Suspicions about the validity of research by Professor Ranjit Kumar Chandra, a prominent Canadian researcher, have been raised by three journals, including the BMJ.

The latest concern, in an editorial and a letter in the November issue of Nutrition (2003;19: 955-6 and 976-80) question research published in that journal by Professor Chandra in September 2001 (17:709-12).

The Nutrition study was a randomised, blind, placebo controlled trial. It showed that a specific multivitamin and mineral supplement could improve cognitive function in people aged over 65 years. Professor Chandra, who was the sole author, concluded that the supplement might delay the onset of Alzheimer's disease.

The original paper and the most recent letter and editorial questioning its validity have attracted considerable media attention.

The BMJ's statistical reviewer concluded that the data had “all the hallmarks of being entirely invented.”

The 2001 paper in Nutrition is almost identical to a paper submitted to the BMJ in October 2000, which followed up a trial published in the Lancet in 1992 (340: 1124-7)

The BMJ paper was not published because of serious problems identified during peer review. These problems included the lengthy period between the Lancet trial and submission of the manuscript on the same set of data to the BMJ and doubts that a major trial could have been undertaken by one man, who, …