Nutritional Requirements [Macro and Micro] in patients with Active TB

The nutritional requirements of TB patients can be considered in terms of their energy requirements, macronutrients (carbohydrates, protein, fats) and micronutrients (vitamins, minerals, and trace elements).
Energy requirements
The energy requirements of patients with active TB, varies with their age, gender, their activity levels as in persons without active TB. The requirements of energy in a patient with active TB can be divided into the energy requirements appropriate to their age, gender and activity levels, the additional requirements in view of the active TB disease, and the energy requirements for recovery of nutritional deficit. For estimation of the energy requirements patients with TB can be considered to be following a sedentary lifestyle, at least in the initial few months of treatment. The average requirement for energy for a sedentary adult is estimated to be 37 kcal/kg/day (man 39 kcal/kg/day and woman 35 kcal/kg/day). This calculation
assumes that the body weight is in the normal range. The additional requirements of energy in view of active TB disease are uncertain. A study in male patients with TB in India documented a 14% rise in their basal metabolic rate. Also, in patients with active HIV disease an additional energy
requirement of 10% has been recommended and we recommend the same in the case of patients with active TB. When this additional requirement is added to the average recommended intake, we arrive at a figure of approximately 40 calories/kg/body weight per day. Finally, we have to consider the energy requirements for recovery of nutritional deficit. This will vary between patients depending on the severity of wasting and undernutrition. In patients with active pulmonary TB in India, given the distribution of weights recorded in the programme, a significant proportion of patients are likely to have moderate to severe undernutrition. The goal of nutritional support would be to achieve nutritional recovery in these patients, so that the patients attain their target (desirable) body weight.

Note that these requirements above, are based on the actual body weight. Although there are rules of thumb to estimate the desirable/ideal body weight, this is best determined by a calculation of the weight which will correspond to the ideal BMI. WHO considers the range of BMI from 18.5- 24.9 kg/m² as normal. However, in developed countries, a BMI of 18.5 -20 is considered as marginal, while a BMI or more than 20 kg /m² is considered as adequate nutrition, as in the Malnutrition Universal Screening Tool. A WHO/FAO suggested an optimum median BMI at the population level of 21-23 kg/m². Based on these considerations we suggest that the minimum acceptable weight be the one which corresponds to the BMI of 18.5
kg/m² , which is the lower bound for the normal range of BMI. However, the desirable body weight would be the one which corresponds to the desirable/ideal BMI of 21 kg/m². A simplified field chart that allows health care providers to estimate the desirable body weight based on the measured height of the patient is mentioned in Annexure 9. This chart enables the estimation of the desirable body weight without the use of any calculation in field situation.
The box below offers an example of the calculation of the desirable body weight to be achieved by the end of treatment, and therefore an estimation of the amount of weight gain to be achieved during treatment. The median weights of Indian patients suggest that they have a weight of 10-20% on an average below the minimum acceptable or desirable, in those who are moderately undernourished. 

A weight gain of more than 5% of baseline body weight would be desirable in the first 2 months of therapy. In those with severe undernutrition, the loss of body weight is likely to be even higher. It would be desirable in the interests of early return to work that the weight and the lean body mass is regained in the first 2-4 months of therapy. We suggest therefore that a desirable rate of weight gain would be in the 2.5-5% per month in those with
moderate undernutrition and about 5% per month in those with severe undernutrition. In the example given in the box above, it would take about 2-3
months to regain body weight to a ‘minimum acceptable’ weight at the regain rate of 5% per month, or 5 months at a regain rate of 2.5%. For regaining a ‘desirable’ weight, it would take 5-6 months at the regain rate of 5% per month, or 10-12 months at a regain rate of 2.5%.
To achieve a weight gain of 1 kg, an excess of 7500 calories of intake over expenditure is required. To achieve a weight gain of 5-10 kg in the first 3-6 months, then an excess of around 37500-75000 calories over the patient’s expenditure, would be required in the first 3-6 months. For practical reasons, a single point estimate of the time required can be taken, this is an average value of 4 months; then, the additional energy requirement would be 312 -625 kCal/day, or 7-15 kCal/kg/day This would require an additional 312 -625 calories per day, over the usual recommended intake, which can be met with the additional nutritional support offered. Two important caveats are to be noted with this high intake: first, it may not be possible for a sick person to eat so much initially, and small frequent feeds should be tried while avoiding overenthusiastic feeding. The appetite of the patient provides
a good guide, and with its improvement with effective therapy in the initial phase, patients with severe undernutrition should be allowed to eat as much as they desire. Second, as recovery occurs, it is very important that patients do not remain completely sedentary and engage in some physical activity (such as house chores and walking) as tolerated, since it helps build muscle mass and excess fat deposition should be avoided in the regained weight.
Carbohydrate requirements
The proportion of carbohydrates in the diet recommended is 55-75% of total energy intake, and this is derived from intake of cereals, pulses, roots and tubers and vegetables. Carbohydrates are major sources of energy and patients can consume them during meals as well in snacks between meals to increase their energy intake. It is important to emphasize that the intake of complex carbohydrates (as found in low glycemic index foods) and adequate dietary fibre are essential.

