COFFEE drinkers who have stoically ignored every attack on their morning poison have a new peril to contend with. Ochratoxin A, a contaminant produced by moulds that grow on coffee beans, has been linked with kidney cancer. But it was thought to be destroyed when beans are roasted and processed. Now researchers in Switzerland have shown that the chemical ends up in cups of coffee after all.
鈥淲e found out that it鈥檚 not destroyed by roasting, and it goes into the brew after filtering,鈥� says Christian Schlatter of the Swiss Federal Institute of Technology in Zurich.
The concentration of ochratoxin A is already monitored in some foodstuffs where it is known to be a problem, notably cereals, pig kidneys and black pudding. In these products, the contaminant can reach a concentration of 45 micrograms per kilogram.
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Schlatter says that the concentrations he has measured in coffee are very low, with a maximum of around 5 micrograms per kilogram of ground coffee. His preliminary toxicological experiments in rats suggest that the risk of kidney cancer may be increased by 1 per cent.
Government analysts across Europe have begun checking coffee beans for signs of ochratoxin A. 鈥淲e have absolutely no indications that the range we鈥檝e found [in Zurich] is the range you will find in other coffees,鈥� says Schlatter.
In Britain, the Ministry of Agriculture, Fisheries and Food has asked the Leatherhead Food Research Association in Surrey to make random checks on samples of coffee. Although Schlatter鈥檚 work focused on freshly ground coffee, MAFF has asked Leatherhead to examine instant coffees as well. 鈥淚鈥檓 concerned to know how much of a problem there is, and it will depend on how the raw material is stored and processed,鈥� says Peter Farnell, who heads the team at Leatherhead.
In the Netherlands, investigations at the University of Utrecht have shown that breakdown products of ochratoxin A are potentially more toxic than the original compound. 鈥淥chratoxin A is converted into mutagenic metabolites by human enzymes,鈥� says Joan Fink-Gremmels, professor of veterinary toxicology.
Fink-Gremmels says that in the light of her team鈥檚 findings, the Joint FAO/WHO Expert Committee on Food Additives is reviewing its safe limit for consumption of ochratoxin A. At present, the committee鈥檚 鈥減rovisional tolerable weekly intake鈥� is 112 nanograms per kilogram of body weight.
The Department of Health鈥檚 expert committees on mutagenicity and carcinogenicity say that ochratoxin A damages chromosomes, and causes cancer in animals.