E A Oddoye | PubMed Health

PubMed1979

Protein-induced hypercalciuria: a longer term study.

Urine calcium excretion is known to be directly correlated with the level of dietary protein intake. In this experiment we examined the persistence of the hypercalciuria induced by the consumption of high protein diets, and the mechanism of the calciuric response. In a 95-day metabolic study, each of six adult male subjects received formula diets supplying 12 g nitrogen or 36 g nitrogen, and approximately 1400 mg calcium per day. Urine calcium increased rapidly and significantly from an average of 191 mg/day on the 12 g nitrogen diet to 277 mg/day on the 36 g nitrogen diet. There was no significant difference in the apparent absorption of calcium, so that overall calcium balance was -37 mg/day on the 12 g nitrogen diet, and significantly lower at -137 mg/day in subjects consuming the high protein diet. Levels of urinary hydroxyproline, serum insulin, and parathyroid hormone were not significantly increased by high intakes of protein. A decrease in the fractional reabsorption of calcium by the kidney seems to be the most likely cause of the protein-induced hypercalciuria. The consumption of high calcium diets is unlikely to prevent the negative calcium balance and probable bone loss induced by the consumption of high protein diets.

Adult↗

PubMed1979

Nitrogen balance studies in humans: long-term effect of high nitrogen intake on nitrogen accretion.

Six healthy young adult male participants were confined to a metabolic ward for 105 days. Two nutritionally adequate purified diets providing 12 and 36 g of nitrogen per day were randomized in two metabolic periods of approximately 50 days each. The objective of this study was to verify whether or not positive nitrogen balance is a concomitant of increased nitrogen intake under the most rigorously controlled conditions, and if so, whether adaptation could occur if the experiment was conducted for sufficiently long periods of time. The mean nitrogen balance was slightly negative for most participants when fed the 12 g N diet. However, individual variability was so large that statistically all the participants can be considered in balance. In view of this, we agree with other investigators who have suggested that balance should be considered as an area which takes into account variabilities such as intake, output and biological factors. On the 36 g N diet, all the participants exhibited strong positive balances, about 1.6 g/day, which were not as high as reported by other investigators but which persisted for as long as they were fed this diet. This positive balance could not seem to be explained on the basis of methodological errors or to any unmeasured nitrogen losses. There was no significant trend towards adaptation as claimed.

Adaptation, Physiological↗