changes have been found to influence cognition and mood. New evidence suggests that the gut flora acts as an essential mediator in the gut-brain axis. The SCFAs that gut bacteria produce, protect the brain from inflammatory damage which has been linked to depression. Furthermore, serotonin plays a critical role in the gut-brain axis. Most of our serotonin is made in the GI tract, therefore, if the gut flora is not optimum this can affect serotonin production leading to mood disorders.

More research needs to be completed for us to fully understand gut bacteria and how this leads to different health conditions. However, research suggests that diverse and stable gut flora can help to alleviate symptoms of conditions.

Looking After Your Gut Flora

The key to optimum gut health is ensuring the gut flora is diverse; having a wide range of bacterial species which carry out a variety of functions. How do we look after our gut flora? The short answer – eat a healthy, balanced diet containing a variety of foods, especially those rich in fibre. High intakes of any one nutrient (such as too much protein or fat) can affect the growth of different bacteria in the gut. Studies have shown that changes in the diet result in very fast changes to the gut flora therefore quick changes can make a big difference.

As discussed previously, fibre is vital for gut health as it provides food for bacteria, allowing them to grow and thrive. The current guidelines recommend having 30g of fibre a day, however, people in the UK are only getting about 20g. you can boost your fibre content by 6g a day by having a bowl of high fibre cereal or 2 slices of wholemeal bread. It is important to remember that it is not only cereal fibre that can assist with gut health, but fruits and vegetables too.

Here are some quick dietary and lifestyle tips to help your gut bacteria thrive:

• Avoid highly processed foods. These types of foods often contain ingredients which suppress the good bacteria or increase the bad bacteria. A diet rich in these foods has been linked to reduced diversity of gut flora particularly due to the lack of fibre. 
• Have probiotic foods, such as live yoghurt. Probiotic foods allow microbes to grow but only whilst you continue to take them. 
• Choose extra-virgin olive oil. Extra-virgin olive oil contains the highest number of microbe-friendly polyphenols, compared to its counterparts.
• Be physically active. Physical activity increases gut flora 
• Limit your alcohol intake. Alcohol negatively affects gut flora. 
• Avoid taking antibiotics where possible. Antibiotics decrease the amount of gut flora. Of course, this cannot always be avoided so make sure to eat lots of foods which boost gut flora if you are taking antibiotics. Research has shown having probiotics whilst taking antibiotics (taken as soon as you start the antibiotics and continue for at least one week after the end of the course) helps to prevent diarrhoea.

Probiotics vs prebiotics 

Probiotics are foodstuff or supplements that contain live bacteria which are thought to improve the balance of our gut flora. Examples of probiotics are yoghurt, some cheeses, and fermented foods. However, if you have a compromised immune system, it is important to speak to a professional (i.e., a dietitian) before having probiotics.

Prebiotics are foods that ‘fertilise’ the gut bacteria already existing in the gut as well as help to diversify the community of microbes. Prebiotics are complex carbohydrates (e.g. vegetables and whole grains).

Foods for ‘Gut Health’

Many foods are promoted as ‘healthy for your gut’, but what is true and what is just a marketing technique? One of the most popular ‘gut healthy’ products is fermented foods such as kombucha, kimchi and sauerkraut. Countries, where these foods are eaten regularly have been found to have better gut health and less bowel disease, however, we cannot be sure whether if other environmental factors play a part. You might have also been promised incredible gut health from taking probiotic supplements, however, there is not enough evidence to support that the bacteria in these supplements reach the gut.

 Take Away

Plenty diverse gut bacteria are vital for physical and mental health. Eating a healthy, balanced diet and being physically active can ensure you have sufficient gut bacteria.

A few things from Susan's favorite page to help with gut health

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