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Energy cost of communicable diseases in infancy and childhood

Abstract
1. Introduction
2. Variation in morbidity from infectious disease
3. Effects of infection on energy status

3.1. Anorexia
3.2. Decreased dietary thermogenesis
3.3. Cultural and therapeutic practices
3.4. Malabsorption
3.5. Metabolic effects
3.6. Fever
3.7. Additional intestinal loss
3.8. Anabolic responses during infection
3.9. Reduced growth and weight loss

4. Reduced activity
5. Energy requirements for recovery from infection
6. Anabolic response
References
Discussion (summarized by B. Schürch)

N.S. SCRIMSHAW *

* Massachusetts Institute of Technology, Cambridge, MA, and Food, Nutrition and Development Programme, United Nations University, Tokyo, Japan.

Abstract

The adverse effects of communicable disease on energy status result from decreased intakes due to anorexia and the tendance to withdraw solid foods, from decreased absorption when the gastrointestinal tract is affected, from increased metabolism due to fever, from increased catabolic losses due to the stress response, and from diversion of energy for the internal synthesis of globulins and other proteins in response to infection. Among underprivileged children in most developing countries, episodes of infectious disease are frequent, and their cumulative effects contribute significantly to impaired growth and development. Energy requirements for recovery, including catch-up growth, are accordingly increased, but they are spread over a longer period of time. Under developing country conditions there is a risk that the diet will be inadequate for rapid recovery, and that another infection will occur before recovery is complete.

1. Introduction

It is well known that infections, no matter how mild, affect both energy intakes and energy requirements through a number of mechanisms (SCRIMSHAW, TAYLOR and GORDON, 1968). In developing countries the presence of an infection is more likely than lack of available food to be responsible for undernutrition. This is equally true in a hospital situation in the United States. In both, however, the quantity and quality of food available to the individual is likely to be the limiting factor during the recovery period. At this time there is a period of increased appetite, and recovery is rapid if the diet is adequate.

The problem in generalizing about the magnitude of the effect of infection on energy requirements is that it depends on the nature, duration and severity of the infection for which the estimate is made. Moreover, for young children in developing country populations, it is not the effect of a single episode that is significant, but the pattern of frequent infections without full recovery between episodes. The failure to recover may be due either to an insufficient diet or to a new infection closely following the previous illness. The issue is complicated by the fact that a poorly nourished child is more likely to have frequent infections and to become still more malnourished as a result. Moreover, the same social and environmental circumstances that make malnutrition likely also increase the probability of frequent exposure to infection.

As summarized in Table 1, the potential effects of infection on energy requirements are variable and complex. Fever associated with an infection would increase energy expenditure while reduced physical activity would decrease it. Anecdotally and by personal observation, this does occur although quantitative documentation is lacking. In addition, even infections that are not associated with fever result in decreased food intake. They also cause a catabolic response that is particularly significant for protein requirements and contributes to energy depletion through this mechanism.

Table 1. Potential effects of infection on energy status

The challenge is to move beyond these conceptual and qualitative statements, to give some idea of the magnitude of the effect of infection on energy requirements under various conditions. Because the nature and circumstances surrounding each infectious episode are different, the relative significance of these effects and their cumulative impact on energy requirements will vary greatly.

2. Variation in morbidity from infectious disease

It is an epidemiological truism that disease morbidity varies with time, place, and person. All this means is that in some places infections may be highly prevalent and in others less so. Even within the same place, overall morbidity and the kinds of infections responsible change over time. Finally, there is great variability among individuals, even at the same time and place. The first step is to identify representative burdens of morbidity as a basis for estimating the effect of infection under any given set of circumstances.

Figures 1 to 3 from Guatemala (MATA, 1978), Mexico (CHAVEZ and MARTINEZ, 1982), and The Gambia (ECCLES et al., 1989), respectively, illustrate the high frequency of infections in young children under village conditions in developing countries. Table 2 provides evidence for the frequency of infections among infants in The Gambia. Each episode of infection is associated with adverse nutritional consequences ranging from mild to severe.

Table 2. Number of episodes of each illness and the number of days involved for 7 infants in rural Gambia