The apple cider vinegar weight loss study withdrawn following integrity review. See what it found.
The BMJ Group has retracted a widely publicised study that claimed daily consumption of apple cider vinegar could promote weight loss in people with overweight or obesity.
The decision follows a detailed integrity review that uncovered multiple statistical and methodological problems.
The small clinical trial, published in BMJ Nutrition, Prevention & Health in March 2024, received global media attention after a press release highlighted its findings. The research continues to be cited in news articles, blogs and consumer health commentarires.
The study recruited 120 overweight and obese individuals who were randomly assigned to either an intervention group receiving five, 10 or 15 mL of ACV or a control group receiving a placebo over a 12-week period.
Measurements of anthropometric parameters, fasting blood glucose, triglyceride and cholesterol levels were taken at weeks zero, four, eight and 12.
“Our findings showed that daily consumption of the three doses of ACV for a duration of between four and 12 weeks is associated with significant reductions in anthropometric variables (weight, body mass index, waist/hip circumferences and body fat ratio), blood glucose, triglyceride and cholesterol levels,” the authors wrote.
They said “no significant risk factors were observed during the 12 weeks of ACV intake”.
“Consumption of ACV in people with overweight and obesity led to an improvement in the anthropometric and metabolic parameters,” the researchers concluded.
“ACV could be a promising antiobesity supplement that does not produce any side effects.”
Concerns about the reliability of the trial emerged soon after publication, including critiques published as letters to the editor.
Following these, BMJ’s content integrity team launched a review, referring the study to independent statistical experts.
Their investigation revealed multiple errors in statistical analysis, implausible values, irregularities in the dataset and results that could not be reproduced.
The experts concluded that the underlying participant-level data would require independent scrutiny before any reliable conclusions could be drawn. In addition, the study had not been prospectively registered, in breach of BMJ editorial policy, and methods were inadequately reported.
“It wasn’t possible for the statisticians to replicate the results and multiple analytical errors were identified,” the BMJ Group said in a media statement.
“There were also irregularities in the data set, and their report, which is appended to the retraction notice, concluded that the data collected from each participant would require further independent scrutiny.
“The authors said that the identified errors were honest mistakes, but they agree with the decision to retract the study.”
Dr Helen Macdonald, the BMJ Group’s Publication Ethics and Content Integrity editor, said it was important to prevent ongoing misrepresentation of unreliable results.
“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,” she said.
“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.
“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.”
Professor Martin Kohlmeier, editor-in-chief of BMJ Nutrition Prevention & Health explained the decision to publish the study despite the lack of trial registration.
“In hindsight, this was the wrong decision to make,” he said.
“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.”
See the BMJ’s full retraction statement here.
BMJ Nutrition Prevention & Health is co-owned with NNEdPro Global Institute for Food, Nutrition and Health
