Betel - Health Effects

Health Effects

The betel leaf is predominantly consumed as betel quid or paan, which is a mixture of substances. The paan almost always contains a betel leaf with two basic ingredients, either areca nut or tobacco or both, with lime (calcium hydroxide or calcium carbonate). When areca nut is consumed with tobacco it is considered as carcinogenic.

In an extensive scientific research monograph, the World Health Organization expert group for research on cancer reported in 2004 that the percentage of oral cancer among all cancers diagnosed in hospitals in Asia has always been much higher than that usually found in western countries, where the habit of chewing betel quid, with or without tobacco, is virtually unknown. In many descriptive studies, investigators have obtained histories of chewing betel quid with tobacco from series of patients with oral cancer; and in all these studies the percentage of patients who practice betel leaf chewing was found to be extremely large. Researchers also noted that the cancer generally develops at the place where the betel quid is kept.

In an earlier ca. 1985 study, scientists linked malignant tumors to the site of skin or subcutaneous administration of aqueous extracts of betel quid in mice. In hamsters, forestomach carcinomas occurred after painting of the cheek-pouch mucosa with aqueous extracts or implantation of a wax pellet containing powdered betel quid with tobacco into the cheek pouch; carcinomas occurred in the cheek pouch following implantation of the wax pellets. In human populations, they report observing elevated frequencies of micronucleated cells in buccal mucosa of people who chew betel quid in Philippines and India. The scientists also found that the proportion of micronucleated exfoliated cells is related to the site within the oral cavity where the betel quid is kept habitually and to the number of betel quids chewed per day. This proportion, they report, could be reduced by administration for two to three months of vitamin A or β-carotene or a mixture of the two. In related studies, the scientists reported that oral leukoplakia shows a strong association with habits of betel-quid chewing in India. Some follow-up studies have shown malignant transformation of a proportion of leukoplakias. Oral submucous fibrosis and lichen planus, which are generally accepted to be precancerous conditions, appear to be related to the habit of chewing betel quid, that is paan.

In a study conducted in Papua New Guinea, scientists found oral squamous cell cancer as the most common malignant tumour in Papua New Guinea. They report that the oral cancer is concentrated at the corner of the mouth and cheek, and corresponds precisely with chewing site of betel leaf with lime in 77% of 169 cases. Powdered slaked lime applied to the chewed areca nut placed inside a betel leaf causes the mean pH to rise to 10, at which reactive oxygen species are generated from betel quid ingredients in vitro. Reactive oxygen species, together with sustained lime-induced cell proliferation, the scientists claim suggest a possible mechanism of carcinogenesis for this tumor.

In a study conducted in Taiwan, scientists found betel chewing increases the risk of cardiovascular disease and mortality. In this study, they investigated the association between betel nut chewing and general obesity (BMI 25 kg/m2) and central obesity. Using multiple linear regression analyses, after adjusting for potential confounders, they claim betel consumption was statistically significantly associated with obesity. The reason for this link between obesity and betel leaf chewing, the scientists admit is unclear.

In another study, scientists report the extent of cancer risks of betel quid chewing (without tobacco added) beyond oral cancer. In addition to oral cancer, significant increases were seen among chewers for cancer of the esophagus, liver, pancreas, larynx, lung, and all cancer. Chewing and smoking, as combined by most betel chewers, interacted synergistically and was responsible for half of all cancer deaths in this group. Chewing betel leaf quid and smoking, the scientists claim shortened the life span by nearly 6 years.

A Lancet Oncology publication claims that betel leaf quid, or paan masala, may cause tumours in different parts of the body and not just the oral cavity as previously thought.

In a study conducted in Sri Lanka, scientists found high prevalence of oral potentially malignant disorders in rural Sri Lankan populations. After screening for various causes, the scientists report betel-quid chewing being the major risk factor, with or without tobacco.

In October, 2009, 30 scientists from 10 countries met at the International Agency for Research on Cancer (IARC), a World Health Organization sponsored group, to reassess the carcinogenicity of various agents including betel leaf quid with areca nut, and mechanisms of carcinogenesis. They concluded there is sufficient evidence that betel quid without tobacco leads to tumor in oral cavity and oesophagus, and that betel quid with added tobacco is a carcinogen to oral cavity, pharynx and oesophagus.

The high rate of oral cancer in South Asia is thought to be due to the chewing of betel preparations; the inclusion of tobacco may worsen the risk, but there is also evidence that the areca nut, alone or as part of a betel quid, may cause cancer even without tobacco. See its article for more discussion of this point.

Some scarce reports may suggest that betel leaf by itself has adverse health effects. For example, one research paper studied chromosome damaging effect of betel leaf in human leukocyte cultures. These researchers report an increase in the frequency of chromatid aberrations when the leaf extract was added to cultures. Another scientific study from Japan indicates that the lab rats who ate a mixture of betel leaf and areca nuts all had severe thickening of the upper digestive tract whereas after undergoing a diet of betel leaves alone, only one laboratory rat ended up having a forestomach papilloma .

Scientific studies that evaluate the health effects of betel leaves by itself are however limited, in contrast to extensive medical studies on betel quid or paan, which always includes betel leaf with additional substances such as those discussed above. No negative reports have been made of preparations based on betel leaves that do not contain areca nut, tobacco nor (mineral) lime, that are not chewed like paan but eaten whole, such as miang kham, a thai snack wrapped in wild betel leaves, containing a mixture of spices, dried shrimp, cooked meat, chili, fruit bits and roast nuts, served with a sauce composed of fish sauce and palm syrup. Other vine leaves related to betel in the genus Piper are also used fresh as wrapping medium which are eaten with their stuffing, such as vietnamese meat preparations wrapped in "Lolot" leaves and no adverse effects have been observed.