Nitrogen balance study in young Nigerian adult males using four levels of protein intake

Abstract

1. The present study was carried out to estimate precisely, via the nitrogen balance technique, the protein requirement of Nigerians (earlier estimated via the obligatory N method) using graded levels of protein intake.2. Fifteen medical students of the University of Ibadan who volunteered to participate in the study were given graded levels of protein (0.3,0.45,0.6 and 075 g/kg body-weight per d) derived from foods similar to those usually consumed by the subjects.3. Each subject was given each of the dietary protein levels for a period of 10 d. Subjects were divided into two groups and the feeding pattern followed a criss-cross design with one group starting with the highest level of protein intake (0.75 g) and the second group starting with the lowest level of protein intake (03 g). Mean energy intake during each of the eleven experimental periods was maintained at 0 2 MJ/kg per d. After an initial 5 d adaptation period in each experimental period, 24 h urine and faecal samples were collected in marked containers for five consecutive days for N determination.4. Mean N balance during consumption of the four protein levels (030,045,06 and 075 g/kg) were -11.02 (SD 8.07), -990 (SD 6 9 , +9.70 (SD 4.15) and +513 (SD 4.62) respectively. Using regression analysis, the mean daily N requirement was estimated at 110.25 mg N/kg body-weight (0.69 g protein/kg body-weight). Estimates of allowances for individual variations to cover 97.5 % of the population adjusted this value to 0.75 g protein/kg body-weight. Net protein utilization for the diet at maintenance level was estimated at 57.5.The available internationally accepted information on protein requirements is based on premises not related to the physical biological and social factors unique to the Nigerian environment. The frequently cited minimum physiological nutrient requirement (the amount that is consistent with optimal health and above which no further improvement in health occurs) is at best a statistical approximation and usually derived from studies of privileged healthy Caucasians living under protected conditions.The often-quoted studies of Nicol & Phillips (1976) in Nigeria suggested that there may be adaptive changes in protein requirements in chronically undernourished Nigerians. These studies, conducted in the late 1950s, showed that Nigerian males were in positive nitrogen balance during short-term periods on a rice-protein intake of 0.44 g/kg body-weight per d. Ever since the study by Nicol & Phillips (1976) relatively few studies have been made in Nigeria in this interesting area of nutrient requirement, which for several reasons requires further examination. In a recent study by Atinmo et al. (1985), protein requirements of healthy Nigerian males were estimated, via the obligatory N loss method, to be 0.75 g/kg per d. Compared with the recommended value of 0.57 g/kg per d proposed by the Joint FAO/WHO ad hoc Expert Committee on Energy and Protein Requirements (World Health Organization, 1973) this level of requirement is quite high.The obligator...

Long-term evaluation of the adequacy of habitual diets to provide protein needs of adult Nigerian men

“…The composition of the diet, which was similar to the habitual diets of the subjects, is described by Atinmo et al (1988). The basic formula was the same for all subjects.…”

“…It provides no information on the occurrence and significance of either beneficial or deleterious adaptations that may arise from possible alterations in the pattern of N distribution and metabolism within the body (Yoshimura, 1972). From this point of view, therefore, the use of N balance studies of longer duration seem more desirable and acceptable, as information derived from them would include the effect of any forms of adaptations not noticed in short-term studies, such as those recently used to determine the protein requirements of adult and young adult Nigerians (Atinmo et al 1981(Atinmo et al , 1988). In the earlier study by Atinmo et al (1981), the protein requirement of the subjects was estimated at 0.60 g/kg bodyweight per d, while the safe level of protein intake was suggested to be 0.75 g/kg body weight per d.…”

“…This safe level of protein intake was also obtained from the extrapolation of the results of an N balance study in young Nigerians using graded levels of protein intake (Atinmo et al 1988). However, since this value in both cases was based on the results of short-term studies, further testing under free-living conditions and for a longer period was deemed necessary.…”

Chronic malnutrition: protein metabolism

“…The study reported by Atinmo et al (1988) from Nigeria is a good example of the results obtained with the adult protocol. The experimental diets were based on habitual foodstuffs, predominantly vegetable-based protein, and the four levels of protein intake were given in ascending order to half the group and in descending order to the other half.…”

An adaptive metabolic demand model for protein and amino acid requirements

“…The possibility of incomplete adaptation is a feature of the design of most N balance studies with diets randomised on the assumption that the order in which low-protein test diets are fed can influence the outcome. When diets are not randomised, different N balance curves are obtained according to the order in which intakes below habitual are fed (Atinmo et al 1988) implying that 2 weeks is not long enough. However, within the database analysed by Rand et al (2003), there were no discernable differences in outcomes according to the likely variation in habitual diets of the subjects (e.g.…”