19 Impacts of Gut Bacteria on Health and Diseases

impact of gut bacteria on health and diseases

A gut flora imbalance or intestinal flora imbalance describes the condition where the balance between good and bad bacteria in our gut gets out of whack.There has been a mountain of research conducted in recent years linking a host of medical conditions to the activities and balance of our gut flora. For years, science has paid little attention to the 100 trillion microbes that inhabit the dark corners of our gut. But now the floodgates have opened as researchers realize that our gut bacteria are not simply a passenger in our gut, but interact with our body and help regulate just about every aspect of our physiology. To put it simply, gut bacteria or intestinal flora, are so important that if there is a gut flora imbalance, the system fails. The impacts of gut bacteria on health and diseases have never been so important. Check them out.

Diseases from a gut flora imbalanceImpacts of gut bacteria on health and diseases

1. Immune system

When most people think about the immune system, vaccines, glands and white blood cells spring to mind. Most would be surprised to learn that our intestines are where the real action takes place as they contain more immune cells that the rest of the body put together. Not only do our gut bacteria help digest food, but it is postulated that there is ‘cross-talk’ between the microbes in our gut and other cells in the body responsible for the immune system and metabolism.

The true extent of the impact of gut bacteria on health via the immune system is only just being realized. When there is a gut flora imbalance, this feeds through to our immune system, leaving the body open to pathogens and autoimmune diseases. (1)(2)

2. Irritable Bowel Syndrome

Irritable bowel syndrome is a common and long-term condition of the digestive system. Its symptoms are diarrhea, stomach cramps, bloating and constipation.

The symptoms vary between individuals and affect some people more severely than others. They tend to come and go, with symptoms lasting a few days to a few months at a time.

Overgrowth of gut bacteria in the intestines and the subsequent gut flora imbalance has been linked to the condition. The study that proved this studied small bowel cultures from the intestines of people suffering from irritable bowel syndrome. Of the 320 people involved in the study, over 30% of the subjects had an overgrowth of bacteria as compared to ten percent in people without irritable bowel syndrome. (3)

3. Inflammatory bowel disease

Inflammatory bowel disease (IBD) is considered an autoimmune disease which describes two similar conditions, Crohn’s disease, and ulcerative colitis. Both are long-term conditions involving the inflammation of the gut. Crohn’s disease can affect any part of the digestive system while ulcerative colitis usually only affects the large intestines.

Symptoms of the disease include stomach cramps, weight loss, tiredness and chronic diarrhea.

Research has shown that certain gut bacteria interact with the lining of the gut wall and influence how the wall regenerates. This regeneration is called epithelial cell shedding, and the process is vital to maintaining a healthy gut lining.

The bacteria help regulate how quickly new cells replace old cells. However, in patients with IBD, the shedding process happens faster than cells can be replaced, leading to a ‘leaky’ gut barrier.

Research has shown that patients with inflammable bowel syndrome typically have less biodiversity in their gut bacteria, and are depleted in certain bacterial species. But until now, we have had only limited insights as to why this is important in the context of disease. (4),(5)

4. Infant Colic

Colicky babies are babies who cry for more than three hours a day for no apparent reason. Nobody knows what makes some babies colicky while others aren’t. However,  a study run on colicky babies showed that they had a higher volume of Proteobacteria in their gut than babies without colic. This bacteria is known to produce gas which was probably why the babies cried so much. (6)

5. Diabetes

Diabetes is a condition where the body has trouble processing food for energy. Patients with diabetes either produces insufficient insulin or develop insulin resistance, a hormone used to convert food to energy.

The current consensus is that the major contributor to insulin resistance is excess weight and a sedentary, inactive lifestyle. However, recent research has now linked a gut flora imbalance to insulin resistance, a precursor to type 2 diabetes. (7)(8)

6. Metabolic Syndrome

Studies involving both humans and mice have confirmed that gut flora have a direct effect on metabolic syndrome. The bacteria in your gut is responsible for balancing out how your gut metabolizes and absorbs food. An imbalance between the host’s immune system and the bacteria that line the gut results in inflammation and insulin resistance which wreck havoc on host’s metabolic rates. (9),(10)

7. Obesity

An ever-increasing number of scientific studies is showing that gut bacteria can have a direct effect on a person’s weight. One of these studies showed that obese people have a gut flora imbalance and in particular, less diversity in their gut bacteria than lean people do. The prevalence of Firmicutes and lower levels of Bacteroidetes bacteria, in particular, is found among obese people. (11)

Separate studies run on mice suggest the same thing. One study such study transplanted fecal samples from obese mice and transplanted them into lean mice. After the transplant, the formerly lean mice gained mass rapidly.

