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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 folderThe evaluation of soy protein isolate alone and in combination with fish in adult Japanese men
View the document(introduction...)
View the documentObjective
View the documentExperimental details
View the documentSummary of main results
View the documentConclusions

(introduction...)

Objective
Experimental details
Summary of main results
Conclusions

G. Inoue, T. Takahashi,* K. Kishi, T. Komatsu, and Y. Nilyama
Department of Nutrition, School of Medicine, Tokushima University, Tokushima, Japan, and *Institute of Health and Sport Science, Tsukuba University, Ibaraki-ken, Japan

Objective

The nutritive values of soy protein isolate (Supro 620, Ralston-Purina Co., St. Louis, Mo, USA) alone and mixed with fish were compared with that of fish protein.

Experimental details

1. Subjects
Twenty-one male university students served as the subjects in these three series of experiments. They lived in a metabolic ward of our laboratory throughout the experiment. During the study, they continued their daily routine activities but were not allowed to do any hard physical work. Characteristics of the students are shown in table 1.

2. Diets
Each subject was given, successively, four levels of low-protein diets. Protein sources were cod fish (as a standard) for eight subjects, a soybean protein isolate (Supro) for five subjects, and a 50:50 mixture of both for eight subjects. Among these, five men received both the cod and mixed protein diets (see table 1). The fish and Supro were prepared as paste products (kamaboko) and fed in equal amounts three times a day. An example of the diet composition is shown in tables 2 and 3.

Each experimental period consisted of one day on a protein-free diet and ten days

TABLE 1. Characteristics of the Subjects

  Subject Age (years) Ht. (cm) Wt (kg) Chest circumference (cm) Subscapular skin-fold (mm) BMR
(kcal/kg)
Blood pressure (mmHg)
Fish A 21 171 63.3 86.1 13.5 22.7 125/75
B 20 164 56.5 84.6 7.5 25.6 135/82
C 19 171 58.1 84.8 8.2 27.4 145/90
D 24 171 69.8 97.6 15.2 21.2 120/75
E 22 179 64.3 90.0 9.5 22.4 115/75
F 22 172 63.2 90.8 11.8 22.5 130/85
G 20 168 57.6 83.4 11.0 24.5 120/70
K 22 166 71.6 91.8 18.8 25.6 125/84
Mean 21 170 63.1 88.6 11.9 24.0 127 80
S.D. 2 5 5.6 4.8 3.8 2.1 10 7
Supro M 21 173 68.2 92.0 7.0    
N 21 161 53.9 87.4 8.0    
O 28 164 54.6 89.8 7.0    
P 22 164 74.0 92.7 12.0    
Q 26 174 77.5 99.8 14.0    
Mean 24 167 65.6 92.3 9.6    
S.D. 3 6 10.9 4.7 3.2    
Mixed A 21 171 63.4 84.9 15.3 21.7 105/70
B 21 164 59.2 86.7 7.5 21.9 133/92
C 20 170 59.4 85.1 7.8 24.2 148/93
D 24 171 68.3 98.3 15.0 24.8 118/75
E 22 178 62.3 88.5 8.5 25.9 122/83
H 25 170 60.3 87.8 8.5 23.2 95/58
I 21 166 52.0 83.4 6.0 27.3 108/72
J 21 168 61.0 85.7 10.5 25.9 117/83
Mean 22 170 60.7 87.6 9.9 24.4 118 77
S.D. 2 4 4.6 4.6 3.5 2.0 17 12

 

TABLE 2. Diet Composition (Example). Subject: 65 kg; mixed protein 0.55 g/kg; energy 45 kcal/kg.

Materials g/day
Cod kamaboko * 155
Supro kamaboko* 107.5
Sugar 323
Cornstarch 300
Margarine 32
Corn oil 30
Agar 3
Baking powder 5
Salt 2.5
Mineral mixture 6
Vitamin mixture 3

* For composition of the kamaboko, see table 3. The nitrogen contents are as follows: Dried cod 89.6 mg/g; dried Supro 147.2 mg/g; cod kamabako 18.45 mg/g; Supro kamaboko 26.6 mg/g. Nitrogen intake was 2.86 g/day equally in cod and Supro.