Protein requirements
The requirements of protein would be 1.2-1.5 g/kg ideal body weight per day. The higher requirement of protein is in view of the metabolic stress related to the active infectious disease. Proteins should comprise around 10-15% of the total energy intake. A technical explanation for the calculation of the protein requirement is mentioned in Annexure 7 of the Guidance document to nutritional care and support for TB patients in India.
In the example quoted in Box 4.4 a daily protein intake of 51 -64 grams per day, would be required if we target the weight corresponding to the BMI of 18.5 kg/m². If we consider the desirable weight as 48.5 kg corresponding to the BMI of 21 kg/m², then the protein requirement would be in the range of 58-73 gms per day. Proteins in the diet can be of animal or plant origin. Proteins of animal origin like milk, eggs, and meat have relatively higher proportion of essential amino acids and are therefore considered as of higher biological value. However these may not be taken because of cultural, religious or economic considerations. Eggs have high quality protein and are cheaper than fish, meat. A mixture of vegetable proteins from
cereals and pulses is complimentary and can represent an adequate mix for dietary purposes in those who are vegetarian. True vegans who do not consume milk are uncommon in India, and milk and milk products can be also a good source of high biological value protein in vegetarians in India, who do consume these.
Fat requirements
These can comprise 15-30% of total daily energy intake. Fats are present in oils, nuts, milk and milk products, meat. Most cereals and pulses have low fat concentrations, except bajra and Bengal gram (around 5%). Groundnuts have around 40 percent fat, apart from being a good source of protein.
Fats and oils are dense in calories as each gram yields 9 kcal. In patients with reduced intakes like patients with TB, the addition of oil, ghee and nuts to the diet can help achieve the goals of energy intake.
Micronutrients
The recommended daily allowances of vitamins, minerals for Indians has been determined. These daily allowances can be obtained if the patient has an diet adequate in quantity and quality, with recommended intakes of the basic food groups- cereals and pulses; vegetables and fruits; milk or eggs or meat; oils, fats, nuts. However nutritional surveys have shown that in the general population, the intake of some of these ingredients of a balanced diet are suboptimal in India especially pulses, fruits, milk. These deficits are likely to be even commoner in TB patients who have reduced appetites, and are also likely to be poor.

We recommend that provision of 1 RDA of micronutrients as a supplement in view of the micronutrient deficiencies present in TB patients, their anorexia as well as the likelihood of limited food diversity. The approximate quantities of these micronutrients is mentioned in Annexure 8. There is no evidence that TB patients benefit from mega-doses of any micronutrients. We recommend screening of TB patients for the presence of anemia, which is very common in these patients as mentioned earlier. Iron and folic acid tablets can be added to the micronutrient supplement after 2 weeks of starting Anti-TB therapy.
Nutritional requirements in pregnant and lactating women with TB
Pregnant and lactating women have additional requirements of energy, proteins, folic acid, calcium and iron, in addition to the enhanced  requirements related to active disease and nutritional recovery. Pregnant women need an additional 300 cal, 15 g protein, 400 micrograms of folic acid, 1000 mg of calcium and 38 mg of iron per day.
Lactating women require about 400-550 extra calories per day, 18-25 g additional protein, additional amounts of vitamin A.

Resources

• Guidance document nutritional care and support for TB patients in India

Assessment