Dentist names the bowel cancer warning signs that appear in your mouth: ‘Don’t ignore bleeding gums, bad breath and a slimy white tongue’

In the UK, someone is diagnosed with bowel cancer every 12 minutes and around 17,000 people die from it each year. 

Also called colorectal cancer, it is the second most common cause of cancer death in Britain.

While changes in bowel habits and stomach discomfort are the most well-known warning signs, research suggests that changes in the mouth may also be linked to bowel cancer risk.

Dr Mark Burhenne, known online as The Sleep Dentist, warns that common dental problems could indicate an imbalance in the oral microbiome – the ‘good’ bacteria in your mouth. 

When harmful bacteria dominate the oral microbiome, studies suggest this may be associated with an increased risk of bowel cancer.

Some harmful bacteria from the mouth can reach the gut, where research suggests they may contribute to inflammation that could promote cancer growth in certain cases. 

Poor brushing and flossing, smoking, too much alcohol, and a high-sugar, low-fibre diet can all upset this delicate ecosystem. 

A study published in the International Journal of Cancer found that women with fewer teeth or gum disease have a slightly higher risk of bowel cancer, especially in the upper parts of the colon. 

Dr Burhenne says some common dental problems may signal changes in mouth bacteria that could be connected to a higher risk of colon cancer.

Bleeding, puffy or receding gums

Many people are aware that spitting blood when you brush your teeth could be a sign of gum disease. However, research suggests that gum disease may be associated with changes in gut health, though it is not a direct warning sign of bowel cancer.

Bleeding gums are a primary symptom of gingivitis and periodontitis, progressive stages of gum disease caused by plaque buildup.

When gums bleed during brushing, it indicates an active infection and inflammation, allowing harmful oral bacteria to enter the bloodstream and be swallowed into the digestive system.  

Dr Burhenne notes that Harvard researchers found that people with periodontal disease have a 17 to 21 per cent higher risk of precancerous colon polyps. 

‘The bleeding isn’t just a symptom. It’s the mechanism,’ he adds. 

As well as this, puffy, tender gums without visible bleeding can signal early gingival inflammation, according to Dr Burhenne.

‘This is almost entirely asymptomatic, which is exactly why it goes unaddressed for years,’ he adds.

Bad breath

Persistent bad breath may be linked to Fusobacterium nucleatum, a bacterium found in the mouth that is also associated with gum disease and has been observed in some bowel cancer tumours.

Fusobacterium nucleatum has been identified in high concentrations within bowel cancer tumours. 

It is believed that the bacteria can travel via saliva or blood cells to other parts of the body, potentially aiding cancer growth by shielding cells from immune system attacks.

White or yellow tongue

A white or yellow coating on the tongue is usually caused by bacteria, debris, or dead cells accumulating, often due to poor oral hygiene, dehydration or dry mouth. 

Some research has suggested that certain tongue coatings may reflect changes in the oral microbiome, which could be linked to bowel cancer risk.

‘That coating is like a bacteria reservoir,’ writes Dr Burhenne. ‘You swallow a litre of saliva every day – everything on your tongue goes with it.’ 

Losing four or more teeth

People who have lost four or more teeth, often due to decades of untreated periodontal disease, have a 20 per cent higher risk of precancerous colon polyps, according to Harvard and AACR data. 

Even losing a few teeth may be associated with a higher risk of precancerous colon growths, according to research. 

While dental problems alone are not a definite warning sign, maintaining a healthy oral microbiome and taking part in regular screening could be life-saving.

Experts stress that good oral hygiene – brushing, flossing, and regular dental check-ups – is essential but the most effective protection against bowel cancer remains early detection. 

The NHS bowel cancer screening programme can detect tiny traces of blood in the stool before symptoms appear. A healthy diet, exercise, and avoiding smoking or heavy drinking also play a key role.