TABLE 3. Composition of Kamaboko Products

 

Cod

Supro

  Parts % Parts %
Cod paste 100 77.2 - -
Supro 620 - - 20 17.5
NaCI 3 2.3 3 2.6
Potato starch 5 3 9 5 4 4
Sugar 1.5 1.2 1.5 1.3
Water 20 15.4 85 74.2

Total 129.5 100.0 114.5 100.0 on the experimental diet, followed by three days on a free choice (ad libitum) diet. Four periods were included in the study, with 0.35, 0.45, 0.55, and 0.65 9 protein/ kg/day fed to each man in a random order. Energy intake was constant for each individual to maintain body weight (mean + S.D. = 44.6 + 2.4 kcal/kg; range = 38.4 to 49.8).

3. Measurements and Indicators

a. Anthropometry: body weight, height, arm and leg circumferences, skin-fold thickness.
b. Blood analyses: RBC and WBC count, haemoglobin, haematocrit.
c. Plasma analyses: total proteins (Biuret), albumin (dye-binding, HABCA), urea (indophenol colour reaction), glucose (Somogyi-Nelson), triglyceride (Van Handel), total cholesterol (Zak-Hanly), Na and K (atomic absorption), SGOT and SGPT (Reitman-Frankel). d. Urine analyses: urea (urease-indophenol), ammonia (phenol-hypochlorite), creatinine (Folin-Wu), uric acid (phosphotungstic acid), Na and K (atomic absorption).
e. Nitrogen balance: total nitrogen in diets, faeces, and urine was measured with a semi-micro-Kjeldahl technique during the last five days of each ten-day period on the experimental diets.

Summary of main results

1. Nitrogen Balance
See tables 4, 5, and 6 for individual data. Table 7 shows the individual and pooled regression equations of apparent nitrogen balance (i.e., without allowances for integumental and other insensible nitrogen losses) and nitrogen intake.

Figure 1 shows the individual variability and the upper 95 per cent confidence band for the pooled data of the fish-Supro mixture.

2. Relative Protein Quality of the Soybean Isolate
Based on the regression coefficients ("slope ratio"), nitrogen requirements for nitrogen balance ("maintenance intake"), and net protein utilization (NPU) shown in table 7, the quality of Supro 620 relative to cod fish was 82, 73, and 74 per cent, respectively (mean: 76 per cent). The fish-Supro mixture gave values of 115, 96, and 96 per cent, respectively, compared with fish alone.

3. Other Measurements
Anthropometric, blood, and urine indicators were not significantly affected by changes in dietary protein source.

TABLE 4. Summary of Nitrogen Balance Data for Young Men Given Different Levels of Fish Protein 1

Protein level Subject Body wt. (kg) Energy intake (kcal/kg)

Nitrogen balance (mg/kg)

