Cape Town - New research has established a link between the consumption of home-brewed traditional beer and oesophageal cancer.
The beer had been associated with increased risk of cancer, but a new study has shown for the first time that the drink contains carcinogens .
The study appears in the latest issue of the South African Medical Journal.
Researchers from Wits University have linked the incidence of oesophageal squamous cell carcinoma (SCC) in black South Africans to carcinogenic nitrosamines (chemical compounds) found in traditional beer, commonly known as Umqombothi.
Analysing cancer records over a period of almost a century – between 1912 to 2010 – researchers linked the cancer to a major dietary change at the turn of the 20th century where black people changed their staple diet from sorghum to maize. Maize, particularly fermented maize, used in traditional beer, has been linked to the high incidence of oesophageal squamous cell carcinoma due to the fungus Fusarium moniliforme, which grows freely on maize, but less so on sorghum.
Toxins produced by this fungus cause a chemical reaction in the maize, resulting in the occurrence of carcinogenic nitrosamines.
Researchers analysed traditional maize beer specimens. Using molecular docking studies to determine the interaction of nitrosamines and protein that is found in the oesophageal wall, they found all six 20ml samples tested contained carcinogens NDMA, NDEA and NPYR.
Researchers said while these compounds had been shown to produce cancer experimentally, up to now there had been no conclusive evidence to show that they were carcinogenic to humans.
In 2009, the United States Environmental Protection Agency listed these nitrosamines as “probably carcinogenic to humans”.
The researchers also analysed the results of cancer records from the South African Institute for Medical Research, which showed that even though there were no documented cases of this form of cancer among the country’s population between 1912 and 1927, there had been an increase in oesophageal cancer in the 1930s with an average of four cases a year.
This number increased over time, and between 1940 and 1949 more than 160 cases of oesophageal cancer were recorded. The figures peaked in 1987, reaching 255 cases.
The numbers started to decline after 1987, and for the past 10 years there has been an average of 41 cases a year – a period which is linked to the diminished consumption of traditional beer due to the increased availability of other sources of liquor.
Lead researcher and Professor of Pharmaceutics, Viness Pillay said: “The premise of the current study is that carcinogenic nitrosamines in the fungal-infected traditional maize-brewed beer are the cause of squamous cell carcinoma of the oesophagus.
“Based on a comparison with the N-nitrosamine mix standards, NDMA, NPYR and NDEA, all carcinogenic nitrosamines, were identified in the traditional beer samples.”
He said the study was the first to demonstrate carcinogenic nitrosamines in traditional beer.
Cape Argus