In August 1999, it was announced that research would be undertaken on aspartame at King's College London. At the time, NutraSweet AG, now Ajinomoto Switzerland AG, issued a statement welcoming any well-conducted research into the safety of aspartame.

Four years on, the Samantha Dickson Research Trust, the UK charity which sponsored the research, has published the following summary.

EVALUATION OF THE DIETARY ADDITIVE ASPARTAME (NUTRASWEET) AS A RISK FACTOR FOR CENTRAL NERVOUS SYSTEM TUMOURS.
King's College, London. Professor G. Pilkington, Dr. P. Nunn

This study found that Aspartame and its derivatives

1. Do not appear to interact with cellular macromolecules
2. Do not cause biochemical changes characteristic of reactive molecules
3. Lacks the activity normally associated with direct carcinogens
4. Do not cause DNA damage as defined by comet assay

In summary, taken together with data from the literature, it is concluded that Aspartame and the breakdown products studied is not carcinogenic.