Undernutrition, which affects nearly 800 million people worldwide, is a “potent accelerant” of the global tuberculosis epidemic, impacting disease incidence and treatment outcomes in infected patients, according to researchers.
According to the 2018 WHO Global Tuberculosis Report, the global TB burden is not shrinking fast enough to reach milestones set by the End TB Strategy, which aims to reduce TB deaths by 90% and new cases by 80% by 2030. To reach those targets, officials say case identification and treatment gaps must be closed and action must be taken to further understand TB.
“With the End TB Strategy, the global community has stepped forward for an endeavor that is, in several ways, more audacious and daring than sending a man to moon or ending the smallpox epidemic,” Pranay Sinha, MD, MPH, an infectious disease fellow at Boston University School of Medicine, told Infectious Disease News. “William Osler, the father of American medicine, once proclaimed that TB is ‘a social disease with a medical aspect.’ Even as we make epochal progress in our ability to diagnose and treat TB, our efforts to eliminate this ancient disease will fail if we don't consider the underlying social risk factors.
“Undernutrition is also the leading risk factor for TB and almost one in five cases of TB worldwide can be attributed to it. About 800 million individuals worldwide are undernourished due to a panoply of socioeconomic reasons. These unfortunate individuals are incredibly vulnerable to the ravages of the TB epidemic.”
Summarizing their review, Sinha and colleagues said the impact that undernutrition has on TB means addressing it will be a vital component of the End TB Strategy. They aimed to investigate its effect on immune response, vaccine response and TB incidence, severity and treatment outcomes.
“We felt it was important to write an integrative narrative review to refocus the attention of physicians, advocates, scientists and policymakers on undernutrition as we don't think the End TB strategy can redeem its pledge without addressing such a potent accelerant of the epidemic,” Sinha said.
A PubMed search of “tuberculosis and malnutrition” revealed 651 articles published between 2008 and 2018. Sinha and colleagues divided the review into three parts: impact of undernutrition on the adaptive and innate immune responses, the effect of vaccines in undernourished individuals, and the effect of undernutrition on the epidemiology of TB.
According to Sinha, the review produced numerous insights. For example, research shows that the effectiveness of novel vaccines against TB may be different in undernourished and well-nourished patients, underlining the need for a dedicated study as novel vaccines are developed. The review showed that nutritional supplementation has not been demonstrated to be effective in improving outcomes for TB patients. Sinha said a review of current literature showed that a handful of studies that have examined nutritional supplementation are heterogeneous and better powered studies are needed to address adequate caloric intake.
According to the researchers, although there are studies demonstrating the impact of undernutrition on immune defenses, much of the understanding of the subject comes from decades-old animal studies. They said there was “convincing evidence” in the literature that undernutrition is associated with TB incidence, and “strong evidence” for an association between undernutrition and poor TB outcomes.
“The End TB Strategy is counting largely on improved diagnostics and therapeutics as well as vaccine development to reduce global TB incidence and mortality,” Sinha said. “Our review suggests that undernutrition is an actionable risk factor for TB and has the potential of augmenting the decrease in TB incidence and mortality achieved through the End TB Strategy.”– by Caitlyn Stulpin
Disclosures: The authors report no relevant financial disclosures.