According to Henry James, “There are few hours in life more agreeable than the hour dedicated to the ceremony known as afternoon tea.”
He may not have been thinking of oral cancer prevention when he wrote that, but it might be one more reason (as if any were needed) to have a daily cup.
Tea contains polyphenols that, in laboratory and clinical studies, have shown to have protective effects against lung, esophageal, and other cancers. Although numerous studies have examined the relationship between tea consumption and the risk of oral cancer, the results have been inconsistent—some have found a significant risk reduction from drinking tea while others have found no effect.
To determine whether drinking tea might keep mouths healthy, researchers in Qingdao, China, carried out a meta-analysis of 19 prospective and case-control studies of tea drinking and oral cancer conducted worldwide.1 Taken together, the studies included 4,675 oral cancer cases. Four of the studies found a protective effect of tea drinking against oral cancer whereas the remaining 15 did not.
The authors of the meta-analysis pooled the data from all 19 studies and looked at the risk of cancer according to the level of tea consumption, and found positive results. Subjects who drank the most tea of any type had a 15% reduction in the risk of oral cancer compared with subjects who drank the least (relative risk [RR] = 0.853; 95% CI: 0.779-0.934).
However, not all tea is created equal. In five of the studies, the focus of research was green tea; and in three studies, it was black. Those who drank the most green tea had a significantly reduced risk of oral cancer compared with those who drank the least (RR = 0.798; 95% CI: 0.673-0.947), whereas black tea showed no such effect (RR = 0.953; 95% CI: 0.792-1.146).
The Big Picture
If drinking tea really does help prevent oral cancer, tea-drinking countries ought to have lower rates of the disease. In the United Kingdom, where mean annual tea consumption is 2.74 kg per person, the incidence of oral cancer is 10.4 per 100,000, about 25% lower than in the United States, where we drink a mere 0.33 kg of tea per person.2-4 Smoking and alcohol consumption are important risk factors for oral cancer, but in this case they seem to even out: the British smoke less than Americans but drink more—13.37 L of pure alcohol per person per year in the United Kingdom compared with 9.44 L in the United States.5,6
The highest tea-consuming country in the world is Turkey, where they drink a whopping 6.87 kg of tea per person each year.2 Perhaps partly as a result, they enjoy a low rate of oral cancer—just 4.4 cases per 100,000.7 Contributing further to the low rate of oral cancer in Turkey may be the low rate of alcohol consumption—2.87 L per person per year.6
Tea consumption in China is just 0.82 kg per person annually, but most of that is green tea, which may be the reason why oral cancer is relatively infrequent there—3.3 cases per 100,000 annually.1
Of course, epidemiologic associations don’t prove causation, but they’re interesting to contemplate over a nice cup of tea. As the 19th century British writer Sydney Smith said, “I am glad I was not born before tea.”
- Wang W, Yang Y, Zhang W, Wu W. Association of tea consumption and the risk of oral cancer: a meta-analysis. Oral Oncol. 2014 Jan 2. [Epub ahead of print]
- Food and Agriculture Organization of the United Nations. Data tables. http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID=567#ancor. Accessed February 7, 2014.
- ral/incidence/uk-oral-cancer-incidence-statistics. Accessed February 7, 2014.
- National Cancer Institute. Oral cancer. http://www.cancer.gov/cancertopics/types/oral. Accessed February 7, 2014.
- TobaccoAtlas.org. World tables. http://tobaccoatlas.org/uploads/Images/PDFs/TA4_pdf_world_tables.pdf. Accessed February 7, 2014.
- World Health Organization. Global status report on alcohol and health. Geneva, Switzerland: WHO Press; 2011.
- de Carmago Cancela M, Voti L, Guerra-Yi M, et al. Oral cavity cancer in developed and in developing countries: population-based incidence. Head Neck. 2010;32(3):357-367.