Qat chewing and cancer: pesticide or leaf?

Published online 7 October 2010

Abdulhakim Mahmoud

A man chews qat in Sana'a, Yemen.
A man chews qat in Sana'a, Yemen.
Wikimedia Commons


Qat, a staple, narcotic plant cultivated widely in Yemen for its mild stimulant effect, might be causing a surge in oral cancers in the poorest country in the Middle East.

"The UN Integrated Regional Information Networks have reported that about 30% of Yemeni cancer patients suffer from mouth or gum cancer," said Nadim Sa'eed, director of the National Cancer Centre in Sana'a.

During the 4th Gulf Cooperation Council Conference on Fighting Cancer, held February in Sana'a, the Yemeni ministry of public health and population attributed the increased incidence of cancer to the use of illegal pesticides, such as methyl bromide, in qat1 farming.

Mahmoud Sarhan, director-general of the King Hussein Cancer Center in Jordan, says the problem could lie in the qat leaves themselves, not the pesticides used. "After a few days, pesticides are not active anymore and easily washed away. However, chewing qat with fresh pesticides on them is hazardous and might be associated with cancer."

Qat is chewed daily by most people in Yemen. During the early hours of noon, thousands of Yemenis retire to shaded or cool areas to chew the leaves for their stimulant effect, which is generally accepted as an integral act in socializing.

The leaves contain the alkaloid cathinone, which has an amphetamine-like effect. The plant is an illegal substance in many countries, but is not controlled in Yemen and Somalia.

Earlier this year, a retrospective study conducted in Sana'a and Aden in Yemen suggested that the high number of head and neck cancers in Yemen was a result of prolonged exposure to carcinogens in qat1.

"We studied the effects of qat on upper gastrointestinal tract in Yemeni patients. Regular daily qat chewing was not associated with any major effect on the oesophagus or stomach, but duodenal ulcers were more common in chewers," says Ahmed Al-Haddad, assistant professor of Sana'a University.

However, Ahmed Badheeb, an oncologist at Hadramaut University, Yemen, and head of the Hadramaut Cancer Foundation, countered that "there is still no medical evidence that proves that the use of chemical pesticides in growing of qat causes cancer."

According to Sa'eed, the issue is complicated by a lack of reliable national data. "Our cancer centre was only founded in 2008, so we only just started working on a national cancer register which will make our data more reliable."


  1. Abdul-Hamid, G. et al. Pattern of head and neck cancer in Yemen. Gulf J Oncolog. 7, 21-24 (2010). | PubMed |