- A 2025 ketogenic diet study published in JACC has been retracted due to flawed analysis and selective reporting.
- The study found no significant increase in coronary artery calcium scores for keto dieters over a 1-year period.
- However, experts criticized the study’s short follow-up window, citing the need for longer-term studies.
- The retraction undermines a key piece of evidence supporting the cardiovascular safety of long-term keto diets.
- The decision affects clinical guidance, nutritional policy, and consumer trust in diet science.
The Journal of the American College of Cardiology (JACC) has retracted a 2025 study that claimed the ketogenic diet did not accelerate arterial plaque formation, citing selective reporting, questionable statistical methods, and insufficient follow-up duration. The retraction, announced in May 2026, follows widespread criticism from epidemiologists and cardiologists who flagged inconsistencies in how data on coronary artery calcium (CAC) progression was analyzed and presented. The study, which had been cited to support the cardiovascular safety of long-term keto diets, is now formally invalidated—undermining a key piece of evidence used in public health debates. This retraction matters because it affects clinical guidance, nutritional policy, and consumer trust in diet science, particularly as low-carbohydrate regimens grow in popularity despite ongoing concerns about heart health.
Why the Keto Study Raised Red Flags
The 2025 JACC paper, authored by a single researcher and presented as a randomized observational follow-up, claimed that participants on a ketogenic diet showed no significant increase in coronary artery calcium scores over a one-year period compared to a control group. This finding was widely publicized by low-carb diet advocates as proof of cardiovascular neutrality or even benefit. However, experts immediately questioned the short follow-up window—just 12 months—given that arterial calcification typically develops over years or decades. Additionally, the study reported only a subset of cardiovascular endpoints, omitting key markers like lipid profiles, inflammatory biomarkers, and carotid intima thickness, raising concerns about selective outcome reporting. Such omissions are a known risk in nutrition research, where findings can be shaped by which data are highlighted or hidden.
Flawed Methods and Lack of Peer Oversight
The retracted study followed a cohort of 120 adults with obesity or prediabetes, randomized into either a ketogenic diet group (less than 50 grams of carbohydrates daily) or a standard dietary counseling group. The primary endpoint was change in CAC score after one year. However, critics noted that CAC progression is rarely detectable in such a short timeframe, making the null result statistically underpowered and clinically questionable. Further scrutiny revealed that the statistical model used did not adjust for baseline CAC levels or key confounders like LDL cholesterol trajectories and physical activity. The fact that the study had only one author also drew skepticism, as major clinical nutrition studies typically involve multidisciplinary teams for data validation and bias control. According to Retraction Watch, the journal received multiple letters expressing concern before initiating its investigation.
Roots of the Problem in Nutrition Science
The retraction underscores deeper issues in nutritional epidemiology, where funding sources, researcher bias, and short-term study designs often compromise long-term conclusions. Keto diet research, in particular, has been polarizing: while some short-term trials show benefits in weight loss and insulin sensitivity, long-term cardiovascular outcomes remain uncertain. A 2023 meta-analysis published in Nature Reviews Cardiology warned that low-carb diets high in animal fats are associated with a 20% higher risk of coronary heart disease over 10 years. The retracted JACC paper ran counter to this body of evidence, fueling suspicions of analytical cherry-picking. Experts argue that single-outcome, short-duration studies are insufficient to assess chronic disease risk and that reliance on them distorts public understanding. The incident highlights the need for preregistered protocols, independent data audits, and transparent reporting standards in dietary trials.
Impact on Patients and Public Health Guidance
The retraction affects clinical recommendations, patient decision-making, and public health messaging. For months, the study was cited by influencers and clinics promoting keto as heart-safe, potentially influencing thousands of individuals with diabetes or cardiovascular risk factors. Now, clinicians must correct misinformation and reaffirm that the long-term cardiovascular effects of ketogenic diets remain unclear. Regulatory bodies like the American Heart Association and the WHO continue to recommend balanced, plant-rich diets over extreme macronutrient restriction. The episode also damages trust in peer-reviewed journals, especially when high-impact findings are later invalidated. Patients may become skeptical of all nutrition science, even robust studies, if retractions of flawed papers are not clearly communicated.
Expert Perspectives
Cardiologist Dr. Neha Patel of Johns Hopkins called the retraction “a necessary correction but a preventable failure,” noting that peer review should have caught the methodological weaknesses earlier. In contrast, keto advocate Dr. Eric Westman, who was not involved in the study, suggested that the retraction reflects “institutional bias against low-carb research,” though he acknowledged the short follow-up as a limitation. Most experts agree that while the keto diet has therapeutic value in specific conditions like epilepsy and type 2 diabetes, generalizing its safety based on flawed data is dangerous. The consensus is that dietary recommendations must be grounded in long-term, rigorously conducted trials.
What’s next is a broader reckoning with how nutrition research is conducted and validated. Scientists are calling for stricter journal standards, including mandatory data sharing and preregistration of analysis plans. The retracted paper may prompt JACC and other cardiology journals to tighten review protocols for diet studies. Meanwhile, ongoing trials like the DIETFITS extension and the Keto-Med study will provide more reliable data in the coming years. Until then, patients and providers should remain cautious about dramatic claims—especially those based on single-author, short-term studies with selective outcomes.
Source: Reddit