Researchers at the Ramazzini Institute for cancer research in Italy published a study in Environmental Health Perspectives earlier this year, which they say shows that aspartame causes lymphomas and leukaemia in female laboratory animals "at doses very close to the acceptable daily intake for humans".
They also say that while rats fed aspartame ate less food, there was no difference in body weight between treated and untreated animals.
Following initial discussions with the Ramazzini Institute in June 2005 and prior to the study's publication, EFSA pledged to review the significance of the new findings. It renewed its request that the institute provide it with the primary data in November.
Up until now the regulator has not been urging consumers to avoid aspartame, which is used in more than 6,000 food and drink products in the EU and as a table-top sweetener.
"Based on current evidence on the safety of aspartame, EFSA does not recommend that consumers who wish to choose foods containing aspartame make any changes to their dietary habits," it said in an earlier statement.
EFSA has indicated that its Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC) will evaluate data from the new study "in the context of previous extensive safety data available".
Various food associations have dismissed the Ramazzini study, saying it did not follow established scientific procedures.
Aspartame was first authorised for use by several EU member states in the 1980s. European legislation harmonising its use in foodstuffs was introduced in 1994 following safety evaluations in 1984, 1987, 1988.
Since then there has been ongoing debate amongst scientists and the media about the safety of aspartame itself and its components, aspartic acid, phenylalanine and methanol, although so far the fears have not been borne out by the available evidence.
A further review of all the original and more recent data on aspartame was carried out in 2002 by the EC Scientific Committee for Food.
Both published and unpublished data, including all the information on genotoxicity and carcinogenicity in animals and humans, were considered at that time and the SCF re-confirmed the previously established acceptable daily intake (ADI) for aspartame.