The quality of nutrition and cancer reviews: a systematic assessment

The methodological quality of published reviews of nutrition and cancer (2008-2009) and of the carcinogenicity of acrylamide (1999-2009) was systematically assessed. Each review was examined with respect to four characteristics: whether the purpose of the review was explicitly stated, whether a methods section (detailing the methods used to "weigh" the evidence) was included, whether "weight of evidence" methods were described elsewhere in the paper (e.g., in the discussion), and finally, whether references to recognized "weight of evidence" methods were included. In this study, ninety per cent of a systematically selected sample of recent reviews on nutrition and cancer published in 2008-2009 and 74% of reviews on acrylamide on cancer published in 1999-2009 were found to be methodologically troublesome or frankly unsound. Failure of peer review and editorial oversight are possible explanations, suggesting a broad lack of concern about this issue in the scientific community. If peer reviewers in the nutrition and cancer community do not require "weight of evidence" methods, then these methods may not appear in the published reviews. Similarly, if journal editors (or editorial policies) do not require methods sections in literature reviews, then these sections may not appear. The prerogative of the author(s) seems the most likely determinant of whether a systematic approach is used or not in nutrition and cancer reviews.