[Betel - the fourth most popular substance in the world].

Betel is a kind of substance for chewing, that is made from piper betle, areca nuts and other, additional constituents. It is the fourth most popular psychoactive substance in the world, right after caffeine, nicotine and alcohol. It is particularly famous in Asia. Betel chewing induces euphoria and it is addictive. Similarly like in other substances such as nicotine or alcohol, betel also has detrimental effects. It causes e.g. oral cancer and cancer of the oesophagus, it contributes to the development of metabolic syndrome, liver cirrhosis and chronic kidney disease. There are also positive effects of chewing betel, because is has antioxidant, anti-inflammatory, antyparasitic and antiseptic properties. The aim of this paper was to expand knowledge about betel and its both: positive and negative influence on human health. In this article original and review papers associated with the topic were used.