BMJ Group retracts apple cider vinegar weight-loss study after data concerns

The BMJ Group has retracted a study that claimed a daily shot of apple cider vinegar could trigger meaningful weight loss in overweight and obese adults, more than a year after it was published in BMJ Nutrition, Prevention & Health. The paper, led by scientists at the Holy Spirit University of Kaslik in Lebanon, reported that participants who drank a 15 ml measure before breakfast over 12 weeks lost about 11 pounds (5 kilograms) and reduced their body-mass index by 2.7 to 3.0 points, depending on the dose. Those given a placebo lost about 0.3 kilograms in the same period. The retraction notice cited multiple analytical errors and irregularities in the data set, signaling that the observed effects could not be trusted.

The study, published in 2020, enrolled 120 participants who were overweight or obese with a BMI between 27 and 34 and divided them into four groups of 30. Three groups consumed a daily apple cider vinegar shot before breakfast in various doses—5, 10, or 15 milliliters—while a fourth group received a placebo liquid. Over the 12-week trial, participants tracked their diet and physical activity. At the time, the results were described by some researchers as remarkable, given the simplicity of the intervention, but the publication immediately drew scrutiny from nutrition scientists concerned about the study’s design and data interpretation.

Critics pointed to several methodological weaknesses. Notably, some participants were not weight-stable at baseline, meaning they could have been on a weight-loss trajectory before the intervention began. Diet and activity were self-reported, raising questions about whether lifestyle changes could account for the weight losses rather than the vinegar itself. Researchers did not report whether participants used weight-loss medications, a factor that could confound results. In August 2020, nutrition experts highlighted that the study relied on t-tests and did not describe total dietary intake or caloric changes, limiting confidence in causal conclusions. These concerns prompted an internal BMJ Group review aimed at evaluating the reliability of the findings and the publication process.

The retraction notice said the BMJ Group could not replicate the results and that multiple analytical errors were identified after statistical evaluation. The editors stressed that while honest mistakes can occur, the integrity of the scientific record must be maintained. Dr. Helen Macdonald, the group’s publication ethics and content integrity editor, said the decision reflects a commitment to openness and correcting the record, noting that investigations in nutrition science are complex and can take months to complete. She emphasized that readers should not rely on the unreproduced findings as evidence of a weight-loss effect from apple cider vinegar.

Professor Martin Kohlmeier, editor in chief of BMJ Nutrition Prevention & Health, acknowledged that the decision might be viewed in hindsight as the wrong one, but he defended the journal’s emphasis on high-quality evidence. He said the authors come from an scientific environment that is underrepresented in nutritional research, and the journal aims to prioritize rigorous evidence, often from larger clinical trials that are challenging to conduct due to participant numbers and time requirements.

Beyond the specifics of this trial, apple cider vinegar remains a popular consumer product with a robust market. The liquid, available in “with the mother” or filtered forms, is touted by proponents for a range of health benefits, though scientific consensus on long-term effects remains divided. The cost of a bottle can be as low as £2.50 in health food stores, a detail highlighted in media coverage that has often linked celebrity endorsements to consumer interest. Celebrities such as Elizabeth Hurley and Jennifer Aniston have publicly promoted the practice, and Victoria Beckham in 2020 shared a morning routine involving two teaspoons of vinegar, illustrating the broader cultural context in which such studies gain attention.

The retraction underscores ongoing challenges in nutritional research, where small trials with self-reported data and limited demographic diversity can yield striking claims that require careful verification. The BMJ Group’s action reflects a broader commitment to ensuring that published results are robust, reproducible, and aligned with established scientific standards. While the case may temper enthusiasm for apple cider vinegar as a weight-management aid, experts say it also reinforces the need for rigorous, well-controlled clinical trials to evaluate popular health practices. As researchers continue to explore the biology of insulin sensitivity, energy metabolism, and gut microbiota, the episode serves as a reminder that extraordinary claims require extraordinary evidence and transparent methodologies.