London, June 22 (IANS) Drinking four cups of coffee a day helps protect against oral cancer, but doctors are of the opinion that people should drink coffee in moderation because the caffeine present in it can increase heart rate and blood pressure.

Some of the 1,000 chemicals present in coffee - including antioxidants - can offer protection against many types of cancer, a new research has said.

The research, comprised of nine studies conducted in Europe, America and Central America, compared the coffee habits of around 5,000 cancer patients and more than 9,000 healthy people, and took into account their smoking, diet and alcohol habits.

The researchers found that regular coffee drinkers were 39 percent less likely to develop cancers of the mouth and pharynx than people who drank no coffee.

"We had a very large sample size, and since we combined data across many studies, we had more statistical power to detect associations between cancer and coffee," Mia Hashibe, the study's lead author from the University of Utah in Salt Lake City, was quoted as saying by the Daily Mail.

Around 5,500 Britons are diagnosed each year with cancer of the lips, tongue, tonsils, gum and other parts of the mouth, while 1,800 of them die from the disease.

Studies on the links between coffee and cancer have produced confusing and sometimes contradictory results. These results confuse because coffee drinking could be a marker for some other lifestyle factors that increase cancer risk, such as smoking and alcohol.

The study was published in Cancer Epidemiology, Biomarkers and Prevention, a journal of the American Association for Cancer Research.