Pathways Linking Nutritional Status and Infectious Disease: Causal and Conceptual Frameworks

Abstract

It has been over 50 years since Scrimshaw and colleagues synthesized evidence that the overlap of malnutrition with infectious diseases within the same populations and individuals raised the likelihood that the two conditions interacted. Yet our understanding of causation remains incomplete, despite clear criteria for demonstrating some mechanisms of causality and despite a wealth of experimental and epidemiological studies. In this chapter, we present a framework that conceptualizes the various mechanisms by which host nutritional status might influence infections and/or microbial pathogenesis. The framework considers the impact of nutrition on exposure to the pathogen, the ability of the pathogen to establish in the host, and the ability of the pathogen to proliferate and spread to other hosts. It also considers influences of nutrition on the host responses and experience of infection including immunological responses, disease severity, and the effectiveness of drug interventions. The ways in which infection may change host nutritional status are also outlined. This framework provides a basis for interrogating the literature for observations that may be overlooked and for design of future studies.