Nutrient partitioning in tuberculosis

Nutrition Research Newsletter, August, 2004

Tuberculosis (TB) is still the most frequent cause of wasting worldwide. However, the pathophysiology of wasting in TB remains poorly understood, in contrast with the information related to HIV-associated wasting. Although antimycobacterial treatment of TB is highly successful, many patient remain underweight after six months of treatment.

The relative distribution of nutrient loss or gain between fat and protein stores is called nutrient partitioning. During starvation and refeeding, nutrient partitioning varies widely among individuals but is a stable intraindividual trait. Since the functional consequences of wasting and recovery may depend on the distribution of lost and gained nutrient stores between protein and fat masses, a group of British researches studied nutrient partitioning in patients with pulmonary TB receiving standard antimycobacterial treatment.

Body composition measures and immune response were taken of 21 men and 9 women with pulmonary TB and free of concomitant diseases at baseline and after one and six months of treatment. All subjects underwent dual-energy X-ray absorptiometry and deuterium bromide dilution tests, and a four-compartment model of FM, total body water (TBW), bone minerals (BM) and protein mass (PM) was derived. The ratio of PM to FM was expressed as the energy content (p-ratio). Changes in the p-ratio were related to disease severity as measured by radiologic criteria.

From baseline to month 6, the patients gained 9.5% in body weight, which was mainly due to 43.6% gain in FM, in contrast with a lack of significant change in PM. No significant changes in TBW, extracellular water (ECW) or intracellular water (ICW) were observed. Results were similar in men and women. The p-ratio decreased from baseline to month 1 and then declined further by month 6. Changes in weight from baseline to month 6 were strongly correlated with changes in FM but not with changes in PM and no correlation between changes in FM and PM was found.

The data from the current study show that clinical recovery in patients with pulmonary TB does not guarantee the restoration of body protein, despite marked weight gain in most patients. These findings confirm and extend prior reports about preferential fat storage during recovery from catabolic illness, such as after critical care and in HIV infection. Predominant fat accumulation persisted until the end of antituberculosis treatment at six months, consistent with an ongoing anabolic block.

Achim Schwenk, Lisa Hodgson, Antony Wright, et al., Nutrient partitioning during treatment of tuberculosis: gain in body fat mass but not in protein mass, Am J Clin Nutr 79:1006-10012 (June 2004) [Address reprint requests to A Schwenk, Consultant in HIV Medicine-Coleridge Unit, North Middlesex University Hospital, Sterling Way, London N18 1QX, United Kingdom. E-mail: a.schwenk@doctors.org.uk]