Gut bacteria part 2: The whole-body effects of your gut bacteria

How can the content of our gut influence the rest of our bodies?

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Nutritional Practitioner, BA (Hons), DN, DNT (Distinction)
Ask Ali

27 September 2017

An introduction to the effects of gut bacteria

So, you now know that you have lots of bacteria in your gut. 

Although you might assume that they are so microscopic, you don’t even notice that they are there and they can’t be having much of an impact... there is growing evidence to suggest that the balance of bacteria in your gut might be having more of an influence than we previously thought – both within the gut and elsewhere around your body.

Mental health

Your gut is thought to have links to many parts of your body and the brain is definitely one of them.

Your gut and brain are closely linked. The gut has its very own nervous system (the enteric nervous system) which effectively communicates with your central nervous system and its main functional unit – the brain. For this reason, you often hear of the ‘gut-brain connection’. 

The feel-good neurotransmitter serotonin is particularly abundant in the gut and this has an important role in influencing your mood. This link between the gut and the brain and the influence of serotonin appears to be significant as is apparent in certain scenarios.

For example, a certain class of anti-depressant medication known as selective serotonin reuptake inhibitors (SSRI) have been found to exert a positive influence in the gut of people with Irritable bowel syndrome (IBS). 

On the flipside of this, changes in the gut can affect your mood, for example in constipation. If you are constipated, old food waste which should have been excreted is left sitting in your gut. The toxins which would have normally left your body long ago are left lurking and can be reabsorbed back into your body (remember the large intestine is very good at reabsorption; usually of beneficial substances such as water though!). It appears an overload of these toxins as a result of constipation can give rise to irritability and even depression in some cases.

So, is it possible that the state of your gut can influence your mood? It appears so. Research in this field is advancing and there is some evidence to support this. Different strains of bacteria can negatively affect the central nervous system too and may be contributing to problems such as anxiety, autism and depression. 

In addition to this theory, if you have an overgrowth of bad bacteria in your gut, you are likely to experience some unwelcome symptoms including bloating, flatulence, stomach pain, constipation or diarrhoea. 

Some of these symptoms can be extremely debilitating and can impact your life in more ways than one; your mood being one of them. Digestive system issues and low mood can operate in a vicious cycle, with physical symptoms affecting your mood and on the flipside, if you are feeling particularly anxious or stressed; this can exacerbate your symptoms!

Immune system

Up to 70% of our immune cells are found in the gut. Therefore, to some degree you can assume that the immune system is reliant on the health of your gut!

We know that beneficial gut bacteria help in the development of many of your immune cells. This is particularly important in babies and young children but continues to some extent throughout the course of your life. 

In good health, the gut wall is important as it forms an effective barrier against pathogens. However, in certain circumstances, such as when you have an imbalance in your gut bacteria, this can become disturbed. This means that invading pathogens suddenly pose more of a threat. If toxins produced by bad bacteria, or the pathogens themselves, manage to bypass our defences then your immune system must recognise this and step in. 

Gut bacteria imbalance (dysbiosis) can give rise to ‘leaky gut.’ This state changes the structure of the inner cells of the gut, meaning they no longer stand tightly together; instead big gaps form between them. This means pathogens can more easily leak through into your bloodstream and your poor immune system can become over whelmed, struggling to keep them under control. 

This scenario results in an over-stimulated immune system which can create further problems. We are left with an immune system which is not only over-active but also less efficient at managing the pathogens we actually need protection from! This can make you more vulnerable to infections, such as colds or flu.

Food intolerance, allergies and skin health

Food intolerance or allergies may manifest as a result of an over-active immune system as your body’s defences begin to attack any substance that appears to pose a threat – even something as harmless as your lunch!

The exact causes of food allergies aren’t well understood and they are thought to be the result of a combination of environmental and genetic factors. Food intolerances, on the other hand, have sparked particular interest in recent years as they are becoming more common and appear, in many cases, to develop over time. Allergies are a result of your immune system over-reacting to harmless dietary or environmental triggers; food intolerance is also thought to involve the immune system, mounting a low-grade, inflammatory response.

Food intolerance often comes hand in hand with problems in the gut. As dysbiosis can affect the integrity of the gut wall, partially undigested food particles can more easily come into contact with the immune cells residing there. 

Interestingly, food intolerance is particularly apparent in response to a category of foods called FODMAPs. These foods remain partially indigested until they reach the large intestine. Here they are detected by your immune system and especially if it is inclined to over-react; symptoms of a flare up can appear before we know it.

Skin issues are also thought to be linked to unhappy gut in many cases.  Food intolerance or allergies (often thought to manifest as a result of dysbiosis) activate your immune system, therefore increasing systemic inflammation which can give rise to skin flare ups. Eczema is commonly linked with food sensitivity and is characterised by of a thickening of the skin –excess histamine that results from an inflammatory response. 

If you have eczema, you will often find you have weak stomach acid to go with it. Low levels of stomach acid can be the root cause of many issues and can affect the digestion of certain foods, (particularly those high in fat and protein such as dairy products) not to mention the overgrowth of bad bacteria. 

This means skin issues such as eczema are often exacerbated by some common dietary factors including dairy (not well digested), refined sugar (feeds the bad bacteria) and food additives which can aggravate the gut further and give rise to issues such as leaky gut. 

Regaining balance in your stomach and your gut is often a useful first step in keeping skin conditions such as eczema under control.

Digestive health 

As well as bacterial overgrowth, yeast proliferating in the gut can also cause us issues; a common example is that of Candida albicans. 

Candida is yeast which is naturally occurring in the gut and is not a problem if kept in balance. However, in certain conditions, Candida takes the opportunity to over-populate. What we eat is important; sources of refined sugar can basically feed the Candida and doesn’t offer your good bacteria the support it needs (unlike complex carbohydrates rich in B vitamins). 

How you eat is also worth considering; if you eat too quickly (and especially if this is coupled with low levels of stomach acid) you risk not digesting your food properly. This can act as a convenient source of fuel for the yeast living in your gut. 

The over-use of antibiotics is also a cause for concern. Antibiotics can alter your levels of good bacteria which are crucial for controlling the bad bacteria and yeast in your gut. If the levels of your friendly gut bacteria diminish at the hand of antibiotics, the candida can take advantage and flourish.

Candida can effectively pierce the gut wall, allowing toxins to pass through. These can circulate in your blood, making their way around your whole body. Candida albicans can give rise to thrush and can even cross the blood-brain barrier and symptoms such as brain fog can be a result.

Bloating is a classic symptom of dysbiosis to look out for too and again, may also be linked to issues with stomach acid. If food isn’t effectively broken down initially in the stomach and by the action of pancreatic enzymes (which are also partly stimulated by stomach acid!) then the bad bacteria in your gut can make their move. As bacteria feast on the remains of your lunch, they produce gas and you can easily become bloated.

Finally we have IBS. Amongst other causative factors, we now have reason to believe that the balance in your gut could be having an influence. Research suggests that taking a course of probiotics could even help to ease some of the symptoms! It seems that keeping the bacteria in your gut happy could really make a difference to those suffering from this debilitating condition.

In summary...

I think it’s safe to say that the bacteria in your gut can exert effects in more places than one and have a scary influence over so many of our bodily functions. It’s so important to try and keep your good bacteria happy and in balance to avoid the longer term effects of bacterial imbalance.

For part 3 of my good gut bacteria series: 'How to keep your bacteria in balance' click here.

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