People being treated for eating disorders such as anorexia nervosa, bulimia nervosa, and binge eating appear to be at increased risk for autoimmune disorders including chronic gasteroenterological, ocular, dermatological, connective tissue, neurological, and hematological autoimmune conditions, according to a new study from Helsinki University.
Previous studies have documented an association between eating disorders and Type 1 Diabetes; this new study, however, expands this line of inquiry to include several different autoimmune conditions.
Anu Raevuori, MD, PhD, and her team compared over 2,300 patients receiving treatment at Helsinki University Hospital's Eating Disorder Unit to over 9,000 of their peers who did not have eating disorders.
They found that the risk of prior autoimmune disease in patients with eating disorders was significantly higher than in the controls. The lifetime prevalence of an autoimmune condition in those with eating disorders was 8.9%, compared to 5.4% in the control group.
This was not just related to gastrointestinal conditions such as Crohn's, or to endocrine conditions like Type 1 Diabetes. When the researchers removed subjects with the aforementioned digestive and endocrine disorders, they still found a higher prevalence of other autoimmune diseases among those with eating disorders.
This association held even after exclusion of all gastroenterological and endocrinological autoimmune conditions (Raevuori A, et al. PLoS ONE 9(8): e104845. doi:10.1371/journal.pone.0104845).
A Microbiome Connection?
The observed link between autoimmune and eating disorders opens the important question of whether or not immune-mediated mechanisms play a role in the onset and development of eating disorders.
According to Dr. Raevuori, it is unclear whether having an eating disorder contributes to an increased risk for developing autoimmune disease or vice versa, or if there is a common underlying etiology for both. The new study supports previous findings that people with autoimmune conditions and eating disorders show autoantibodies against peptides involved in regulation of appetite, stress, and emotional respsonsiveness.
The available data suggest that pro-inflammatory cytokines and autoantibodies may affect neurological function. It is still unclear, however, if changes in cytokines are caused by eating disorders or are due to still undiscovered underlying factors.
Dr. Raevuori's group has postulated that disruptions in the intestinal microbiome may contribute to the development of these auto-antibodies, and may explain the link between the gastrointestinal tract and the brain.
Healthy diversity and balance in the gut microbiome is important in the regulation of proper immune function; disturbances in either have been linked to autoimmune diseases and immune-mediated diseases such as allergies and Type 1 Diabetes (for more on the microbiome-brain connection, read: Welcome to the Microbiome—Holistic Medicine's New Frontier).
Generally, disordered food intake and excessive stress associated with eating disorders can disrupt microbiome homeostasis and alter gut flora composition. Specifically, anorexia nervosa patients have shown different microbiome composition compared to healthy and obese individuals. With bulimia nervosa, purging and excessive laxative use may damage the intestinal lining, leading to increased intestinal permeability, which may also contribute to autoimmune conditions.
Be on the Lookout
Although the specific etiology connecting autoimmune conditions and eating disorders is still unclear, this research holds important clinical implications.
If a patient is being evaluated or treated for an autoimmune disorder, it certainly makes sense to investigate the possibility of a concurrent eating disorder. Similarly, look for symptoms of autoimmune conditions in patients with eating disorders.
Dr. Raevuori's study was unfortunately not able to explore the effect of gender, owing to a low number of males in the cohorts.
She explains that cultural and biological factors contributing to the etiology of eating disorders are not mutually exclusive. The two types of influences work together to bring about the development of an eating disorder.
Typically, males require more risk factors in order to develop an eating disorder than females. Her study did find that males with bulimia nervosa were significantly more likely to have an autoimmune disease when compared to females with bulimia nervosa.
Further exploration into the etiology and the specific mechanisms linking eating disorders and autoimmune disease may also help in the development of better preventative and therapeutic measures in the future.