People with a history of periodontal (gum) disease appear to have a higher risk of developing mouth and stomach cancer, warn researchers.Periodontitis or gum disease is a serious gum infection that damages the soft tissue and, without treatment, can destroy the bone that supports your teeth.Periodontitis can cause teeth to loosen or lead to tooth loss.The study, published in the journal Gut, found that a history gum appeared to be associated with a raised risk of oesophageal (gullet) cancer and gastric (stomach) cancer and this risk were also higher among people who had lost teeth previously."Previous findings on the relationship of periodontal disease and tooth loss with oesophageal and gastric cancer have been inconsistent," said the study researchers from the Harvard University in the US.For the current results, the research team examined the association of history of periodontal disease and tooth loss with the risk of oesophageal and gastric cancer in 98,459 women (1992-2014) and 49,685 men (1988-2016).Dental measures, demographics, lifestyle, and diet were assessed using follow-up questionnaires and self-reported cancer diagnosis was confirmed after reviewing medical records.The results showed that during 22-28 years of follow-up, there were 199 cases of oesophageal cancer and 238 cases of gastric cancer.A history of periodontal disease was associated with a 43 per cent and 52 per cent increased risk of oesophageal cancer and gastric cancer, respectively. Compared to people with no tooth loss, the risks of oesophageal and gastric cancer for those who lost two or more teeth were also modestly higher - 42 per cent and 33 per cent, respectively.In addition, among individuals with a history of periodontal disease, no tooth loss and losing one or more teeth were equally associated with a 59 per cent increased risk of oesophageal cancer.Similarly, the same group of individuals had 50 per cent and 68 per cent greater risk of gastric cancer, respectively."Together, these data support the importance of the oral microbiome in oesophageal and gastric cancer," the study authors wrote."Further prospective studies that directly assess oral microbiome are warranted to identify specific oral bacteria responsible for this relationship," they concluded.