Betel nuts tasting a bit metallic?

It's estimated that one-tenth of the world's population chews betel nuts, the astringent, addictive seeds of the betel palm. Researchers have associated chewing betel nuts with mouth cancer since 1984 but hadn't been able to pinpoint the precise connection. Now, a study suggests copper may be the culprit.

Betel nuts, also called areca nuts, are widely sold and consumed in southern Asia. Using a spectrophotometer to analyze content, researchers at the Royal College of Surgeons and Dental Science at Kings College in London find that the average betel nut snack contains from 1.5 to 10 times more copper than similar snacks consumed in Great Britain. They report in the May 17 Lancet that saliva tests of people chewing 3 grams of packaged betel nuts turned up high concentrations of copper. Absorption is difficult to measure, but the researchers estimate that an adult in India could ingest five times as much copper daily as the typical U.S. citizen.

Earlier research linked betel nut chewing to a buildup of scar tissue under the mucus membrane, a precancerous condition. The London researchers suggest that copper may dam age some genes, leading to this buildup. Copper has also been linked to liver scarring and scleroderma, a rare autoimmune disease that causes degeneration of connective tissues and can damage blood vessels.