The nut of the betel or areca palm tree contains a mild, central nervous system stimulant called arecoline. Chewing the nut on its own or with a mixture of tobacco, lime and betel leaf is a popular habit in Asian countries and among British Asians.

While all betel chewers have an increased chance of developing mouth cancer, scientists believe the genetic make-up of a person is likely to influence their susceptibility to the disease.

Researchers based in Taiwan looked at variations in a gene that protects cells from damage in male betel chewers. They found that men with mouth cancer often had a different version of a gene than those not affected by the disease.

Their findings shed important light on how mouth cancer develops and why some men are more susceptible to the disease than others.

Over 153,000 new cases of mouth cancer are diagnosed in Asia each year. It accounts for up to 50 per cent of malignant tumours in some South Asian countries due to the popularity of betel chewing.

Researchers based at the National Yang-Ming University in Taiwan looked at variations of a gene called HO-1(2). The gene helps protect cells from damage by harmful agents such as UV irradiation or hydrogen peroxide.

But studies also suggest that the gene may be involved in promoting tumour growth and maintaining cancer cell survival.

Scientists think that certain versions of the gene may help prevent disease while other versions may trigger disease.

Lead researcher Dr Shu-Chun Lin says: "We know that chewing betel nut increases a person risk of mouth cancer. But not everyone who takes up the habit develops mouth cancer so there must be genetic factors involved.

"Particular variations of the gene have been associated with an increased risk of heart or lung disease. This is the first study to look at whether different forms of the gene affect mouth cancer risk."

The team looked at variations of the HO-1 gene in 147 male betel chewers with mouth cancer, 71 with oral submucous fibrosis (a scarring condition of the oral cavity) and 83 control subjects who did not have mouth cancer.

They found that one variation of the gene was much more common in men with mouth cancer when compared to men who did not have any signs of the disease.

It was also identified in high frequencies in men with the most common type of mouth cancer - buccal squamous cell carcinoma.

Dr Shu-Chun Lin says: "Our study shows that men with a particular version of the HO-1 gene have a two-fold increased risk of developing mouth cancer."

Dr Lesley Walker, Director of Cancer Information at Cancer Research UK, says: "We know that betel chewers run the risk of getting mouth cancer. This report suggests that if people chew betel and also possess this particular gene variant “ their risk of the disease is even higher.

"Most cases of cancer are caused by a combination of genetic and environmental factors. It's important to remember that habit and lifestyle can have a big effect on the risk of mouth cancer. The best way to prevent the betel-related mouth cancer is to avoid chewing the nut on its own or in combination with tobacco."

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Click here to read an interesting Betelnut chewing anecdote