A host of conditions are impacted by our gut health

Get to know the many conditions affected by gut health

I hope by now that I have provided a comprehensive overview of the gut and the microbiome. In part I of this gut health series we were introduced to the gut as an organ, and in part II we looked at the microbiota. None of our body’s systems exist in isolation and the gut is no exception. As a barrier to foreign specimens entering the blood stream, the home of our immune system and the centre of waste disposal, the gut influences many health conditions. In this article I will provide a snapshot of some of those conditions dictated by our gut health – they are less obvious than you might think!

Irritable Bowel Syndrome and digestive issues

This one should be fairly obvious so I won’t spend too much time on it. If our microbiome is out of whack then our digestion is not going to perform as it should. Symptoms of imbalances are constipation, diarrhoea, gas, bloating and general discomfort. Don’t underestimate the importance of maintaining proper digestive function. It is a clear indication of the health of our gut and as the primary waste removal system is critical to good health. If we are constipated then toxic substances sit in our bodies far longer than they should. Remember our gut lining is slightly permeable so if there is waste sitting in their too long then we are not going to feel well, because particles can start to escape into our blood. Conversely, if have diarrhoea then you could be losing too much of your good gut bacteria, which can create further imbalances.

Skin conditions

Localised and chronic inflammation caused by bacterial imbalances and leaky gut can have a serious impact on the health of your skin. This is why Rosacea, a condition where blood vessels enlarge making the face red, is 10 times more common in people with SIBO. Gut flora plays a role in the types of lipids and fatty acid profiles in the body, which can influence sebum production. Sebum is the light oily substance excreted by the sebaceous glands and when we are healthy we produce adequate levels of sebum which keeps our skin and hair moisturised. However, when levels become unbalanced acne can result.

Additionally Substance P is a stress-related inflammatory neuropeptide made in the gut, brain and skin that has been linked to many inflammatory skin conditions. An altered microbiome stimulates the release of Substance P from both the gut and the skin resulting in skin issues. This neuropeptide can also affect body weight and adipose tissue. (1)

A sign that microbiota imbalances can lead to skin issues is that supplementation with the probiotics Lactobacillus acidophilus and Bifidobacterium bifidum, two strains of beneficial bacteria have been shown to improve acne.

Mental health and wellbeing

There is a strong and proven connection between the gut and the brain often referred to as the gut-brain axis (GBA). This term refers to the mutual communication between the central nervous system and the enteric nervous system. The enteric nervous system is like our ‘brain in our gut’ and is a mesh-like system of neurons with nerve cells influenced by the same neurotransmitters. Like the brain the enteric nervous system sends and receives impulses, records our experiences and responds to our emotions. (2)

As a result of this connection the gut can disrupt the brain and the brain can disrupt the gut. This is why emotional issues can sometimes manifest as digestive symptoms. Perhaps this is why we are said to ‘feel things in our gut.’ Unsurprisingly our microbiota have a profound influence on our enteric nervous system and hence the GBA.

The GBA links our brain’s cognitive and emotional functions with our microbiotic functions.  Such is the strength of this connection that, “In clinical practice, evidence of microbiota-GBA interactions comes from the association of dysbiosis with central nervous disorders (i.e. autism, anxiety-depressive behaviours) and functional gastrointestinal disorders.“ (3)

Serotonin is a neurotransmitter that helps to regulate mood, pain and circadian rhythm (sleep cycle). In the gut there are three types of cells that influence serotonin production: immune cells, nerve cells/ neurons and enterochromaffin (EC) cells. This study found mice without certain bacteria colonies produced 60% less serotonin neurotransmitters than those with the colonies. When the bacteria colonies were restored however, the mice’s serotonin production normalised again. Other studies have shown that imbalances in peripheral serotonin can cause osteoporosis, IBS and cardiovascular disease. (4)

The impacts of our gut health on our mental health should not be underestimated.