Digestibility4 (%)
        Intake nitrogen Urinary nitrogen Faecal nitrogen Nitrogen balance  
0.35 g/kg/day A 64.0 44 3 55.2 48.6 10.2 - 8.6  
B 57.8 46.2 56.2 67.0 11.4 - 27.2  
C 58.0 42.0 56.0 54.1 12.1 - 15.2  
D5 _ _ _ _ _ _  
E 64.1 44.9 55.9 51.5 12.5 - 13.1  
F 63.7 47.5 55.4 62.2 14.9 - 26.7  
G 57.3 45.5 56.7 56.2 11.9 - 16.4  
K6 70.8 47.1 56.2 58,9 8.1 - 15.8  
Mean 60.8 45.1 55.9 56.6 12.2 - 17.9 100.0
S. D. 3 4 1.9 0.5 6.9 1.6 7.5  
0,45 g/kg/day A 63.7 45.5 71.3 61.2 10.5 - 5.4  
B 57.1 44.1 70.6 64.1 11.2 - 9.7  
C 57.8 42.1 72.3 64.9 13.7 - 11.3  
D 71.1 38.8 69.9 60.2 9.7 - 5.0  
E 65.1 44.2 70.8 61.9 12.1 - 8.2  
F 63.0 47.0 72.1 74.0 13.3 - 20.2  
G 57.9 45.1 72.2 64.8 11.2 - 8.8  
K6 71.3 47.8 71.8 86.6 8.8 - 28.6  
Mean 62.2 43.8 71.3 64.4 11,7 - 9.8 100.0
S.D. 5.1 2.7 0.9 4.6 1.5 5.1  
0,55 g/kg/day A 63.5 44.6 87.4 64.6 11.6 + 6.2  
B 57.5 46.6 87.3 72.2 11.1 - 1.0  
C5 - - - - - -  
D 70.3 39.3 86.3 73.5 8,7 - 0.9  
E 64.7 44.5 87.0 74.5 16.8 - 9.3  
F 63.2 46.9 87.7 78.2 15.2 - 10.7  
G 58.7 44.5 86.9 70.9 13.3 - 2.3  
K6 70.7 48.2 88.4 109,1 9.1 - 34.8  
Mean 63.0 44.4 87.1 72.3 12.9 - 3.0 99.4
S.D. 4.6 2.7 0.5 4.5 2.9 6.2  
0.65 g/kg/day A 64.5 43.7 103.1 80.6 12,9 + 4.6  
B 57.9 45.3 102.4 92.7 1 2.4 - 7.7  
C 58.6 41.6 102.9 84.8 13.0 + 0.1  
D 70.1 39.4 102.4 77.3 10.1 +10.0  
E 64.2 44.9 103.7 90.2 12.8 - 4.3  
F 63.6 44.6 103.0 89.5 14.9 - 6.4  
G 58.4 44.9 101.5 82.7 14.4 - 0.6  
K6 70.9 46.1 104.2 118.7 8.9 - 28.4  
Mean 62.3 43.5 102.7 84.5 1 2.9 - 0.6 99.5
S.D. 4.4 2.2 0.7 5.6 1.5 6.3  

1 Values are means for the last five days at each protein level.
2 Mean faecal nitrogen loss for the last eight days at each protein level,
3 True nitrogen balance was calculated using 5.0 mg N/kg as an estimate of miscellaneous losses.
4 True digestibility was calculated using 1 2.4 mg N/kg as faecal metabolic nitrogen,
5 The experiments of subject D in low-protein diet 1 and Subject C in low-protein diet 3 were interrupted because of febrile upper respiratory infections.
6 All data of subject K were omitted from further analyses because the nitrogen balance was inversely related to nitrogen intake.

TABLE 5. Summary of Nitrogen Balance Data for Young Men Given Different Levels of Supro 6201

Protein level Subject wt.² (kg)

Nitrogen balance (mg/kg)

Digestibility4 (%)
      Intake nitrogen Urinary nitrogen Faecal nitrogen Nitrogen balance  
0.35 g/kg/day M 68.2 56.0 67.7 7.0 - 23.8  
N 53.9 56.2 60.3 10.2 - 19.3  
O 54.6 55.9 68.1 11.4 - 28.6  
P 74.0 56.0 62.2 13.4 - 24.6  
Q 77 5 55.9 59.7 11.2 - 20.1  
Mean 65.6 56.0 63.6 10.6 -23.3 100.0
S.D. 10.9 0.1 4.0 2.3 3.8  
0.45 g/kg/day M 68.2 72.0 76.5 6.5 - 16.0  
N 53,9 72.0 73.5 8.7 - 15.2  
O 54.6 72.0 81.1 14.7 - 28.8  
P 74.0 72.2 69.7 10.4 - 13.0  
Q 77.0 72.0 74.2 12.5 - 19.7  
Mean 65.6 72.0 75.0 10.6 - 18.5 100.0
S.D. 10.9 0.1 4.2 3.2 6.2  
0.55 g/kg/day M 68.2 88.0 82.7 8.5 - 8.5  
N 53.9 88.1 84.2 11.9 - 13.0  
O 54.6 88.1 89.7 16.3 - 23.0  
P 74.0 88.0 85.4 11.9 - 14.3  
Q 77.5 88.1 88.0 12.1 - 17.0  
Mean 65.6 88.1 86.0 12.1 - 15.1 100.0
S.D. 10.9 0.1 2.8 2.8 5.4  
0.65 g/kg/day M 68.2 104.0 95.6 8.7 - 5.3  
N 53 9 103.9 97.2 10.6 - 8.9  
O 54.6 104.0 98.4 14.1 - 13.4  
P 74.0 104.1 90.5 14.3 - 5.8  
Q 77,5 104.1 93.3 15.1 - 9,3  
Mean 65.6 104.0 95.0 12.6 - 8.5 99.8
S.D. 10.9 0.1 3.2 2.8 3.3  

1 Energy intake: 45 ± 1 kcal/kg
2 Values ate means for the last five days at each protein level.
3 Mean faecal nitrogen loss for the last eight days at each protein level.
See footnotes for table 4.

