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close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderObligatory nitrogen losses-adults
close this folderObligatory nitrogen losses of adult Thai males
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View the documentExperimental details
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View the documentConclusions and comments


Experimental details
Summary of main result
Conclusions and comments

Kraisid Toneisirin, Prapaisri P. Sirichakawal, and Aree Valyasevi
Faculty of Medicine, Ramathibodi Hospital and Institute of Nutrition, Mahidol University, Bangkok, Thailand


To determine the obligatory nitrogen losses in healthy adult Thai males.

Experimental details

1. Subjects
Four male adult Thais 21 to 25 years old. Their body weights were 45 to 67.5 kg, and their heights were 164.5 to 169 cm. They were healthy and well-nourished, based on medical history, physical examination, urinalysis, stool examination, chest x-ray, and a routine complete blood count.

2. Study Environment
The entire study was conducted at the clinical research ward (a metabolic unit) in

Ramathibodi Hospital. The climatic characteristics were those of tropical countries.

3. Physical Activity
The subjects were allowed to continue their usual activities but were not allowed to participate in competitive, active sports.

4. Duration of the Study
The study of obligatory nitrogen losses was carried out over a 14-day period.

TABLE 1. Composition of the Protein-Free Diet

Ingredients g/day
Mung bean starch 100.4
Mung bean noodles 100.0
Sugar 1 08.6
Margarine 48.0
Oil 30.0
Onion leaf 30.0
Wax gourd 27.0
Salt 5.1
Lemon juice 2.4
Soy sauce 2.0
Garlic 2.0
Carbonated beverage variable

5. Diets
The composition of the protein-free meal is shown in table 1. The subjects were given four meals per day at 7.30 a.m., 12 noon, 5.00 p.m., and 9.30 p.m. Daily energy intakes were constant, at about 45 kcal/kg/day. Fat provided approximately 30 per cent of the daily energy intake. Multivitamin and mineral tablets were given twice each day. Water was offered ad libitum but the volume was recorded daily.

6. Indicators and Measurements

  1. Total nitrogen in urine and faeces was measured by a calorimetric semi-automated procedure (Munro and Fleck, Mammalian Protein Metabolism, vol. 3 [1969]). Nitrogen balance was calculated from the last five and ten days of urinary and faecal nitrogen losses, respectively.
  2. Basal metabolic rate (BMR) was measured at seven-day intervals with a respirometer (closed circuit).
  3. Body weight was recorded daily.
  4. Serum concentrations of total protein, albumin, urea nitrogen, and some amino acids and amino transferase activities were measured at seven-day intervals.

TABLE 2. Obligatory Nitrogen Losses in Four Adult Thai Males

Subject U F S Total
M.P. 38.6 15.1 5 58.7
V.D. 32.5 12.4 5 49 9
S. R. 33.4 12.4 5 50.9
S.S. 35.0 10.6 5 50.6
Mean S.D. 34.9 2.7 12.6 1.9 5 10 52.5 4.2

U = urinary nitrogen losses, average from the last 5 days of 14-day dietary period.
F = faecal nitrogen losses, average from the last 10 days.
S = skin and other minor route nitrogen losses, taken from FAD/WHO.

Summary of main result

1. Daily Obligatory Nitrogen Losses in Four Adult Thai Males
Table 2 shows the data for obligatory nitrogen losses of the subjects. The means of urinary and faecal nitrogen losses were similar to most studies done in other countries. Total obligatory nitrogen losses were calculated after allowing 5 mg N/kg/day for skin and other minor losses.

2. Plasma Amino Acids
Table 3 shows that the concentration of valine decreased, while concentrations of alanine and glycine increased on days 7 and 14. The ratios of non-essential/essential amino acids (NEA/EA ratio) and of glycine/valine increased.

3. Other Measurements
Table 3 also shows that BMR and blood urea nitrogen (BUN) were lower and ALT was higher by day 7. By day 14, all indicators shown in the table differed from initial values.

TABLE 3. Blood Chemistry and Basal Metabolic Rates of Four Adult Thai Males Eating a Protein-Free Diet for 14 Days


Protein-free diet


Initial value

day 7

day 14

BMR (kcal/m/day)

1,134 94

927 261*

906 129*

Total protein (g/dl)

7.5 0.5

6.9 0.9

6.9 0.3*

Albumin (g/dl)

5.3 0.1

5.2 0.3

4.8 0.3*

BUN (mg/dl)

10.3 3.1

3.3 1.0*

2.7 0.7*

AST (sigma unit)

21.0 3.4

24.0 4.6

24.5 3.8*

ALT (sigma unit)

17.6 0.9

23.3 3.0*

24.0 0.9*

Valine (um/L)

258.5 7.7

175.1 30.8*

165.9 18.6*

Alanine (um/L)

219.8 61.4

696.9 225.4*

846.0 153.8*

Glycine (um/L)

299.7 39.7

468.3 15.0*

486.9 31.8*

NEA/EA ratio

2.2 0.1

3.4 0.5*

3.3 0.5*

Gly/Val ratio

1.2 0.1

2.7 0.4*

3.0 0.5*

* Differs from initial value p < 0.05.

Conclusions and comments

1. The results of obligatory nitrogen losses in this study of adult Thai males were quite similar to those that have been reported on 4 Indian men, on 13 men studied at the University of California, on 9 Nigerian men, and in 83 studies on MIT students and 50 Chinese studies on males. It seems, therefore, that the obligatory urinary and faecal nitrogen excretion of young men, expressed as mg/kg/day, does not differ among ethnic groups.

2. Factorial calculation of safe levels of protein intake, using a correction factor of 1.3 and adding another 30 per cent for individual variability, as suggested in 1973 by FAO/WHO, results in 0.56 g/kg/day, which is almost identical to the safe level of intake recommended by FAD/WHO. That recommendation has recently been questioned for populations at large or for long-term studies. Our own studies using multi-level nitrogen balance techniques indicate that 0.56 9 protein/kg/day is too low (see Tontisirin et al., this volume).


This study was supported by the research fund of the World Hunger Programme of the United Nations University. We would like to thank Dr. V. Tanphaichitr for medical care of the subjects, the staffs of the clinical research ward and food analysis laboratory, Ramathibodi Hospital, for their assistance, and the subjects who cooperated throughout the study.