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

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)

¹ NR=a+b(NI).

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

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