The betel (Piper betle) is the leaf of a vine belonging to the Piperaceae family, which includes pepper and kava. It is valued both as a mild stimulant and for its medicinal properties. Betel leaf is mostly consumed in Asia, and elsewhere in the world by some Asian emigrants, as betel quid or in paan, with or without tobacco, in an addictive psycho-stimulating and euphoria-inducing formulation with adverse health effects. Betel is notable for staining the teeth of regular users.
In Sri Lanka and in the Indian states of Karnataka, Kerala, Tamil Nadu, Andhra Pradesh and West Bengal a sheaf of betel leaves is traditionally offered as a mark of respect and auspicious beginnings. Occasions include, greeting elders at wedding ceremonies, New Year, offering payment to Ayurvedic physicians and astrologers where usually money and or areca nut are kept on top of the sheaf of leaves and offered to the elders for their blessings.
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The betel leaf is cultivated mostly in South and Southeast Asia, from Pakistan to Papua New Guinea. It needs a compatible tree or a long pole for support. Betel requires well-drained fertile soil. Waterlogged, saline and alkali soils are unsuitable for its cultivation.
In Bangladesh, farmers called barui prepare a garden called a barouj in which to grow betel. The barouj is fenced with bamboo sticks and coconut leaves. The soil is plowed into furrows of 10 to 15 metres' length, 75 centimetres in width and 75 centimetres' depth. Oil cakes, manure, and leaves are thoroughly incorporated with the topsoil of the furrows and wood ash. The cuttings are planted at the beginning of the monsoon season.
Proper shade and irrigation are essential for the successful cultivation of this crop. Betel needs constantly moist soil, but there should not be excessive moisture. Irrigation is frequent and light, and standing water should not remain for more than half an hour.
Dried leaves and wood ash are applied to the furrows at fortnightly intervals and cow dung slurry is sprinkled. Application of different kinds of leaves at monthly intervals is believed advantageous for the growth of the betel. In 3 to 6 months the vines reach 150 to 180 centimeters in height and they will branch. Harvest begins, with the farmer plucking the leaf and its petiole with his right thumb. The harvest lasts 15 days to one month. Betel plant has made its way to research labs of many Bangladesh chemical and food nutrition companies.
The harvested leaves are consumed locally and exported to other parts of Asia, the Middle East, Europe, and the Americas. Betel is grown and cultivated as an important crop in rural Bangladesh.
An extensive ca. 2004 research monograph by the World Health Organization, reports that betel leaf is consumed, in southeast Asian community worldwide, predominantly as a betel quid (synonymous with pan or paan). The betel quid contains betel leaf, areca nut and slaked lime, and may contain tobacco.
Arecoline is the primary active ingredient responsible for the central nervous system effects of the areca nut. Arecoline has been compared to nicotine; however, nicotine acts primarily on the nicotinic acetylcholine receptor. Arecoline is known to be a partial agonist of muscarinic acetylcholine M1, M2, M3 receptors and M4, which is believed to be the primary cause of its parasympathetic effects (such as pupillary constriction, bronchial constriction, etc.). LD50: 100 mg/kg, administered subcutaneously in mouse.
Other substances are often added to the betel quid, in particular spices, such as cardamom, saffron, cloves, aniseed, turmeric, mustard or sweeteners according to local preferences. Numerous commercially produced mixtures containing some or all of these ingredients are also available in various parts of the world. The betel quid is thus a mixture of substances, placed in the mouth; and betel leaf is not consumed alone. For a predominant majority, the paan usually contains the betel leaf with two basic ingredients, either tobacco or areca nut or both, in raw or any processed form.
The betel quid, or paan, as consumed in various parts of the world, consists of,:
The origin and diffusion of betel chewing remains a somewhat unresolved issue since there is little unequivocal evidence to support the very early dates often quoted. 
In Bangladesh, Myanmar, Indonesia, Thailand, India, Vietnam, Sri Lanka and other parts of South Asia and Southeast Asia, the leaves are chewed together in a wrapped package along with the areca nut (which, by association, is often inaccurately called the "betel nut") and mineral slaked lime (calcium hydroxide). Catechu, called Kattha in Hindi, and other flavoring substances and spices might be added. The lime acts to keep the active ingredient in its freebase or alkaline form, thus enabling it to enter the bloodstream via sublingual absorption. The areca nut contains the alkaloid arecoline, which promotes salivation (the saliva is stained red), and is itself a stimulant. This combination, known as a "betel quid", has been used for several thousand years. Tobacco is sometimes added.
In Bangladesh, Paan chewing has mostly subsided or decreased, as the post independence young generation have not picked up the habit from their peers. In the countryside it is prevalent among the elderly, but in cities, it is mostly chewed after dinner at a particular occasion.
The betel and areca play an important role in Indian culture, especially among Hindus. Many traditional ceremonies governing the lives of Hindus use betel and areca. For example, when paying money to a priest one might place money in a betel leaf. Even in North America and Europe, many Hindu peoples chew betel leaf and it is widely available in Indian grocery stores.
The betel and areca also play an important role in Vietnamese culture. In Vietnamese there is a saying that "the betel begins the conversation", referring to the practice of people chewing betel in formal occasions or "to break the ice" in awkward situations. The betel leaves and areca nuts are used ceremonially in traditional Vietnamese weddings. Per tradition a groom might offer the bride's parents betel and areca, the leaf and the nut symbolizing the ideal married couple bound together. In Vietnamese the phrase "matters of betel and areca" (chuyện trầu cau) is synonymous with marriage.
