People who are gluten intolerant run four times the risk of developing active tuberculosis (TB) infection, suggests research published ahead of print in Thorax.
Gluten intolerance, or coeliac disease, is a chronic inflammatory condition of the small bowel, caused by an exaggerated immune response to the gluten found in wheat, barley, and rye.
It affects up to 1% of the population, and has been linked to several autoimmune diseases, as well as an increased likelihood of lymph gland cancer and complications of pregnancy.
The researchers analysed Swedish hospital discharge records from 1964 to 2003, looking for diagnoses of coeliac disease and TB.
During this period, more than 15,500 people were diagnosed with coeliac disease, almost a third of whom had been diagnosed as adults.
The final analysis was based on 14,335 people, who were compared with almost 70,000 other people, who were free of the disease.
A prior diagnosis of coeliac disease almost quadrupled the chances of active TB infection in both sexes, overall, while a diagnosis in childhood tripled the chances.
In a separate analysis, the researchers looked at the risk of subsequently developing coeliac disease after a diagnosis of TB in the same group of people.
This showed that a prior diagnosis of TB more than doubled the risks of coeliac disease.
The link between TB and gluten intolerance was not influenced by levels of poverty or deprivation with which TB is normally associated.
Poor intake of vitamin D and calcium in people with gluten intolerance as a result of both intestinal malabsorption and the nutritional deficiencies of a gluten free diet, may help to explain the findings, suggest the authors.
Vitamin D is a key player in marshalling the immune response against TB infection.