5. Key principles

The Nutrition Guidance Advisory Group agreed on five key guiding principles¹ that should be considered together with the evidence-informed recommendations. The principles are intended to inform and assist national technical groups, international and regional partners providing TB care, TB treatment services, and/or maternal and child health services in countries affected by TB, in formulating national or subnational nutritional recommendations.

Key principle 1. All people with active TB should receive TB diagnosis, treatment and care according to WHO guidelines and international standards of care

Appropriate diagnostic procedures, support for TB patients to complete treatment, and an appropriate combination of TB medications is crucial for curing the disease. The Stop TB Strategy provides the goals, objectives and indicators for TB care and control (68). The International Standards for Tuberculosis Care is a widely accepted level of care that all practitioners should achieve in managing patients who have TB (69). All essential elements of TB diagnosis and treatment should be provided free of charge to patients, in order to improve access to treatment and minimize the financial burden of the TB treatment on patients and households.

When undernutrition is identified at the time of TB diagnosis, TB should be considered a key causal factor that needs to be addressed. It is essential that nutrition assessment and assistance do not divert resources from optimal TB diagnosis and care.

Key principle 2. An adequate diet, containing all essential macro- and micronutrients, is necessary for the well-being and health of all people, including those with TB infection or TB disease

Consuming a well-balanced and adequate diet is key to maintaining optimal health and physical function at all ages. Nutritional status is an important determinant of resistance to infection and of general well-being. It is well established that nutritional deficiency is associated with impaired immunity. While malnutrition increases susceptibility to infection, infection can lead to metabolic stress and weight loss, further weakening immune function and nutritional status (13). Vitamins A, C, D, E, B 6 and folic acid and the minerals zinc, copper, selenium and iron all play key roles in metabolic pathways, cellular function and immune function. The concentration of these nutrients may have a role in an individual’s defence against TB (13, 70). Undernutrition is a strong contributor for active TB worldwide, and reduction in undernutrition in the general population could dramatically reduce the incidence of TB (11).

Key principle 3. Because of the clear bidirectional causal link between undernutrition and active TB, nutrition screening, assessment and management are integral components of TB treatment and care

Many people diagnosed with TB are undernourished at the time of diagnosis and nutrition intervention and care begin with a nutrition assessment.

Nutrition assessment (anthropometric,¹  biochemical,² clinical and dietary) is a prerequisite for the provision of good nutritional care. The results from screening and assessment inform counselling, which is usually done at the time of diagnosis and throughout treatment. Trained primary and lay health-care workers in primary and community health care can play an effective and integral role in nutrition screening and can identify patients affected by undernutrition and in need of further assessment.

At diagnosis, nutrition screening and assessment should include anthropometric and clinical measurements. If undernutrition is diagnosed, dietary assessment is also indicated. The following are required:

  • age-appropriate anthropometric measurements and classification of nutrition status (71–75):
  • height and weight:
  • in children who are less than 5 years of age, determination of weight-for-length or weight-for-height Z-score, using the WHO child growth standards (74)
  • in children and adolescents aged 5–19 years, determination of BMIfor-age-and-sex Z-score, using the WHO growth reference data for 5–19 years (15, 74)
  • in adults over 18 years of age, determination of BMI
  • mid-upper arm circumference:
  • in children who are less than 5 years of age and pregnant women
  • history of weight loss and signs of undernutrition, such as visible wasting or oedema
  • clinical assessment for comorbid conditions and concurrent treatments
  • diet assessment if nutritional status indicates malnutrition.

At TB follow-up, assessment should include, at a minimum:

  • anthropometric measures of weight, calculation of BMI and determination of weight and BMI change since diagnosis or last visit
  • classification of nutrition status (71–75).

In patients classified as having moderate undernutrition, or severe acute malnutrition, further risk factor and dietary assessment will be necessary, such as:

  • poor TB treatment adherence and/or response, resistance to TB drugs
  • clinical assessment for other non-dietary causes of malnutrition, including identification of important comorbidities like HIV, diabetes mellitus or alcohol or drug abuse
  • biochemical assessment where possible
  • dietary assessment, including assessment of food security.