There is increasing evidence to show that obesity is directly correlated with the types of microbiota in your gut. Recent research has shown a difference in the composition of the gut microbiota between lean and obese humans and animals. An abstract from a paper published in the journal Nature stated the following:

Recent evidence suggests that the gut microbiota play a role in energy harvest, storage, and expenditure. The preponderance of the evidence demonstrates that germ-free mice are protected against obesity and that the transfer of gut microbes from conventionally raised animals results in dramatic increases in body fat content and insulin resistance.(5)

The gut microbiome is also thought to influence obesity and type 2 diabetes due to exposure to bacterial lipopolysaccharide derived from gut flora. There is now significant research under way into how we can manipulate our gut microbiota to advance weight loss and other health outcomes.

My favourite study of late suggested that THC impacts the microbiota in a way that could reduce obesity. Gut microbiota is thought to regulate endocannabinoid tone in both the GI tract and adipose tissue, which has a direct impact on weight gain. In mice that were given THC weight gain was prevented. The study concluded, “Changes in gut microbiota potentially contribute to chronic THC-induced actions on body weight in obesity.” (6)

Finally, leaky gut has been shown to increase visceral/abdominal fat, which accumulates around the organs and has been identified as a key risk factor for heart disease.

The gut- heart connection  

The inflammation caused in the gut by bacterial overgrowth and leaky gut can contribute to conditions that stem from systemic inflammation like heart disease. This study showed that intestinal permeability can increase the number of inflammatory cytokines (immune signalling cells), which in turn weakens the stability of arterial plaque. Plaque instability is a precursor to heat disease because when plague ruptures it blocks the artery and stops blood from reaching the heart. (7)

A healthy gut should produce short chain fatty acids which then circulate in the blood and prevent inflammation. However, a compromised gut will not do this effectively and reduces our body’s ability to fight inflammation.

This recent study highlighted a link between the glucagon-like peptide 1 (GLP-1) being released from the gut and the cardiac hormone atrial natriuretic peptide that lowers blood pressure. The GLP-1 receptor is used to control blood sugar in diabetics, which suggests it has a role in cardiovascular health and balance. (8)

Allergies and autoimmunity

As such a large proportion of our immune system is located in the gut the health of our microbiome will have a direct impact on conditions such as seasonal allergies, food intolerances and asthma. Allergies, like many things, go back to inflammation. If we have leaky gut and undigested inflammatory proteins can enter our blood stream, then our body will launch an immune response. The antibodies produced as a result can create symptoms are often similar to an allergic reaction, so leaky gut and allergies go hand in hand.

The types of microbes that inhabit our gut are also thought to influence our susceptibility to allergies. There is a hypothesis that suggests a lack of microbial diversity can compromise our immunity and increase our likelihood of developing allergies. This study showed that children with pets and are exposed to a wider variety of bacteria display fewer instances of allergies. (9)

This suggests that exposure to a diverse array of bacteria early in life can ‘train’ our immune system with beneficial effects on our long term immunity. In turn this can reduce our risk of allergies such as hay fever and asthma. Further highlighting the importance of microbial diversity, a recent study based on sequencing of the microbiota of children with allergies showed that they have fewer colonies of Lactobacillus and Bifidobacteria than healthy children. (10)

You may have heard of anti-histamines, medicine often used to calm an allergic reaction. Histamine is actually an essential compound produced by our bodies that acts as a neurotransmitter and is important for things like stomach acid production and contraction of skeletal muscles. As the name suggests it is also a key part of our immune response and can cause our airways to contract and our blood vessels to become more permeable, which manifests as allergic symptoms like tight throat or runny nose. Certain gut microbes produce a form of this call histamine decarboxylase. The more of these types of microbes that are present in your gut, the more histamine you will produce. This can then travel outside the gut walls and exacerbate allergic symptoms. (11)

Final words on gut health and related conditions

While not extensive, this snapshot should have illustrated the enormous diversity of the conditions influenced by the health of our gut. Contemporary research continues to find new links between illness and the microbiome, so what can we do to give ourselves the best chance of being healthy?

In part IV of this series we will look at some factors contributing to a disrupted gut and some practical ways to nurture gut health.

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