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| WHO/Marko Kokic |
By USAID (Adapted)
In Africa, tuberculosis (TB) is the most common
cause of death from a curable infectious disease. The nutritional consequences of
active TB are well recognized by clinicians, yet little is known about
effective nutritional management, nor of the interactions between TB treatment
and nutritional status. Many
patients with active TB experience severe weight loss and some show signs of vitamin
and mineral deficiencies. Persons with TB/HIV co-infection are even worse off
nutritionally. However, the evidence surrounding best practices for nutritional
management is very limited.
Generalized
malnutrition and TB
The association between TB and malnutrition has
long been known. TB makes malnutrition worse and malnutrition weakens immunity,
thereby increasing the likelihood that latent TB will develop into active disease.
Unfortunately, few studies have been designed to examine the relationship between
nutrition and the incidence of TB or its severity. It is very difficult to
determine accurately what the nutritional status of individuals with active TB
was before the onset of the disease, making it impossible to determine whether
malnutrition led to advancement of the disease or whether active TB led to
malnutrition. Several studies report that patients with active TB are more likely
to be wasted or have a lower body mass index (BMI = kg/m2) than healthy
controls and that wasting is associated with increased mortality in TB
patients.
TB affects protein metabolism and nutritional status
through multiple mechanisms. With anti-TB drug treatment, nutritional status usually
improves. This may be for a variety of reasons, including improved appetite and
food intake, reduced energy/nutrient demands, and improved metabolic efficiency.
However, most improvements are limited to increases in fat mass with little
effect on muscle tissue. The evidence suggests that adequate nutritional intake
during TB care and recovery is needed to fully restore nutritional status
during and following TB treatment and microbial cure. There are few published
studies on the optimum duration and effectiveness of nutritional support during
and following TB treatment.
HIV is one of the most important factors contributing
to the increase in active TB cases in sub-Saharan Africa. HIV infection increases
the risk of rapid TB disease progression. Co-infection with HIV and TB poses an
additional metabolic, physical, and nutritional burden, resulting in further increase
in energy expenditure, mal absorption, and micronutrient deficiency. There is evidence
that adults and children co-infected with HIV and TB are at greatest risk of malnutrition,
poor treatment outcomes, and death. Efforts to prevent, manage, and treat HIV
and TB have been largely separate endeavors, despite the overlapping epidemiology.
Continued and improved collaboration between TB and HIV/AIDS programs is
necessary to control TB more effectively among HIV-positive people and to make significant
public health gains.
Micronutrients
and TB
Reduced micronutrient intake, and especially intake
of vitamins and minerals such as vitamins A, E, and C, zinc, and selenium, has been
associated with an impaired immune response. There is evidence that at the time
of diagnosis, patients with active TB have depressed blood concentrations of
several micronutrients, including retinol, vitamins C and E, hemoglobin, zinc,
iron, and selenium compared with healthy controls—in part due to the immune
system response to infection. Anemia is commonly found in patients with pulmonary
TB and appears to be more common among TB/HIV co-infected patients. Data on the
impact of micronutrient supplementation on TB outcomes are limited. Studies
suggest, however, that daily supplementation may have an added benefit among
those who have deficiencies, especially during early months of anti-TB therapy.
Additional research is warranted on the impact of multiple micronutrient supplements
on TB-associated outcomes in settings where predominantly cereal-based local
diets are unlikely to provide adequate micronutrient content due to low
bioavailability and high fiber content.
Program
experience
Food assistance is a potentially influential means
for increasing adherence to TB treatment, reducing the costs to patients of
staying in treatment, and for improving nutritional status. Food assistance may
influence early case detection (encouraging patients to come sooner for
diagnosis and treatment), and promote completion of the full course of
treatment. Both are important to decrease TB transmission. Although most evidence
of the impact of food support on TB patients’ nutritional status, quality of
life, treatment adherence, and outcome is anecdotal, there is reason to believe
that such support will provide direct benefits to adults and children infected
with TB both during and following drug therapy. However, the cost to programs
of providing food support may be considerable. Other low-cost interventions,
such as periodic nutritional assessment, counseling on diet, nutritional
management of symptoms and drug side-effects, may help TB patient maintain or
increase their food intake and adhere to TB treatment. But again, program and/or
research evidence is limited.
Research
priorities
Many areas require further investigation to improve
our understanding and management of malnutrition in TB and TB/HIV co-infection.
Of particular priority are studies of the most effective approaches for treating
malnutrition and improving overall nutritional status and muscle mass in TB and
TB/HIV co-infected adults and children during and after TB treatment—taking into
consideration local diets and food availability. Successful and varied models for
integrating nutritional support into both TB and HIV/TB programs, and data on
the cost-effectiveness of integrated nutritional support, are also needed.
Source:
Executive summary. In: Nutrition and Tuberculosis: A review of the literatureand considerations for TB control programs. USAID, 2008.
More
information:
2008:
Nutrition and Tuberculosis: A review of the literature and considerations forTB control programs.
2013: Guideline: Nutritional care and support for patients with tuberculosis.
2013: Guideline: Nutritional care and support for patients with tuberculosis.
