Microbes refer to bacteria, viruses, fungi and other microorganisms existing inside the human body. Trillions of these occupy the inside of the intestines and on the skin. Gut microbiome is the medical term for the microbes that are found in a certain part of the large intestine known as the cecum.

There are up to 1000 species of bacteria in an individual’s gut microbiome. Bacterial cells in the body outnumber human cells by around 10 trillion. While most species are beneficial to our health, certain species are the cause of diseases.

Together, these microbes make up the gut microbiome, which plays an important role in human health. This post examines excessive consumption of sugar or high sugar levels and how it affects this important part of the digestive system.

Too much sugar may block the production of a protein associated with leanness

In a study funded by Yale University and the National Institutes of Health, it was found that high consumption of sucrose and fructose (two different forms of simple sugars) could be affecting the composition of the gut microbiome.

In fact, a study conducted on mice found that a high sucrose/glucose diet affected a beneficial type of bacteria, the Bacteroides thetaiotaomicron. This species is associated with an individual’s ability to process certain healthy food items, like vegetables. Sucrose (or table sugar) is formed of both fructose and glucose and has been found to block the production of Roc, a protein required for the colonisation of this specific type of bacteria in the gut.

When researchers in the study engineered a strain of this bacterium that didn’t prevent the production of Roc, this strain didn’t prevent the protein from colonising it. This allowed for healthier gut microbiome.

Researchers concluded that the role of the diet in the gut microbiota lies beyond just providing nutrients. Carbohydrates like sugar can even act as a signalling molecule.

Diets high in sugar can cause inflammation in the body

A diet that’s high in processed food and added sugar can eliminate the beneficial bacteria in the human gut. The resulting imbalance can cause increased cravings for sugar, which further damage the gut.

An unhealthy amount of unrefined sugar, especially high-fructose corn syrup, leads to inflammation in the body. This itself can lead to additional diseases including certain types of cancer.

Increased vulnerability of high blood sugar and diabetes

Another drawback of high levels of sugar is that it affects the ability of the gut microbiome to regulate blood sugar. This directly affects the possible onset of Type 1 and 2 diabetes.

A recent study examined 33 infants who, genetically, had a high risk of developing Type 1 diabetes. It was found that the diversity of microbiome dropped abruptly prior to the onset of type 1 diabetes.

Additionally, researchers also demonstrated noticeable levels of unhealthy bacteria species prior to the diagnosis of this condition.

A separate study found that even when people eat the exact same food, their blood sugar spikes in different ways. This is believed to be due to the types of bacteria found in the gut microbiome.

Too much sugar can reduce beneficial bacteria leading to a leaky gut syndrome

An increase of pathogenic bacteria, which is the species of microorganisms that cause diseases, can lead to a condition known as dysbiosis. An increase of this type of bacteria causes changes to the internal mucosal barrier of the intestine.

With the reduction of beneficial bacteria along this barrier, its permeability is altered, allowing harmful substances to pass through. This then leads to leaky gut syndrome, which launches an inflammatory immune response targeting the substance that leaks through the intestines of the wall.


What does sugar do to gut bacteria? 

The effect of sugar on gut bacteria varies based on the type of bacteria involved. The gut microbiome is home to many kinds of bacteria and may not react to sugar the same way.


Bacteria, however, need energy, and sugar can be broken down to provide this energy for the bacteria’s growth. When a person has a high sugar diet, some of these sugars make their way into the gut microbiome, and this gives some bacteria the energy to multiply, throwing off the balance in the microbiome.

Maintaining a balanced diet is crucial to the health of an individual’s gut microbiome

As demonstrated above, individuals need to be wary about incorporating too much sugar into their daily diets. Excessive sugar has a negative impact on the gut microbiome and can lead to serious health conditions if caution is not taken.

How long does it take to improve the gut microbiome?


Depending on how extensive the effect of sugar on gut bacteria was, the gut microbiome could take some time to improve.


 That being said, the average time it takes to build up a healthy gut microbiome is about 6 months.

By following a balanced diet, individuals can expect to lead healthy lives. For patients who are concerned about their health, they can
receive guidance and professional medical advice from Dr Suirdan Vivekanandarajah, a leading interventional gastroenterologist and hepatologist based in Sydney.

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