TABLE 6. Summary of Nitrogen Balance Data for Young Men Given Different Levels of a Mixture Containing 50 per cent Fish Protein and 50 per cent Supro 6201

Protein level² Subject Body wt. (kg) Energy intake (kcal/kg)

Nitrogen balance (mg/kg)

Digestibility4 (%)
        Intake nitrogen Urinary nitrogen Faecal nitrogen Nitrogen balance  
0.35 g/kg/day A 62.9 44.1 56.1 57.2 14.1 - 20.2  
B 60.4 47.9 54.6 55.0 13.2 - 18.6  
C 69.5 44.6 55.5 69.2 12.9 - 31.6  
D 69.0 39A 55.2 46.8 9.3 - 5.9  
E 62.9 44.4 55.2 55.3 1 7.0 - 22.1  
H 60.2 44.9 55.8 56.0 13.6 - 18.8  
I 52.2 45.8 55.7 54.8 12.1 - 16.2  
J 60.4 46.7 56.6 56.0 10.8 - 15.2  
Mean 60.9 44.7 55.6 56.3 12.9 - 18.6 99.1
S.D. 4.7 2.5 0.6 6.1 2.3 7.2  
0.45 g/kg/day A 62.8 44.1 72.3 70.0 12.9 - 17.6  
B 58.7 48.2 72.4 73.3 13.8 - 19.7  
C 59.8 44.4 71.1 63.5 14.0 - 11,4  
D 68.6 39.7 71.4 61.7 9.6 - 4.9  
E 63.4 44.7 71.6 71.3 15.9 - 20.6  
H 60.6 44.6 71.3 65.0 14.4 - 13.1  
I 52.5 45.6 71.2 62.3 11.6 - 7.7  
J 60.9 46.1 70.9 71.3 11.3 - 16.7  
Mean 60.9 44.7 71.5 67.6 12.9 - 14,0 99.3
S.D. 4.6 2.4 0.5 4.0 2.0 5.7  
0,55 g/kg/day A 63.1 44,9 87.8 80.2 13.9 - 11,3  
B 59.2 49.8 87.7 89.2 14.9 - 21.4  
C 59.7 40.5 86.9 67.5 14.6 - 0.2  
D 69.0 38.4 86.7 69.3 8.7 + 3.7  
E 63.1 44.2 86.5 70.5 17.0 - 6.0  
H 60.8 44.4 86.8 70.4 16.3 - 4.9  
I 52.6 45.5 87.1 81.7 11.8 - 11.4  
J 61.2 45.1 86.3 85.6 12.4 - 16.7  
Mean 61.1 44.1 87.0 76.8 13.7 - 8.5 98.5
S.D. 4.6 3.4 0.5 8.4 2.7 8.3  
0.65 g/kg/day A 63.8 44.4 10.7 77.7 1 2.2 + 7.8-  
B 60.1 48.1 102.2 87.5 14.0 - 4.3  
C 59.7 44.5 102.8 91,1 14.2 - 7.5  
D 69.0 39.4 102.5 75.9 9.4 + 12.2  
E 62.8 45,4 102.7 76.6 1 5.4 + 5,7  
H 62.8 45.4 103.5 81.9 16.7 - 0.1  
I 52.7 45.4 102.6 76.5 13.3 + 7.8  
J 60.8 45.4 102.6 92.3 12.0 - 6.7  
Mean 61.2 44.7 102.7 82.4 13.4 + 1.9 99.0
S.D. 4.6 2.4 0.4 6.9 2.2 7.5  

1 Values are means for the lest five days at each protein level,
2 Each period consists of one day on protein-free diet and ten days on experimental diet,
3 Mean faacal nitrogen loss for the last eight days at each protein level,
4 True digestibility was calculated using 12,4 mg N/kg as faecal metabolic nitrogen.

