People with low levels of vitamin A are 10 times more likely to contract tuberculosis from those who are already infected with the disease, a new Harvard study has warned. Vitamin A supplementation might be an important part of controlling the spread of tuberculosis (TB) - one of the leading causes of death worldwide, researchers said. The team found that the protective effect of vitamin A grows stronger as levels of the nutrient increased. Vitamin A deficiency - defined as less than 200 micro grammes per litre of blood - fuelled the risk of developing TB disease 10-fold, researchers said. "This is one of the strongest risk factors reported in a large epidemiological study in years.
A 10-fold increase in risk is striking," said Megan Murray, Professor at Harvard University in the US. "If the link is affirmed in a clinical trial of vitamin A supplementation, it would make a powerful case for using this approach to prevent TB in people at high risk of disease," Murray said. Researchers analysed blood samples of about 6,000 participants who were household contacts of people suffering from TB. They found that of the 6,000 participants who agreed to have their blood analysed, 258 people developed TB. Among those, about 192 became sick with TB after enrolment in the study. Researchers then compared 180 blood samples obtained from people who developed TB disease during that time with blood samples obtained from household contacts who did not become sick. Participants were monitored regularly throughout the one-year follow-up for disease symptoms. They found that the risk was 20 times higher among young people between the ages of 10 and 19. The findings suggests that vitamin A may play an even greater role in immunity among younger people, researchers said. The study was published in the journal Clinical Infectious Diseases.