A narrative review of recent progress in understanding the relationship between tuberculosis and protein energy malnutrition

European Journal of Clinical Nutrition (2013) 67, 1122–1128 & 2013 Macmillan Publishers Limited All rights reserved 0954-3007/13 www.nature.com/ejcn REVIEW A narrative review of recent progress in understanding the relationship between tuberculosis and protein energy malnutrition MLH Hood Protein energy malnutrition (PEM) and tuberculosis (TB) are the major public health issues, particularly in the developing country setting. Malnutrition is an underlying cause of many deaths and when left untreated devastates normal physical and cognitive development. TB continues to gather momentum as a serious infectious killer. They have both rightly been highlighted as important global health issues by their inclusion in the Millennium Development Goals. But what is known of their relationship with one another? It is historically accepted that PEM and TB have a synergistic relationship adversely having an impact on one another. However, researchers have sought to apply this understanding in an examination of the relationship between TB and PEM with often inconclusive results. This narrative review of recently published research and current knowledge may help delineate the association between PEM and TB mortality. Such results will assist future research in this important area of health—an area lacking evidence-based guidance. European Journal of Clinical Nutrition (2013) 67, 1122–1128; doi:10.1038/ejcn.2013.143; published online 14 August 2013 Keywords: protein energy malnutrition (PEM); protein calorie malnutrition; tuberculosis; review INTRODUCTION Despite increased attention in recent years and proven methods of treatment, tuberculosis (TB) and protein energy malnutrition (PEM) continue to be the major public health challenges in the developing country setting. TB remains second only to human immunodeficiency virus/ acquired immunodeficiency syndrome as the leading cause of death by a single infection worldwide.1 In 2010, TB reportedly killed 1.4 million people and had an estimated incidence of 8.8 million.2 Some reports approximate that one-third of the world’s population has an active or latent TB infection.2 This represents a huge public health priority, given the magnitude of potential future disease. Mycobacterium tuberculosis is the name of the bacillus that causes the TB disease.2 In most circumstances when the TB microbe is inhaled, the body’s cell-mediated immunity initiates an important protective response to TB. Among healthy individuals, this acquired immune response is very effective at containing the infection and rendering it latent.2 The predicament exists when immune-compromised individuals become actively ill with TB from either a recent exposure or the often imperceptible progression from a latent infection status.2 If left untreated, those with active TB will likely transmit the disease to others and will often die as a result of this disease or a related complication. PEM profoundly compromises immune function. PEM occurs as a result of insufficient protein, essential for creating and regenerating body tissue and calorie intake. The growth failure classification referring to PEM includes (i) acute malnutrition, the precursor to wasting and (ii) chronic malnutrition, which leads to stunting.3 Global rates of malnutrition, in its various forms, are difficult to measure. A recent report estimated that 925 million people, more than ever, are malnourished worldwide.4 Malnutrition is attributable to 42.6 million child deaths every year.5 It is widely accepted that a child with ongoing malnutrition will most certainly suffer from developmental impairment affecting their cognitive and physical abilities.6 Subsequently, their capacity as an adult will be suboptimal and will thereby negatively contribute to reduced household and state economies.6 Those suffering with malnutrition will also generally experience an increased susceptibility to illness and disease.5 Incidentally, when a fatality transpires, the cause of death is commonly credited to the acquired illness, and thus the role of malnutrition often slides under the radar.5 Malnutrition is a massive public health problem with far-reaching consequences. Important contributions to the understanding of TB and PEM within the literature have historically been recognised. Given the growing burden of these two health problems and their augmentation when combined, it is highly germane that further understanding and clarification be established. Despite the assertions of good nutrition being an important factor in the prophylaxis and treatment of TB, there remains no evidence-based guidance regarding nutritional regimes for individuals undergoing TB treatment.7 Thus, there is a need to identify and collate significant findings relating to this public health dilemma. This narrative review study aims to report on recent research that focuses on the synergistic relationship between TB and PEM, thereby providing a current reference for future clinical trials. The particular objectives of this review are: 1. To identify the trends/prevalence of PEM among those who present with TB; 2. to describe how PEM contributes to TB infection (susceptibility), disease progression and mortality; and 3. to determine whether macronutritional interventions targeted at individuals with PEM and TB are effective/justify further research. 1 Master of International Health Curtin University, Centre for International Health, Bentley, Western Australia, Australia. Correspondence: MLH Hood, Master of International Health Curtin University, 16 Arthur Street, Payneham, South Australia 5070, Australia. E-mail: Received 10 December 2012; revised 13 June 2013; accepted 6 July 2013; published online 14 August 2013 The relationship between TB and PEM MLH Hood 1123 Therefore, by helping establish research priorities, it is hoped that this study will assist in expediting the formation of best practice nutritional guidelines in the treatment of protein energy-malnourished TB patients. document were recorded. Table A1, Appendix 2 outlines the papers included in this review alongside their relevant findings. Thematic analysis of the data extraction forms, and corresponding papers where necessary, yielded several themes relevant to the study objectives, which are presented in the next section. MATERIALS AND METHODS Search strategy RESULTS Study characteristics Design and participants. Developing countries would benefit most from relevant research findings regarding the synergistic relationship between TB and PEM. Improvements in knowledge and interventional management would have greatest impact in such populations. Indeed, much of the primary research into the relationship between TB and PEM has been conducted in less developed regions in recent years. Of the 23 papers meeting the inclusion criteria for this review, 10 were recognised as narrative expert reviews—the United States producing six and four from the United Kingdom. Apart from the Republic of Korea (...truncated)