8. Heart Disease

When gut flora digests certain foods such as beef and eggs, they produce compounds which increase your chances of heart disease. This compound is called TMAO, and it can cause blocked arteries. Patients with high levels of TMAO in their bodies are two times more likely to have a heart attack or suffer from a stroke.

The gut bacteria of omnivores and vegans was also compared, and researchers found an increased production of TMAO in omnivores.

Results to support this claim are still preliminary however it reinforces what we know about how eating certain animal products. The research though does suggest that the link between red meat consumption and heart disease is related to a gut flora imbalance. (12)(13)

9. Brain development and function

Research on gut flora is producing mounting evidence that there is an interaction between the functioning of the gut and brain development and activity. It has even been dubbed the gut-brain axis!

There is increasing evidence pointing to a relationship between the central nervous system and the balance of the gut flora. A gut bacteria called Lactobacillus rhamnoses is suspected of having a direct effect on neurotransmitter receptors in the nervous system.

Likewise, microbial transplants in mice been have shown to cause changes in motor activity and anxiety. (14),(15)

11. Depression

Studies showed that gut bacteria could activate the immune and central nervous systems. It is believed that gut microorganisms are capable of producing and delivering neuro-active substances into the bloodstream. Studies on the impact of gut bacteria on mental health has only just begun.

Specifically, depression has been associated with elevated levels of lipopolysaccharide (LPS), an inflammatory toxin produced by bacteria in the gut. Similarly, bacteria have also been associated with the production of serotonin and gamma-aminobutyric acid, two compounds that affect the central nervous system and which are also linked to depression.

These findings have led to the term ‘psychobiotics’ to describe the use of probiotics for psychological treatments. Indeed, clinical psychiatry in the future may involve manipulation of the balance of our intestinal flora for the treatment of certain conditions such as depression. Research so far in rodents has suggested that certain probiotics may have antidepressant and anxiolytic activities. (16)

12. Schizophrenia

Current studies of patients support the finding that gut dysfunction may be the driving force for the onset of schizophrenia. Research has found links between the schizophrenia and bowel inflammation, food intolerances and Toxoplasma gondii gut parasite. All of these conditions are linked to a gut flora imbalance. (17),(18)

13. Alzheimers disease 

Alzheimer’s disease is the most common form of dementia in the western world. Currently, there is no known cure. There is plenty of experimental and clinical evidence linking gut bacteria to a number of brain and neurological disorders, but until recently,  the impact of gut bacteria on Alzheimer’s was unknown.

Researchers have now found that the gut bacteria of mice suffering from Alzheimer’s are different to a healthy control group without the disease. What’s more, mice with sterile guts had significantly less beta-amyloid plaque in the brain, which are the lumps that form on nerve fibers in patients with Alzheimer’s.

The study suggests now a direct link between the disease and gut bacteria composition. (19)

14. Parkinson’s Disease

Doctors have suspected for a long time that problems associated with Parkinson’s are always preceded by digestive system problems such as indigestion and bloating. In most cases, these symptoms show up years before Parkinson’s starts to affect their motor skills.

To prove this claim, scientists transferred fecal matter from humans with Parkinson’s into mice with the mouse model of the disease and found that the mice suffered further loss of motor function. Mice that received fecal transplants from healthy humans stayed the same.

The scientists believe that the gut bacteria could be secreting chemicals that over stimulates parts of the brain, leading to damage.  (20)

15. Cancer

A wide range of evidence now supports a role for gut microbes and the development of cancers. Research has been focussed on finding particular ‘smoking gun’ bacteria that are thought to cause cancer. But now, it thought that disturbance in gut bacteria could cause cancer through more indirect routes.

