Systematic review and evaluation of aspartame carcinogenicity bioassays using quality criteria.
Level 5 - mechanism / opinion, no new human data
Systematic review of animal carcinogenicity bioassays without human data
PubMed 29339245 · doi:10.1016/j.yrtph.2018.01.009
What was done
A systematic review evaluated the quality of animal cancer bioassays of aspartame using the Klimisch grading system. Nine studies with complete histopathology were appraised: three 2-year studies by Searle, three transgenic mice studies by the National Toxicology Program (NTP), and three lifetime studies by the Ramazzini Institute. A tenth study restricted to brain tumors was not rated.
What was found
Zero studies met the criteria for Klimisch Code 1 (reliable without restrictions). Six studies were rated Klimisch Code 2 (reliable with restrictions): three pre-GLP Searle studies and three NTP transgenic mouse studies, which demonstrated no carcinogenic potential. The three Ramazzini Institute lifetime studies were rated Klimisch Code 3 (not reliable) due to high background rates of spontaneous tumors in animals dying near end of life, tumor diagnostic concerns, and chronic infections. No numerical risk ratios or tumor counts were provided in the abstract.
Why it matters
The paper contextualizes contradictory rodent cancer data on aspartame by attributing positive carcinogenicity findings to methodological weaknesses in lifetime animal protocols.
Limits
The review evaluates rodent bioassays rather than human health outcomes. None of the included animal studies achieved top-tier reliability (Klimisch Code 1), and quantitative effect estimates were not reported in the abstract.
Cited by
- context Approximately 80% of studies evaluating aspartame show no effect on cancer risk.