WASHINGTON - Family members who live with someone with tuberculosis may be shielded against the highly infectious disease by taking vitamin A. A new study finds that many of those who develop TB are deficient in the nutrient.
In a study of 6,000 people in Lima, Peru, researchers found that those whose diets were lacking in vitamin A had a 10-fold increased risk of developing TB from an infected family member. Young people, between the ages of 10 and 19, were found to have 20 times the risk of developing tuberculosis through close exposure to an infected loved one.
Researchers at Harvard Medical School found that having a vitamin A deficiency, common among some 30 percent of the world’s population in mostly developing nations, was a potent predictor of TB disease risk.
They said supplementing peoples’ diets with vitamin A may be a powerful tool for preventing TB.
Megan Murray of Harvard's Department of Global Health and Social Medicine said investigators followed the participants who lived with someone with TB for one year. All agreed to have their blood drawn at the start of the study.
Over the course of the investigation, Murray said 192 people of the 6,000 became sick. Their blood samples, taken at the beginning of the study, were compared to those of other close family members who did not have TB.
‘Really surprised’ by result
“And, in those blood samples, people who had gotten TB were much more likely to have been vitamin A deficient or to be in the lower two quartiles of vitamin A level, so not even technically vitamin A deficient, but just lower than ... people who didn’t get TB. ... And we were really surprised by that result because it wasn’t something we were expecting or looking for,” said Murray.
Murray said there’s scientific research that has shown the immune systems of people with vitamin A deficiency maybe negatively impacted, possibly making make them more susceptible to developing TB. The fact that more young people were at risk for tuberculosis infection, said researchers, suggested vitamin A may play an even greater role in the development of their immune systems.
But Murray was careful to stress her study did not establish a cause-and-effect relationship between vitamin A deficiency and development of tuberculosis.
Murray was asked whether it might be possible to shield close family members from tuberculosis by giving them vitamin A supplements if they are found to be deficient.
“The effect was so strong – as I say, it was so unexpected – that it does raise that question,” she replied.
Murray said the next step is to study whether adding vitamin A to antibiotics, given to family members of a loved one with TB, would offer additional protection against the disease.
Vitamin A deficiency is defined as less than 200 micrograms per liter of blood.
The findings were published in the journal Clinical Infectious Diseases. The U.S. National Institute of Allergy and Infectious Diseases funded the work.