In Papua New Guinea, betel is prepared with a mustard stick dipped in lime powder, and acts as a stimulant to suppress hunger, reduce stress and heighten the senses. Most families have backyard gardens, and many grow betel there.
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). Areca nut is considered carcinogenic when consumed with or without tobacco.
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, suggests 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 reports may suggest that betel leaf by itself has adverse health effects, in part because of tannins delivered by the leaf and for reasons currently not fully understood. 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 that 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 teams from Taiwan, Malaysia and Papua New Guinea have reported that expectant mothers who chew betel quid, during pregnancy, significantly increase adverse outcomes for the baby. The effects of betel quid and areca nut were similar to those reported for mothers who consume alcohol or tobacco during pregnancy. Lower birth weights, reduced birth length and early term were found to be significantly higher.
Betel vines are cultivated throughout southeast Asia in plots whose area is typically 20 to 2000 square metres (0.005 to 0.5 acre).
Malaysian farmers cultivate four types of betel plants: sirih India, sirih Melayu, sirih Cina and sirih Udang. The harvest is then sold in bundles of 10 leaves, each bundle costing in 2011 between RM 0.30 to 0.50 ($0.10 to $0.15 per leaf).
In Sri Lanka, betel is grown all over the country but the commercial production of betel, with bigger leaves with dark green colour combined with thickness, known as “kalu bulath” is confined to a few districts such as Kurunagala, Gampaha, Kegalle, Kalutara and Colombo. These are sold at a whole seller lots of 1000 leaves. In a report published by the United Nations Food and Agriculture Organization (FAO), a successful betel farm in Sri Lanka can provide a supplemental income to a farmer by providing six days of work every six months and net income when the leaf prices are attractive. The FAO study found the successful farm’s yield to be 18,000 leaves per 150 square feet (14 m2). The additional salary and income to the Sri Lankan betel grower, assuming he or she provides all needed labor and keeps all net profit, to be SL Rs. 1635 per 150 square feet (14 m2) of betel farm every 6 months ($90 per "decimal" per year, or $9000 per acre per year). If the farmer hires outside labor to tend the betel vines, and harvest the crop, the FAO found the net income to the betel farm owner to be SL Rs. 735 per 150 square feet (14 m2) of betel farm every 6 months ($40 per decimal per year, or $4000 per acre per year). According to FAO, the market prices for betel leaves vary with wet and dry season in Sri Lanka, and in 2010 averaged SL Rs. 200-400 per 1000 leaves ($1.82 to $3.64 per 1000 leaves). The FAO study assumes no losses from erratic weather, and no losses during storage and transportation of perishable betel leaves. These losses are usually between 35% to 70%.
In Bangladesh, betel leaf farming yields vary by region and vine variety. In one region where betel leaf cultivation is the main source of income for farmers, a total of 2,825 hectares of land is dedicated to betel vine farming. The average production cost for these betel farms in Bangladesh are about Tk 300,000 per hectare ($4000 per hectare, $16 per decimal), and the farm owners can earn a profit of over Tk 100,000 per hectare ($1334 per hectare, $5.34 per decimal).
In India, a 2006 research reported betel vines being cultivated on about 55000 hectares of farmland, with an annual production worth of about IN Rs. 9000 million ($200 million total, averaging $1455 per acre). The betel farming industry, the report claims, supports about 400,000 - 500,000 agricultural families.
A March 2011 report claims that betel farming is on a decline in India. While in ideal conditions, some farms may gross annual incomes after expenses of over IN Rs. 26,000 per 10 decimal farm ($5,780 per acre), a betel farm income is highly erratic from year to year, because of rainfall patterns, temperature, and spoilage rates of 35% to 70% during transport over poor infrastructure. Simultaneously, the demand for betel leaves has been dropping in India because of contagious acceptance of gutkha (chewing tobacco) by consumers over betel leaf-based ‘‘paan’’ preparation; the report cites betel leaf trading has dropped by 65% from 2000 to 2010, and created an over supply. As a result, the report claims Indian farmers do not find betel farming lucrative anymore.
The betel leaf is known as Pan in Bengali and Paan in Hindi, Tambula and Nagavalli in Sanskrit, and Tanbul in Persian. Some of the names in the regions in which it is consumed are: Vetrilai (Tamil வெற்றிலை), (vettrilai - வெற்ற (vettri, "victory") + இலை (ilai, "leaf")),Tamalapaku తమలపాకు (Telugu), विड्याचे पान or "नागलीचे पान"(Marathi), નાગરવેલ ના પાન or Naagarvel na paan (Gujarati), veeleyada yele ವೀಳೆಯದ ಎಲೆ (Kannada), Vettila (Malayalam), Kun (ကွမ်း) in Burmese, Plū (Mon), Malus (Tetum), Maluu (Khmer), Plū (Thai: พลู), Bulath බුලත් (Sinhalese), Malu (Tokodede), Bileiy (Maldivian: ބިލެތް), bulung samat (Kapampangan), daun sirih (Malaysian), daun sirih/suruh (Indonesian),Kebui(Palauan), Pupulu (Chamorro), Ikmo (Tagalog), Gawed (Ilokano),Pu (ພູ) in Lao, and Trầu (Vietnamese), Gaweud/Gawed in (Kalinga), Buyo (Bikol).