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close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderResearch papers: Protein requirements-adults, standard protocols
close this folderProtein requirements of young Chinese male adults for ordinary Chinese
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View the documentSummary of main results

Summary of main results

Table 4 and figures 1 and 2 show the nitrogen-balance data. All men were in negative nitrogen balance at an intake of 0.45 and 0.55 9 protein/kg in the mixed diets, and also at the 0.35 g level of egg protein/kg. At higher protein intakes, some subjects achieved positive nitrogen balance (figures 1 and 2).

The mean protein requirements for the mixed Chinese diet and the egg diet were 0.79 and 0.61 g/kg/day, respectively. The 97.5 per cent confidence limits for the requirements were calculated as 1.18 and 0.89 g/kg/day, respectively. The efficiency of utilization of the Chinese mixed dietary protein was 77 per cent that of the egg protein, based on relative nitrogen requirements.

TABLE 3. Composition of the Experimental Egg Diet

Ingredients (gm)

Levels of protein intake
(g/kg body wt/day)

  0.35 0.45 0.55
Whole egg 158 196 246
Cornstarch 296 270 260
Sugar 20 20 20
Soybean oil 41 36 30
Butter 30 30 30
Potassium phosphate 3 3 3
Calcium phosphate 3 3 3
Methyl-cellulose 6 6 6
Sodium chloride 10 10 10
Watermel on 200 200 200
Chinese cabbage 100 100 100
Mung bean noodles 200 200 200
Vitamin and mineral supplements2      
Nutrients: Protein (gm) 21 27 33
Fat (gm) 81.2 84 78.4
Carbohydrate (gm) 444 423 420.6
Calculated calories (kcal) 2,591 2,556 2,520

1 See footnote 1 in table 2.
2 See footnote 2 in table 2.

The actual energy intakes of the subjects in the two series of studies ranged from 38 to 46 kcal/kg. Most of the subjects spent a large part of their time in academic studies and their energy expenditure was light to moderate. When a body-weight increase of more than 0.2 kg or a decrease of more than 0.7 kg occurred, an adjustment in energy intake was made by subtraction or addition of soybean oil. Changes in body weight over the 56-day period ranged from -2.5 to +0.6 kg.

Conclusions and Comments

  1. The results obtained suggest that the 1973 FAD/WHO recommendation for young men of 0.57 9 egg protein/kg/day is inadequate. The recommended dietary allowance of protein estimated in 1972 for adults in Taiwan was 1.1 g/kg/day. That figure coincides with the present results using mixed Chinese diets.
  2. The NPU of a similar mixed Chinese diet was found to be 62 when weanling rats were used as the experimental animal. In contrast, the present study with young Chinese men showed the NPU of the mixed Chinese dietary protein to be only 43. The NPU of egg protein was 55 to 58 in the present study as compared with a value of 70 obtained in our earlier studies with infants.
  3. The mean nitrogen requirements of young Chinese men, based on regression analysis of the pooled data, are 127 mg (0.79 9) protein/kg/day with the mixed Chinese diet and 98 mg (0.61 9) protein/kg/day with the egg diet.

 

TABLE 4. Daily Nitrogen Balance Data1 with Chinese Mixed Diets and Egg Diets

Nitrogen intake Urinary nitrogen Faecal nitrogen Skin nitrogen Total nitrogen loss Nitrogen balance

(mg/kg body weight/day)

Chinese mixed diets

72.40.79 70.99.641 15.2+2.26 7.2+2.97 93.310.56 -20.9+10.30
87.91.03 77.910.47 16.9+2.20 8.77.37 103.611.81 -15.8+11.10
103.30.53 91.310.35 17.0+3.79 7.5+2.88 116.410.08 -12.510.14
121.00.87 99.0 9.12 16.7325 5.51.46 121.2 8.16 - 0.2 7.97

Egg diets

56.30.74 54.8+ 8.41 13.92.35 8.43.10 77.1 9.50 -20.8 9.11
71.70.78 63.9 9.76 13.1+2.39 10.54.28 87.4 8.56 -15.7 8.95
89.01.37 71.5 7.53 14.5+2.38 6.8+2.44 92.7 8.41 - 3.7 7.94

1 Mean S.D. of 15 subjects.



FIG.1 Daily Nitrogen Balance with Chinese Mixed Diet



FIG. 2. Daily Nitrogen Balance with Egg Diet

TABLE 5. Calculated Biological Value (BV), Net Protein Utilization (NPU), and True and Apparent Digestibility of the Test Dietary Proteins at Different Levels of Intake in Young Men

Level of protein intake BV1 NPU1

Digestibility

(g/kg/day)     Apparent True

Mixed diet

0.45 4713a,A 4513a,A 7g3c 973
0.55 4712a,A 4511a,A 813d,e 963
0.65 4210a,A 4010a,A 844c,d 963

Egg diet

0.35 sg17b 5818b 754f 984
0.45 5711b 5611b 823 982
0.55 5610b 5510b 843f 982

1 Mean +S.D. (n = 15).
a,b Same letters within a column are not significantly different.
A F ratio obtained from ANOVA test is significantly lower (P<0.01) than those in egg diet series.
c-f Group means within a column followed by the same letter are significantly different: c,e, p<0,01; d,f, p<0,05.