Betel nut

The areca palm is a slender, tall, feather-leaved palm bearing clusters of smooth, orange-red fruits about the size of a small egg. Inside the fibrous husk lies a single hard seed, round to conical, with a marbled brown-and-white interior like a nutmeg.

The seed is firm and astringent with a bitter, tannin-like taste, and chewing it stimulates saliva that stains the mouth red when combined with betel leaf and lime.

It is sold fresh, dried, sliced, boiled, cured or packed in sweetened flavoured mixtures such as supari or gutka, as well as in whole nuts for chewing.

Areca catechu is believed to be native to tropical Asia, with a probable origin in the Malay Archipelago and the Philippines. Archaeological evidence, including areca remains in burials in Thailand and the Philippines, suggests human use at least several thousand years ago.

The palm was spread by people across South Asia, mainland Southeast Asia, southern China, Taiwan, the Pacific Islands and parts of East Africa.

The common name betel nut is a misnomer, since betel is the leaf of a different plant, Piper betle, which is wrapped around the seed. The word areca comes from a Malayalam name, adakka, and the Latin species name catechu comes from a word for an astringent extract.

Chewing the areca seed in a betel leaf quid is one of the oldest and most widespread habits of Asia and the Pacific. The practice is described in Indian Sanskrit texts and in Sri Lankan chronicles, and it appears in ancient Chinese and Roman accounts of travellers.

It has played a role in rituals and etiquette, from wedding gifts and hospitality offerings in South Asia to ceremonial exchange in Melanesia. Silver and brass betel boxes and spittoons became elegant objects at the courts of India, Thailand and Malaysia.

In the colonial era the trade in areca nut was substantial, linking producers in India, Sri Lanka and Indonesia to consumers across the region. In the 20th century, flavoured, packaged chewing products appeared, such as gutka in India.

Health authorities, including the International Agency for Research on Cancer, classified areca nut as carcinogenic to humans, and many countries have tried to regulate or restrict its sale. Despite that, it is still chewed by hundreds of millions of people.

The main use is as a chewing stimulant. A slice or piece of seed is wrapped with betel leaf, often with slaked lime and sometimes with spices, sweeteners or tobacco, to form a quid known as paan in India. It is also offered at social and religious occasions.

Aside from chewing, areca extracts have been used in traditional medicine as a vermifuge and digestive, and for dyeing cloth and tanning.

In veterinary traditions, areca seed was used to treat worms. The palm is also valued as an ornamental and its husk fibre has local uses.

The seed contains alkaloids, notably arecoline, which stimulates the nervous system and produces mild alertness and a feeling of warmth. Habitual chewing is associated with oral submucous fibrosis, oral and oesophageal cancers, dependency and cardiovascular and metabolic problems.

Traditional claims of digestive benefit are not outweighed by these risks, and public health agencies discourage the habit. There is no recommended safe level for regular chewing.