It is thought that changes in gut bacteria change the ability of what the gut can and cannot digest. As a result,  the gut may digest previously inaccessible nutrients, or it may also start metabolizing carcinogens which were previously left undigested.

Similarly, changes in gut bacteria change how the gut wall is regenerated, allowing potential carcinogens and toxins into the bloodstream. (21)

16. Arthritis

Rheumatoid arthritis is an autoimmune disease and chronic inflammatory disorder. Sufferers feel pain, swelling, loss of function and stiffness in joints. It is caused by the bodies own immune system attacking the membranes that line the joints.

Research has found differences in gut bacteria composition between sufferers and healthy patients. In particular, a microbe called Collinsella was over-represented in arthritic patients. As yet the mechanism by which this microbe stimulates an autoimmune response is as yet unknown. (22),(23)

17 Lupus

Lupus is a chronic autoimmune disease. The immune system becomes over-active and begins to attack healthy tissues, resulting in inflammation and swelling as well damage to kidneys, blood, heart, lung, and skin. Lupus is nine times more common in women than it is in men.

Again research is now suggesting that an intestinal flora imbalance could be playing an important role in its onset. Research conducted on mice have shown that the introduction of the bacteria Lactobacillus, a species common in yogurt, alleviated the symptoms of Lupus. Similarly, the introduction of a bacteria called Lachnospiraceae aggravated the symptoms. As a home remedy for lupus, yogurt seems to be a winner.

They also found different combinations of these bacteria between female and male mice.  If these differences are similar in human subjects, gut bacteria composition would explain the prevalence for women to contract the disease. (24)(25)

18 Multiple Sclerosis

Multiple Sclerosis is also an autoimmune disease where the immune system attacks the nervous system. However, there is still some debate as to whether it is an autoimmune disease, as the protein that the immune system is mistakenly attacking has not yet been identified.

As the disease attacks the nervous system, the symptoms are chronic and acute such as difficulty speaking, numbness, poor muscle coordination, and fatigue to name a few.

According to the “hygiene hypothesis”, it is thought that reduced exposure to infections, increased use of antibiotics as well as sterile home environments in childhood, may increase the risk of allergic and autoimmune diseases. (26),(27)

As with other autoimmune diseases, recent research is starting to point the finger at a link to gut bacteria. While the link between MS and gut bacteria is yet unproven, gut bacteria composition has been shown to be different between sufferers and healthy subjects and again a gut flora imbalance is a suspected cause of the disease. (28)

19 Liver disease

Non-alcoholic fatty liver disease describes several conditions where there is a build-up of fat in the liver. It is most common in patients that are obese. Healthy livers contain little or not fat, and while a small amount of fat in the liver is harmless, if it is allowed to build, it can lead to more complicated conditions such as diabetes, strokes and heart attacks.

Recent research has shown a link between the build-up of certain pathogenic bacteria in the small intestine and liver disease.  Non-alcoholic liver disease has been linked with an increase in pathogenic bacteria within the small intestines.

Likewise, patients with liver disease were much more likely to suffer from leaky gut walls (another symptom of unbalanced gut bacteria), further pointing the finger at a gut flora imbalance as a potential cause of liver problems (29)(30)

Do’s and Don’ts of Gut Flora


  • Regular exercise promotes the biodiversity of your gut flora. (31)(32)
  • Eat lots of fiber which is the main food source that healthy bacteria prefers.
  • Sleep more. Lack of sleep significantly damages your gut flora. (33)
  • Eat fermented food. Probiotics seed your gut bacteria and should be the cornerstone of any diet
  • Also remember to include prebiotics in your diet, – food for your good bacteria.
  • Do not over clean and sterilize.
  • Eat food rich in polyphenols. (34)
  • Always breastfeed if possible to seed your infant’s gut bacteria
  • Vaginal birth promotes the natural seeding of gut flora. If delivering by c-section, swab your baby with vaginal secretions at birth.


  • Use antibiotics unless absolutely necessary
  • Eat excessive amounts of red meat which can cause overgrowth of Bilophila bacteria linked to inflammation (35)
  • Use artificial sweeteners as they upset the balance of your gut bacteria (36)
  • Over clean and sterilize everything. A little uncleanliness is good.


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