TABLE 7. Summary of Maintenance Nitrogen and Equations Relating Nitrogen Balance to Nitrogen Intake

Individual data for apparent balance

Fish

Supro

Mixture

Subject Regression equation¹ Main- tenance² NPU Subject Regression equation Main- tenance NPU Subject Regression equation Main- tenance NPU
A Y= 0.320X-21.2 66.3 69.4 M Y= 0.396X-40.0 101.0 45.5 A Y = 0.577X-51.3 88.9 51.7
B Y=0.430X-40.4 94.0 49.0 N Y=0.210X-25.9 123.3 373 B Y=0.249X-30.8 123.7 37.2
C Y = 0.322X-29.4 88.6 50.9 O Y= 0.320X-44.1 137.8 33.4 C Y = 0.528X-49.4 93.6 49.2
D Y =0.416X-33.4 72.5 63.5 P Y= 0.345X-37.0 107.2 42.9 D Y= 0.399X-25.2 63.2 72.8
E Y = 0.158X-16.3 103.2 44.6 Q Y= 0.218X-29.0 133.0 34.6 E Y = 0.620X-54.7 88.2 52.1
F Y = 0.445X-46.4 104.3 44.1         H Y = 0.405X-36.3 89.6 51.3
G Y = 0.363X-30.8 84.8 54.2         I Y = 0.435X-36.3 83.4 55.1
Y=0.274X +0.03 - -         J Y=0.171X-22.3 130.4 35.3
Mean 0.357X 87.7 53.7 Mean 0.298X 120.5 38.7 Mean 0.423X 95.1 50.6
S.D. 0.105 14.5 9.6 S.D. 0.081 16.0 5.3 S.D. 0.155 21.8 11.5
C.V. 29.4 12.7 5.2 C.V. 27.3 19.3 2.0 C.V. 36.6 20.7 5.8


¹Y: Nitrogen balance (mg/kg), X: Nitrogen intake (mg/kg).
² Maintenance: Nitrogen intake for the maintenance of nitrogen equilibrium (mg/kg).
³ K: emitted from group analyses (see table 4).

Pooled data

Y=0.365X-31.8 Y=0.298X-35.2 Y=0.423X-38.3
Maintenance: 87.1±17.2 Maintenance: 118.1±15.4 Maintenance: 90.5±17.1
N = 26, r = +0.727 n = 20, r = +0.774 n = 32, r = +0.727






NPU = 52.8 NPU = 38.9 NPU = 50.8

Statistical analysis
Fish vs. Supro: t = 6.337, P < 0.01, significant
Fish vs. Mixture: t = 0.751, P > 0.10, not significant
Mixture vs. Supro:t = 5.877, P < 0.01, significant



FIG. 1. Relationship between Nitrogen Intake and Nitrogen Balance for the Mixed Protein of Fish and Supro 620

TABLE 8. Amino Acid Pattern Codfish and Soybean (Amino Acid Content of Foods, FAO, 1970)

  Nitrogen (g/100 9) Isoleu- cine Leucine Lysine Methionine Methionine - Cystine Phenyl-alanine PhenyI-alanine +
Tyrosine
Threonine Tryptophan Valine Total EAA
FAOIWHO reference (1973)   250 440 340 - (220)* - (380) 250 60 310 2,250
Codfish 2.72 293 533 626 211 (284) 316 (561) 323 70 327 3,017
Soybean 6.65 284 486 399 79 (162) 309 (505) 241 80 300 2,457
50% soy + 50%cod 4.68 289 510 513 145 (223) 313 (533) 282 75 314 2,737

*Numbers in parentheses are totals.

Conclusions

1. The mean intakes of fish protein, alone (87 mg N/kg/day) or mixed 50 per cent with Supro (91 mg N/kg/day), that were required to attain apparent nitrogen balance were similar to those previously reported by us for egg protein (90 mg N/kg/day) (Inoue et al., J. Nutr., 103: 1673 [1973] ±. However, the coefficient of variation for the mixture (22.9 per cent) was larger than that for fish (16.5 per cent) or egg (15.6 per cent).

2. The protein quality of Supro 620 was increased by mixing it with fish, probably because of complementation of sulphur-containing amino acids that resulted in a higher amino acid score (table 8). in Codfish and Soybean Foods, FAO, 1970)