This article critiques known studies in human populations and in relevant animal models to cover the in vivo evidence concerning the risk of TB due to malnutrition. Although TB is clearly related to malnutrition, the risk relative to specific levels and types of PEM and micronutrient deficiencies remain to be defined. Analysis of the NHANES-1 Epidemiological Follow-Up Study provides plausible estimates of the relative risk in a representative nationwide sample of adults. The 6- to 10-fold increase in relative risk includes mild to moderate as well as severe undernutrition. Severe PEM may increase the relative risk more than mild or moderate malnutrition, but severe malnutrition occurs in a small fraction of the population, even in low-income countries, except, for example, in famine, war, or disaster situations. Mild to moderate PEM or micronutrient deficiencies affect larger fractions of the population at risk for TB, so prevention efforts may not be successful if they target only severely undernourished groups.
The questions we would like answered include not only how much of the TB burden in a population is due to malnutrition but how is TB due to malnutrition? As suggested by work in the aerosol-infected guinea pig model, protein undernutrition in particular impairs host defense against TB and the impairment is rapidly reversed with nutritional rehabilitation. Changes in the movement and proliferation of T lymphocyte subpopulations in response to specific antigens, in the production of key cyto-kines, in the formation of organized granulomas, and in macrophage activation have been identified as important components of the process.
Was this article helpful?