The utilization of proteins and amino acids in diets based on cassava (Manihot utilissima), rice or sorghum (Sorghum sativa) by young Nigerian men of low income.

I. The net protein utilization (NPU, the percentage of dietary nitrogen retained in the body, allowance being made for endogenous urinary and faecal N) of diets composed of Nigerian foodstuffs, based on rice, sorghum (Sorghum sutiva) or cassava (Manihot utilissima), was compared to that of a minimal protein diet used to determine endogenous N excretion, supplemented with whole egg. The addition of DL-methionine and L-tryptophan to the rice diet produced a small but non-significant increase in NPU, whereas the addition of DL-methionine to the cassava diet produced a very significant increase in NPU. The NPU of a diet based on home-pounded, winnowed, sorghum flour was higher than that of a diet based on milled whole-meal sorghum due to the low digestibility of the latter diet. 2. The digestibility of the rice and cassava diets were the same, although the total crude fibre content of the rice diets was lower than that of the cassava diets. 3. Nigerian men used the proteins of the egg diet and of mixed diets based on rice, sorghum and cassava more efficiently than predicted by applying methods recommended by the FAO/WHO ad hoc Expert Committee on Energy and Protein Requirements (FAO/WHO, 1973). 4. The recommendations of that Committee (FAO/WHO, 1973) to reduce the amounts of sulphur amino acids and tryptophan, contained in the 'provisional pattern of amino acids' proposed by the F A 0 Committee on Protein Requirements (FAO, 1957)~ are supported, but the increases in lysine and threonine are not supported, by the present results. The similarity of endogenous urinary and faecal nitrogen excretion by young men of different ethnic, socioeconomic and nutritional backgrounds, and the more efficient use of whole-egg N by young Nigerian men than by North American university students, have been reported (Nicol & Phillips, 1976~). Inter-individual variation of urinary and faecal N excretion was found to be significant, but intra-individual variation not significant, when Nigerian men were given a rice diet on two separate occasions. The physiological processes of adaptation to an efficient use of low-protein rice diets could be reversed within 2 or 3 weeks when they were given a diet containing amounts of high-quality protein greater than their customary intake (Nicol & Phillips, 1976b). Three of the important staple foods consumed in Nigeria are cassava (Manihot utilissima), rice and sorghum (Sorghum sativa) (Nicol, 1959a, b). The first objective of this paper was to reexamine findings, obtained some years …