Anorexia nervosa is a serious eating disorder that causes severe malnutrition and can damage the liver. Doctors typically check liver health using standard blood tests, but researchers discovered something unexpected: people with anorexia often have unusually high levels of vitamin B12 in their blood. In this study of patients treated at a Japanese hospital, scientists found that higher vitamin B12 levels were connected to worse liver damage and more severe malnutrition. This suggests that measuring vitamin B12 alongside standard liver tests might help doctors better understand how sick someone is and how badly their liver is affected.

The Quick Take

  • What they studied: Whether high vitamin B12 levels in the blood are connected to liver damage and severe malnutrition in people with anorexia nervosa
  • Who participated: Patients diagnosed with anorexia nervosa who received treatment at a Japanese hospital between 2012 and 2021. The study excluded people with alcohol problems, cancer, or those taking vitamin supplements
  • Key finding: People with anorexia who had very high vitamin B12 levels (over 4000 pg/mL) had lower body weight and higher liver enzyme levels, suggesting their bodies were more severely damaged by malnutrition
  • What it means for you: If you or someone you know has anorexia, doctors may want to check vitamin B12 levels as an additional sign of how serious the malnutrition is and whether the liver is being harmed. This is not a replacement for standard medical care but an additional tool doctors might use

The Research Details

This was a retrospective observational study, which means researchers looked back at medical records from patients who had already been treated at the hospital. They collected information about patients with anorexia nervosa who visited the outpatient clinic or were admitted to the hospital between April 2012 and March 2021. The researchers measured three things from blood tests: liver enzymes (AST and ALT), vitamin B12 levels, and body mass index (BMI, which is a measure of body weight relative to height). They excluded patients who had other conditions like alcohol use disorder or cancer, or who were taking vitamin supplements, because these could affect the results.

The researchers then analyzed whether there were connections between these measurements. They looked at whether people with lower body weight had different liver enzyme levels, and whether vitamin B12 levels were related to both body weight and liver damage. This type of study is useful for finding patterns in medical data, but it cannot prove that one thing causes another—it can only show that things tend to happen together.

This research approach is important because anorexia nervosa is a serious condition that affects many organs, including the liver. By looking at existing medical records, researchers can identify patterns without needing to do new experiments on sick patients. Understanding these patterns helps doctors recognize warning signs of severe malnutrition and liver damage. The fact that vitamin B12 levels appear to be connected to both body weight and liver damage suggests this measurement could be a useful additional tool for doctors to assess how serious someone’s condition is.

This study has some strengths and weaknesses readers should understand. The strength is that it looked at real patient data from a hospital over many years, which gives a realistic picture of what happens in actual medical practice. However, because it only looked at records from one hospital in Japan, the results might not apply to all populations. The study also didn’t explain why vitamin B12 levels get so high in anorexia—it only showed that they do. Additionally, the exact number of patients studied was not clearly specified in the abstract, which makes it harder to judge how reliable the findings are. The researchers acknowledge that more research is needed to understand the mechanisms behind these findings.

What the Results Show

The main finding was that vitamin B12 levels were significantly elevated in people with anorexia nervosa, and these high levels were connected to signs of more severe illness. Specifically, people with very high vitamin B12 levels (above 4000 pg/mL) had lower body weight compared to those with normal vitamin B12 levels, indicating more severe malnutrition. Additionally, higher vitamin B12 levels were associated with higher liver enzyme levels (both AST and ALT), which are markers of liver damage.

The study also found that body weight (measured as BMI) was negatively correlated with liver enzymes, meaning people who weighed less tended to have more signs of liver damage. This makes sense because severe malnutrition from anorexia can harm the liver. The connection between vitamin B12 and liver damage was particularly interesting because it suggests these two things may be related in ways doctors don’t yet fully understand.

These findings suggest that vitamin B12 levels might be a useful additional indicator—along with standard liver enzyme tests—for doctors to assess how severe someone’s malnutrition is and how much their liver has been affected. The researchers emphasize that this is a possible supportive indicator, not a definitive test on its own.

The study found that the relationship between body weight and liver damage was consistent and measurable, with a clear statistical correlation. This confirms what doctors already suspected: severe weight loss from anorexia damages the liver. The additional finding that vitamin B12 levels track with both body weight and liver damage suggests that vitamin B12 might be a marker of overall nutritional status and organ damage in anorexia nervosa.

Previous research has shown that anorexia nervosa causes multiple organ problems, including liver dysfunction. However, the observation that vitamin B12 levels are frequently elevated in anorexia patients is relatively recent. This study adds to that emerging body of research by showing that these high vitamin B12 levels are not random—they appear to be connected to the severity of malnutrition and liver damage. This fits with the growing understanding that anorexia affects the body’s ability to process and store nutrients in complex ways.

Several important limitations should be considered. First, this was a retrospective study looking at past records, so researchers couldn’t control for all factors that might affect the results. Second, the study only included patients from one hospital in Japan, so the findings may not apply to all populations worldwide. Third, the study could not explain why vitamin B12 levels become so high—it only showed that they do. Fourth, the exact mechanisms connecting vitamin B12 to liver damage remain unclear. Finally, the study did not specify the exact number of patients included, which makes it harder to judge how reliable the findings are. The researchers acknowledge that more research is needed to understand these connections better.

The Bottom Line

Based on this research, doctors treating people with anorexia nervosa may want to consider measuring vitamin B12 levels as one additional tool (along with standard liver enzyme tests) to assess the severity of malnutrition and liver damage. However, this should not replace standard medical care or established diagnostic procedures. The confidence level for this recommendation is moderate, as the study shows an association but doesn’t prove cause-and-effect. Anyone with anorexia nervosa should work with a medical team that includes doctors, nutritionists, and mental health professionals.

This research is most relevant to doctors and healthcare providers treating people with anorexia nervosa, as it suggests a new tool for assessment. It’s also important for people with anorexia nervosa and their families to understand that multiple body systems are affected by severe malnutrition, including the liver. This research should not be used to self-diagnose or self-treat. People without anorexia nervosa should not be concerned about their vitamin B12 levels based on this research, as the findings are specific to people with eating disorders.

If someone with anorexia nervosa begins treatment and nutrition improves, changes in vitamin B12 levels and liver enzyme levels would likely take weeks to months to become noticeable. Recovery from anorexia is a long-term process, and organ damage takes time to heal. There is no quick fix, and realistic expectations are important for motivation and mental health during recovery.

Want to Apply This Research?

  • Users in recovery from anorexia nervosa could track their vitamin B12 levels and liver enzyme test results (AST and ALT) from regular blood work appointments, recording the dates and values to monitor trends over time as they recover
  • Work with your healthcare team to schedule regular blood tests to monitor vitamin B12 and liver enzyme levels. Use the app to set reminders for these appointments and to record results, helping you and your doctor track progress in recovery and nutritional status
  • Create a long-term tracking system that records blood test results every 3-6 months during recovery. Chart these values over time to visualize improvements as nutrition improves, which can provide motivation and concrete evidence of progress in recovery

This research describes associations found in medical records and does not prove cause-and-effect relationships. The findings are specific to people with anorexia nervosa and should not be applied to the general population. If you or someone you know is struggling with anorexia nervosa or another eating disorder, please seek professional medical help immediately. Anorexia nervosa is a serious psychiatric condition that requires comprehensive treatment including medical care, nutritional support, and mental health treatment. This article is for educational purposes only and should not replace professional medical advice. Always consult with qualified healthcare providers before making any health decisions.