Poor oral health is associated with a 75 per cent increased risk of hepatocellular carcinoma (HCC), the most common form of liver cancer, a study has found.
Researchers at Queen's University Belfast analysed a large cohort of over 469,000 people in the UK.
They investigated the association between oral health conditions and the risk of a number of gastrointestinal cancers, including liver, colon, rectum and pancreatic cancer.
Models were applied to estimate the relationship between cancer risk and self-reported oral health conditions, such as painful or bleeding gums, mouth ulcers and loose teeth.
While no significant associations were observed on the risk of the majority gastrointestinal cancers and poor oral health, a substantial link was found for hepatobiliary cancer.
"Poor oral health has been associated with the risk of several chronic diseases, such as heart disease, stroke and diabetes," said Haydee WT Jordao, from the Queen's University Belfast.
"However, there is inconsistent evidence on the association between poor oral health and specific types of gastrointestinal cancers, which is what our research aimed to examine," said Jordao, lead author of the study published in United European Gastroenterology Journal.
Of the 469,628 participants, 4,069 developed gastrointestinal cancer during the (average) six-year follow up.
In 13 per cent of these cases, patients reported poor oral health.
Participants with poor oral health were more likely to be younger, female, living in deprived socioeconomic areas and consumed less than two portions of fruit and vegetables per day.
The biological mechanisms by which poor oral health may be more strongly associated with liver cancer, rather than other digestive cancers, is currently uncertain.
One explanation is the potential role of the oral and gut microbiome in disease development.
"The liver contributes to the elimination of bacteria from the human body," said Jordao.
When the liver is affected by diseases, such as hepatitis, cirrhosis or cancer, its function will decline and bacteria will survive for longer and therefore have the potential to cause more harm.
"One bacteria, Fusobacterium nucleatum, originates in the oral cavity but its role in liver cancer is unclear. Further studies investigating the microbiome and liver cancer are therefore warranted," said Jordao.
Another theory explaining the higher cancer risk due to poor oral health suggests that participants with a high number of missing teeth may alter their diet, consuming softer and potentially less nutritious foods, which in turn influence the risk of liver cancer.