Functions of the gut and oral biome 

The mouth is second only to your gut as the largest and most diverse microbiome in your body(1). The mouth is the beginning of your gut microbiome, and all nutrients pass through it on their way to your gut. Both biomes act as key interfaces between our bodies and the environment, keeping our insides safe from outside intruders.  

Consuming everyday foods, for example, also introduces a host of microorganisms into our bodies; some of them are friendly whereas others are not. Unwanted attempts to dominate the oral cavity from harmful bacteria (such as Streptococcus mutans and Treponema denticola) are often thwarted by our first line of defence - the oral flora. According to Dr. Floyd Dewhirst, a dental expert who studies microbes at the Forsyth Institute, species work together to support other members of their community; buffering an environment that favours their survival(2). How exactly these mechanisms work is under current scientific investigation.  

Sometimes healthy communities are overwhelmed by external factors. The gut is constantly faced with complex chemical food additives like sugar alcohols, emulsifiers, food colourants, flavour enhancers, thickeners, anticaking agents, and preservatives that present a risk to our native biomes. Artificial sweeteners, for instance, Saccharine (E954), Sucralose (E955), and Aspartame (E951) have been found to increase the number of Bacteroides spp. and Clostridiales phylum in the intestine creating weight gain in rats. High volumes of these harmful species have been proven to cause liver inflammation in mice(3)

The bidirectional effect of the oral and gut biome  

In many cases of gut dysfunction disorders (irritable bowel disease, Crohn’s disease, and ulcerative colitis) patients often present oral signs. If you have particular concerns, you may choose to discuss them further with your local holistic dentist. For general indicators of gut inflammation please check your mouth for the following: 

• A red or swollen tongue may indicate a lack of folic acid and vitamin B complex.  
• Sore, flat, red patches on the gums and inside of cheeks can be a sign of vitamin B12 deficiency. 
• Oral candida or yeast infection may signal zinc deficiency due to poor digestive function and immune imbalance. 
• Mouth ulcers or inflamed gums can indicate digestive problems. 
• White pus-filled lesions are also seen in the colons of Crohn’s disease patients. 
• Burning mouth syndrome may also include a loss of taste, dry mouth and oral inflammation. This can suggest mineral and low vitamin levels. However, it may also be a side effect of medications such as anti-depressants(4)

Severe oral disease can impact the whole body through the translocation of harmful species. Bacteria can seep into the blood circulatory system through tiny blood capillaries in the mouth, infecting sensitive organs. Ingested unbalanced saliva can also carry a plethora of oral bacteria to the intestine, where it has been shown to negatively impact the microbiota community and reduce immune defence(5). Once these pathogens become the dominating species, they wreak havoc in the gut microbiome and body, causing further inflammation and organ dysfunction. 

Supporting the oral x gut connection 

Dr Hisham’s Dental Care System is a nutritionally active, dentist-designed range to specifically nurture and support a healthy oral biome. As the mouth seeds and feeds the gut biome, it is important to introduce beneficial foodstuffs to the body. When brushing with Dr Hisham’s teeth serum, for example, you would brush, spit but not rinse. The advanced prebiotics are best kept in the mouth to further suppress bad bacteria and nurture beneficial bacteria in your oral microbiome. 


Our bodies are natural hosts for the hugely diverse world of microbiomes. Although our oral and gut biomes are located in different regions, they both serve as an interface between our body and the wider environment. To the holistic eye, gut disfunction can be seen in the mouth in the form of ulcers, sores, or swollen tongues. On the other hand, an unhealthy mouth can fester and become a source of contamination leaking out and causing systemic disease. Seeding and feeding the gut biome starts with the mouth, so implementing a holistic dental care system, like Dr Hisham’s, is a surefire way to strengthen both biomes and find healthful balance.