Last week, the publisher retracted a study published in BMJ Nutrition, Prevention & Health in March 2024 that suggested that small daily quantities of apple cider vinegar might support weight loss in the overweight or obese.
The retraction was prompted by concerns raised about the quality of the work, including the approach 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, which BMJ Group says breaches its editorial policy.
“In hindsight, this was the wrong decision to make,” Professor Martin Kohlmeier, editor in chief of BMJ Nutrition Prevention & Health, said of the choice to publish despite the lack of trial registration. “But the authors come from a scientific environment that is underrepresented in nutritional research, and the journal aims to prioritize high quality evidence, which usually comes from clinical trials.”
He noted that clinical trials are unusual in nutritional research as they can be challenging to undertake because of the numbers of participants and time needed to obtain meaningful results.
Overcoming temptation, correcting the scientific record
The retraction responded to critiques submitted by journal readers, which included a letter published in the journal titled “Improbable data characteristics and extreme effects of apple cider vinegar on weight loss”. The letter authors from Boise State, Duke and Linnaeus universities questioned the suitability of the statistical analysis, the highly improbable data distributions and incongruency with past research on apple cider vinegar.
“Given the potential public health and economic impact of these findings, we hope the researchers will provide a satisfactory response to these observations and will adhere to their stated data availability commitments to enable independent review of the data,” they wrote.
Following a review by BMJ Group’s content integrity team, the study was referred to statistical experts who were unable to replicate the findings and identified multiple analytical errors and irregularities in the data set. They stated that these issues would require further independent scrutiny.
“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,” Dr. Helen Macdonald, publication ethics and content integrity editor at BMJ Group, shared in a press release.
“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.”
She added that while the publisher addresses allegations as swiftly as possible, reaching a sound, fair and final decision can take several months to ensure that due process is followed in often complex investigations.
‘Honest mistakes’
The double-blind, placebo-controlled study, was conducted by researchers from Holy Spirit University of Kaslik and the American University of Science and Technology in Lebanon.
They recruited 120 Lebanese adolescents and young adults with overweight or obesity who were randomly assigned to receive either a lactic acid placebo or 5 mL, 10 mL or 15 mL of apple cider vinegar containing 5% of acetic acid diluted in 250 mL of water daily for 12 weeks.
Findings indicated that supplementation with all three doses of apple cider vinegar was associated with significant reductions in weight, body mass index, waist/hip circumferences and body fat ratio, as well as a dose-dependent decrease in blood glucose, triglyceride and cholesterol levels.
“The results might contribute to evidence-based recommendations for the use of [apple cider vinegar] as a dietary intervention in the management of obesity,” the Lebanese research team wrote. “The study could stimulate further research in the field, prompting scientists to explore the underlying mechanisms and conduct similar studies in other populations.”
The retraction notice, however, highlighted that the dataset supplied by the authors demonstrated patterns inconsistent with random allocation of participants to treatment groups and improbably small P-values given the limited number of participants included in the study.
“The authors state that the discrepancies were honest mistakes that arose from version mismatches, data rounding or formatting differences when exporting from statistical software to reporting spreadsheets,” the notice reads.
NutraIngredients reached out to the study authors for comment but did not hear back prior to publication.
