WASHINGTON, DC – Malnutrition is a significant risk factor for developing active tuberculosis disease, accounting for one quarter of all 1.6 million tuberculosis cases globally, while other risk factors like smoking and diabetes are attributed with 16% and 7.5% of infections respectively, researchers said here Tuesday.
In spite of that, Dr. Natasha Hochberg of Boston Medical Center said, the World Health Organization does not provide recommendations on addressing poor nutrition as a risk factor for acquiring tuberculosis infection, and discussions on improving nutrition among those most at risk are largely left out of TB elimination efforts.
Poor nutrition, particularly the lack of a protein-sufficient diet, weakens the immune system and increases the risk of acquiring infections while decreasing the body’s ability to clear infections, Hochberg said. “Undernutrition hits a lot of pathways we need to control TB,” ultimately increasing the severity of TB illness, she said.
Multiple surveys have shown a relationship between too-low body mass index – or BMI – that puts individuals in the underweight range, and higher incidence of TB, Hochberg said, including a country-wide survey of 1.7 million people in Norway which showed incidence of TB is higher among people with low BMI compared to those with higher BMI. A National Health and Nutrition Examination Survey in the U.S. found individuals with low BMI were 12.4 times more likely to develop TB than those with normal BMI, Hochberg said.
“For every unit increase in BMI,” Hochberg said, “there is almost a 14 percent decrease in risk for TB.”
Hochberg further illustrated the relationship between undernutrition and TB incidence by showing a map highlighting high TB-burden countries and countries with high levels of malnutrition – the maps were nearly the same.
Nowhere is the link between malnutrition and TB infection more apparent than in India, home to 27% of TB infections globally and where one-third of adults and 21% of children are underweight. Among Indian children, 35% younger than five are stunted due to poor nutrition.
“Stunting is irreversible,” Hochberg said. “It happens in many areas where we see the highest burdens of TB,” she said.
Malnutrition impacts the severity of illness and treatment outcomes, Hochberg said. A study of multidrug-resistant TB patients in Latvia showed patients who were severely malnourished had more extensive lung damage, while another study found severely malnourished TB patients in Ethiopia were more likely to die during the course of treatment, she said.
Malnutrition also impacts the ability to detect TB infection, Hochberg said. In a study examining TB infection among household contacts of people with active disease, researchers found severely malnourished children who were household contacts were more likely to have a negative tuberculin skin test, and another study showed individuals with lower BMI were more likely to have a negative quantiferon test for latent TB infection.
Providing nutritional support along with TB treatment helps to improve outcomes, Hochberg said, particularly if patients gain five percent of their body weigh in the first two months of treatment. However, researchers have found that many patients who receive nutritional supplementation end up sharing food with other low-income family members rather than consuming it themselves.
A possible solution to this problem is currently being tested in India, Hochberg said, where the TB Learning the Impact of Nutrition – or TB LION – study is enrolling malnourished TB patients and their well-nourished roommates and providing nutritional support for the entire household.
“Giving families of patients high protein foods that are culturally acceptable is a sustainable intervention,” Hochberg said.
“We need to incorporate nutritional interventions along with optimizing the use of existing tools and developing new ones to achieve TB elimination goals,” she said.