Cover Image
close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderObligatory and integumental nitrogen losses - children
close this folderObligatory nitrogen losses and factorial calculations of protein requirements of pre-school children
View the document(introduction...)
View the documentObjectives
View the documentExperimental details
View the documentSummary of the main results
View the documentConclusions

(introduction...)

Objectives
Experimental details
Summary of the main results
Conclusions

BenjamTord Fernando E. Viteri
Institute of Nutrition of Central America and Panama (INCAP), Guatemala City, Guatemala

Objectives

1. Measurement of obligatory faecal and urinary nitrogen excretion in children two years old or a little older.
2. Calculation of such children's protein requirements following the factorial nitrogen approach.

Experimental details

1. Subjects

a. Five children, all males, of mixed Maya and Caucasian descent (Lading).
b. Chronological age: 24 5 months (range: 17 to 31). Height-age: 16 5 months (range: 10 to 23).
c. All had been treated for severe, oedematous protein-energy malnutrition (kwashiorkor and marasmickwashiorkorl. They had recovered fully at least one month before beginning the studies, based on clinical, anthropometric, and biochemical criteria (plasma proteins, non-essential/essential amino acid ratio, haematological indices, urinary creatinine excretion, and creatinine-height index [CHI] ).
d. Weight: 10.66 1.14 kg (range: 8.82 to 11.96). Height: 79.8 4.9 cm (range: 72.9 to 86.4). Weight-for-height, percentage of expected: 98 1 per cent (range: 96 to 100 per cent). CHI: 0.95 0.07 (range: 0.89 to 1.04).
e. Intestinal parasites: Two children had asymptomatic giardiasis. One of them also had a light infestation with Trichuris trichiura (one or two eggs per microscopic slide preparation). They were not treated before the study.
f. All children were healthy throughout the study.

2. Study Environment
INCAP's Clinical Centre in Guatemala City, 1,500 m above sea level. Temperature: 18 to 24 C. Relative humidity: 40 to 50 per cent.

3. Physical Activity
Since no child had diarrhoea and defecation habits were known by the nurses, the children were confined to metabolic beds only part of the day. During most of the day they moved freely in the Clinical Centre and outdoor playing grounds wearing urine-collection bags, except for those children who were toilet-trained. They participated in games that involved climbing ramps, walking uphill, and tossing balls.

4. Duration of the Study
Four children were studied simultaneously for nine days. A fifth child was studied five months later for seven days.

5. Diet

  1. A nitrogen-free, liquid formula was prepared with the following ingredients (g/kg/day): cornstarch 2.5; sugar 15.2; cottonseed oil 3.3; mineral mixture (NaCI, KCI, Na2HPO4, CaCO3, mg SO4) 0.6; water to make a final weight of 80 g/kg/day.
  2. The liquid formulas were cooked for 10 to 20 minutes. They were free of fibre, and vegetable oil provided 30 per cent of the energy.
  3. The diet, which provided 100 kcal/kg/day, was divided into five isoenergetic meals and fed at threehour intervals. It was supplemented with vitamins, iron, iodine, zinc, and manganese. Additional water was offered ad libitum.
  4. Prior to the study, the children consumed milk-based liquid formulas for several days.

6. Indicators and Measurements

  1. Urine was collected at 23- to 25-hour intervals, and the volume was corrected mathematically to correspond to a 24-hour period. Faeces were not collected during the first day of the study. Beginning on the second day, carmine red and brilliant blue were given alternately as markers with breakfast every two days. Faeces were collected between markers as 48-hour pools. They were dried at 80 C and homogenized.
  2. Urinary and faecal aliquots were digested, and their nitrogen contents were determined by a microKjeldahl technique using selenium (Se) as a catalyst. Diet aliquots were analysed in the same way to ensure the absence of nitrogen. Tryptophan standards were analysed simultaneously.
  3. Body weight was measured daily before breakfast.

Summary of the main results

1. Obligatory Nitrogen Losses
The results are summarized in table 1 and figure 1. The mean and S.D. for the combined data of days five to nine were 34.0 5.3, 19.5 6.9, and 53.7 8.1 mg N/ kg/day for urinary, faecal, and both urinary and faecal nitrogen, respectively.

If the study had been done in only six days and the mean values of days five and six used, the corresponding results would have been 33.2 5.9, 19.9 6.8, and 53.0 7.7 mg N/kg/day for urinary, faecal, and both urinary and faecal nitrogen, respectively.

2. Factorial Calculations
Assuming that integumental nitrogen losses were of the order of 5 mg N/kg/day on a protein-free diet, total obligatory nitrogen losses would be 59 mg/kg/day, or 40 per cent less than the current FAD/WHO estimates. Adding 15 mg N/kg/day for growth of children of the same height-age and multiplying by 1.3, as suggested by FAD/WHO (WHO Tech. Rep. Ser. No. 522, 1973), results in an estimated mean requirement of 96.2 mg N/kg/day, equivalent to 0.60 9 of milk or egg protein/kg/day. This value coincides with the mean requirement of 0.61 g/kg/day calculated by us using multiple-level nitrogen balance techniques (see summary of study by Torabrera Santiago, and Viteri, this volume).

Conclusions

1. The obligatory faecal and urinary nitrogen excretion on a protein-free, low-residue diet can be assessed during the last two of six experimental days.

2. Urinary and faecal nitrogen are 34 5 and 20 7 mg N/kg/day, respectively.

Child

Days on a nitrogen - free diet

 

1

2

3

4

5

6

7

8

9

Urinary nitrogen

58.9

28,9

41.0

37 4

25 5

33.6

27,4

31.3

44.2

C.R.

58.9

28.9

41.0

37.4

25,5

33.6

27,4

31,3

30 2

W.M.

81.3

52.4

29.8

39.0

31.2

33.4

35.2

34.0

30.2

I.G.

85.4

39.0

37.1

33.6

31.1

39.8

34.3

39.4

33.3

H.A.

89.4

68.6

60.8

43.4

40.8

38.4

39.8

31.1

40.3

A.A.

-

58.2

36.9

39.9

22.8

.5.5

29.2

-

-

Mean

78.8

49.4

41.1

38.6

30.2

36.1

33.2

33.9

37.0

S.D.

11.8

15.8

11.8

3.6

6.9

2.8

4.9

3.4

6.0

Faecal nitrogen  
C R.a  

19.8

 

26,3

 

27,9

 

28.2

 
W.M. a,b  

19.0

 

23.1

 

20.1

 

13,9

 
I.G.  

9.7

 

7.4

 

15.2

 

9.7

 
H.A.  

29.7

 

12.1

 

27.2

 

22.1

 
A.A.  

12.9

 

22.0

 

17.9

 

-

 
Mean  

18.2

 

18.1

 

21.6

 

18.5

 
S.D.  

7.7

 

8.0

 

5.7

 

8.3

 
Total (urinary + faecal nitrogen)  
Mean -  

67.6

59.3

56.7

48.4

57.7

54.8

52.4

55.5

S.D. -  

20.5

18.4

9.4

6.8

5.8

7.3

5.2

14.4

a Giardia lamblia in stools.
b Trichuris trichiura in stools. Both parasites diagnosed in faecal specimens collected four to nine weeks before the study.



FIG. 1. Urinary and Faecal Nitrogen Excretion on a Nitrogen-Free Diet

3. The mild parasitic infestations in two of the five children did not increase faecal nitrogen.

4. Factorial calculations using the empirical correction factor of 30 per cent support the conclusions of our studies with milk protein.