People with low levels of vitamin A living with individuals sick with tuberculosis (TB) may be 10 times more likely to develop the disease than people with high levels of the nutrient, new research has found.
The findings suggests that vitamin A supplementation might be an important part of controlling the spread of TB – one of the leading causes of death worldwide.
“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,” said senior author Megan Murray, professor at Harvard Medical School, at Boston in the US.
The findings, published in the journal Clinical Infectious Diseases, are based on an analysis of blood drawn from more than 6,000 household contacts of people diagnosed with TB in Lima, Peru. A 10-fold increase in risk is striking, the investigators said.
More than 1.8 million people died from TB in 2015. TB strikes hardest in low- and middle-income countries, where vitamin A deficiency can affect up to 30% of the population.
“It’s exciting to think that something as simple and inexpensive as supplementing people’s diets with vitamin A may be a powerful tool for preventing TB,” Murray said.
Vitamin A, also known as retinol, is best known among public health experts for its association with blindness. Healthy levels of the nutrient have been defined as those needed to prevent damage to eyesight.
Previous studies have suggested that vitamin A modulates the immune system and may ward off infection. However, just how vitamin A might affect the risk for TB has, up until now, remained unclear and a matter of debate.
In this study, the researchers found that the protective effect of vitamin A grew stronger as levels of the nutrient increased. Protection continued to grow well above what has been considered the minimum healthy level.
Vitamin A deficiency – defined as less than 200 micrograms per litre of blood – fuelled the risk of developing TB disease 10-fold. That risk was 20 times higher among young people between the ages of 10 and 19.
That finding, the researchers said, suggests that vitamin A may play an even greater role in immunity among younger people.