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close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderProtein requirements-adults, other protocols
close this folderProtein needs of young adult men fed common beans (phaseolus vulgaris) in combination with starch, plantain, maize, or rice
View the document(introduction...)
View the documentObjective
View the documentExperimental details
View the documentSummary of main results
View the documentConclusions and comments

Conclusions and comments

1. Larger amounts of beans are needed to obtain nitrogen equilibrium when they are eaten with starch or plantains than when they are eaten with cereal grains (see table 7). This is due both to the nitrogen contribution of the cereal grains and to the sulphur amino acids that they provide. The difference in the protein quality of the mixtures is demonstrated by the higher regression coefficients of the bean-andmaize or beanand-rice mixtures.

TABLE 4. Regression Equations between Nitrogen Intake and Nitrogen Retention of Subjects Fed Rice and Black Beans (Phaseolus vulgaris) in a 60:40 Protein Ratio

Subject a1 b1 Nitrogen intake for equilibrium (mg/kg/day) r
M.R. - 92.7 + 0.76 121.5 0.92
R.A. - 60.6 + 0.63 96.9 0.96
L.J. - 65.9 + 0.81 81.8 0.96
F.M. - 81.8 + 0.78 105.1 0.97
A.G. - 76.8 + 0.79 96.9 0.95
C.E. - 54.8 + 0.79 69.5 0.99
J.L. -54.5 + 0.55 98.8 0.98
G.P. - 70.1 +0.70 100.4 0.95
O.B. - 84.8 + 0.92 92.3 0.96
R.C. - 86.1 +0.87 98.6 0.92
Average -71.6 +0.75 95.6 0.87

1 NR-a+B(NI),

Protein digestibilities were low in the four studies, more so when the bean-and-plantain diet was used. The polyphenolic compounds in beans increase faecal nitrogen output.

Plantain also contains polyphenolic compounds that may add to the faecal nitrogen excretion.

2. More sulphur-containing amino acids are needed in the bean-paste diets eaten by populations who also consume starchy foods such as plantain or cassava. This does not seem to be so important in the diet of populations who consume cereal grains in addition to beans.

TABLE 5. Regression Equation between Nitrogen Intake and Nitrogen Retained of Subjects on a Diet of Plantains and Black Beans (Phaseolus vulgaris)

Subjects a1 b1 Nitrogen intake for equilibrium (mg/kg/day) r
11P-F.M. - 121.7 + 1.20 101.4 0.91
12P-O.B. - 54.0 + 0.47 114.9 0.82
13P-R.A. - 75.6 + 0.70 108.0 0.99
14P-S.P. - 66.9 + 0.53 126.2 0.76
15P-R.S. - 53.4 + 0.34 1 57.0 0.73
16P-O. B. --69.7 + 0.63 110.6 0.99
17P-H. R. - 109.8 + 0.92 119.3 0.92
18P-M.R. - 63.6 +0.29 219.3 0.87
19P-O.H. - 126.3 + 1.51 83.6 0.85
20P-N. Ro. - 75.3 + 0.64 117.6 0.96
Average -81.7 + 0.73 111.9 0.77

1 NR=a+b(NI).

TABLE 6. Nitrogen Intake for Nitrogen Equilibrium and Amounts of Foods Needed

Diet Nitrogen intake for nitrogen equilibrium (mg/kg/day)

Beans/day

Other food/day

dried wt. (g) cooked wt. (g) dried wt (g) cooked wt. (g)
Beans/starch 114 186 638 - -
Beans/plantain 112 185 636 - 855
Beans/maize 98 82 170 193 495
Beans/rice 95 52 194 281 802

TABLE 7. Apparent Protein Digestibility of Black Beans (Phaseolus vulgaris) Fed with Starchy Foods and Cereal Grains

Diet Nitrogen intake (mg/kg/day) Apparent protein digestibility (%)
Beans/starch 115.6 0.9 60.0 2.2
Beans/plantain 117.4 0.6 52.5 4.0
Beans/maize 127.6 0.5 61.0 9.0
Beans/rice 102.5 1.1 59.1 7.4