Effect of dietary protein levels on urea utilization in Papua New Guinea highlanders.

Abstract

Ability to utilize urea nitrogen for body protein synthesis was examined with Papua New Guinea (PNG) highlanders and Japanese (JPN). Eight male PNG highlanders and 8 male JPN were fed on a low protein diet containing 0.55 g protein/kg or an adequate protein diet containing l.34 g protein/kg for 1 or 2 weeks. The fate of 15N was measured after oral administration of 15N-labelled urea. There was no difference in 15N incorporation into serum protein between PNG highlanders and JPN receiving low protein diets. On the other hand, on the adequate protein diet, 15N incorporation in PNG highlanders was similar to that on the low protein diet, in contrast to that in JPN which was hardly detected in the adequate protein diet. When PNG highlanders take more protein than protein in their usual diet, they effectively incorporate ingested protein into their body protein and urea nitrogen is utilized for synthesis of body protein.

Dietary and nutrient intakes of 25 Ningerum (New Guinea) adult males at two times of the year

“…Koishi also argues that 0.33 g/kg represents the greatest level of adaptation to low protein intakes, further adaptation being impossible. New Guineans show the lowest levels of endogenous nitrogen excretion of any group measured in the world (Koishi, 1990), and various studies have been carried out to examine the mechanisms of this adaptation to low protein intake (Miyoshi et al, 1986;Oi et al, 1988;Rikimaru et al, 1985;Tanaka et al, 1980). The most promising possibility is that such populations are able to recycle urea nitrogen as amino-acids, to be used in protein synthesis.…”

A Noninvasive Method for Estimating Nitrogen Balance in Free-Ranging Primates

“…Indeed, dietary protein intake and urea concentrations correlate positively in humans and the former is commonly used as a diagnostic tool for studying protein deficiency in humans (Lechtig et al 1976(Lechtig et al , 1981Simmons 1972). A study on Papua New Guinea highlanders demonstrated that urea N is utilized in the synthesis of body protein in human subjects with low protein intake (Miyoshi et al 1986). Thus, it is likely that nonhuman primates utilize similar metabolic pathways to avoid tissue wasting.…”