Weight loss or failure to regain or maintain a healthy weight, at any stage of disease should trigger further assessment and appropriate interventions. Weight status is particularly important for people with MDR-TB, who require a very long duration of treatment and are more likely to require chronic care and palliative care.

The goal of nutrition counselling is to improve the dietary intake during recovery, to compensate for the increase in energy expenditure associated with recovery and weight regain; support the increase in cellular production and immune responses; support repair of damaged and diseased tissues (76); and manage the symptoms and side-effects of TB drugs, such as nausea and vomiting, anorexia, diarrhoea and altered taste.

Practical ways to meet macro- and micronutrient requirements through locally available and culturally appropriate foods should be provided.

Key principle 4Poverty and food insecurity are both causes and consequences of TB, and those involved in TB care therefore play an important role in recognizing and addressing these wider socioeconomic issues

Food insecurity, which is common in TB patients, and concomitant poor nutritional status, contribute to the global burden of active TB. As an integral part of TB care and control, the health sector should recognize and help address generalized malnutrition, food insecurity and other socioeconomic determinants and consequences of TB.

Food insecurity can contribute to poor access and adherence to TB treatment. Although evidence for the positive impact of food intervention on access and adherence to TB treatment is currently limited, interventions that address food security have the potential to improve access and adherence to TB treatment, as well as to support nutritional recovery through provision of nutritious foods. Such interventions can also help mitigate some of the financial and social consequences of TB. While food and nutrition are essential to the health and well-being of all individuals, food assistance may be neither the best or most appropriate enabler for access and adherence to TB treatment, nor the best way to alleviate the catastrophic economic and social costs of TB. It is important to consider the context. Where access and adherence are suboptimal, the causes, including food insecurity, can be assessed and addressed with a suitable package of enablers, which may include food assistance. The health sector and TB programmes can link with food security programmes and the social protection services to ensure that those with active TB, and their families, have access to existing systems for adequate food assistance and social benefits. TB programmes can assess and minimize unnecessary costs to the patient, in order to minimize the economic and social consequences for those affected.

Key principle 5. TB is commonly accompanied by comorbidities such as HIV, diabetes mellitus, smoking and alcohol or substance misuse, which have their own nutritional implications, and these should be fully considered during nutrition screening, assessment and counselling

Addressing comorbid conditions is of value not only for their potential contribution to nutritional status but also for improving access and response to TB treatment. Comorbid conditions should be considered as a part of a comprehensive clinical package for people with TB and/or undernutrition, the aim of which should be to improve general health and quality of life. Nutritional counselling, advice and support may have to be adjusted to the specific nutritional requirements of other comorbid conditions.

The immunosuppression associated with HIV has increased the incidence of active TB, especially in Africa where latent TB is common and HIV prevalence is high (19). HIV also increases the risk of reactivation of TB and the risk of undernutrition (19). Guidance is available for nutritional care and support for people living with HIV/AIDS (77). The increasing prevalence of diabetes mellitus in low- and middle-income countries is contributing to the sustained high incidence of TB disease. Diabetes mellitus triples the risk of developing TB and can worsen the clinical course of TB. TB can make management of blood glucose more difficult. Therefore, individuals with both TB and diabetes mellitus require careful clinical care. To optimize management of both diseases, TB must be diagnosed early in people with diabetes, and diabetes must be diagnosed early in people with TB (78). Diet is an important component of the management of diabetes mellitus and should be part of nutrition counselling of TB patients.

¹ A guiding principle in health is a rule that has to be followed, or that may be desirable to follow, and cannot be proved or contradicted, unless propositions are made that are even clearer. It is a comprehensive and fundamental law, doctrine, or assumption guiding health care and is understood by its users as the essential characteristic of health care and its designed purpose. A respect of the principles is needed in order for the health care to be used effectively. A guiding principle reflects a set of values that contextualize the provision of care in programmatic settings. Such values cannot be subjected to formal research but reflect preferences regarding public health approaches and goals. The principles are intended to inform and assist national technical groups and international and regional partners providing health care.

¹ Anthropometric measurements use measurements of the body to assess nutritional status.

² The most common nutritional biochemical assessments are for anaemia and serum albumin.

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