BMJ Group has retracted research which linked small daily quantities of apple cider vinegar with weight loss after saying that at present, the results of the study are “unreliable”.
The findings of the small trial appeared in BMJ Nutrition, Prevention & Health in March 2024, but following an extensive review, it was found to have breached BMJ Group’s editorial policy and journalists have been advised that the research should no longer be referenced.
The study, which indicated that small daily quantities of apple cider vinegar may help people who are overweight or obese to lose weight, received international attention at the time.
However, concerns were raised about the quality of the study, including the approach taken to statistical analysis of the data; implausible statistical values; the reliability of the raw data; inadequate reporting of methods; and lack of prospective trial registration.
This prompted a review by BMJ Group’s content integrity team, which then referred the research to statistical experts to assess the reliability of the findings.
They found they were unable to replicate the results of the study, and a number of analytical errors were discovered. In addition, there were irregularities in the data set, with the team reporting that data from each participant would need further independent analysis.
Dr Helen Macdonald, BMJ Group’s Publication Ethics and Content Integrity Editor, said: “Tempting though it is to alert readers to an ostensibly simple and apparently helpful weight loss aid, at present the results of the study are unreliable, and journalists and others should no longer reference or use the results of this study in any future reporting.
“This retraction reflects our strategic and proactive approach to investigating concerns raised about the content we publish. We act where necessary in the interests of openness and the importance of correcting the scientific record.
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“While we deal with allegations as swiftly as possible, it’s very important that due process is followed. Investigations are often complex. This one involved detailed scrutiny of data and correspondence with researchers, institutions, and other experts, for example. Reaching a sound and fair and final decision can therefore take several months.”
The study authors said honest mistakes were made and they agreed with the decision to pull the research.
Addressing the decision to publish the study despite the absence of trial registration, Professor Martin Kohlmeier, editor in chief of BMJ Nutrition Prevention & Health, said: “In hindsight, this was the wrong decision to make. But the authors come from a scientific environment that is underrepresented in nutritional research and the journal aims to prioritise high quality evidence, which usually comes from clinical trials.
“These are relatively unusual in nutritional research as they can be challenging to undertake because of the numbers of participants and time needed to obtain meaningful results.”
