Urinary calcium and calcium balance in young women affected by high protein diet of soy protein isolate and adding sulfur-containing amino acids and/or potassium.

Abstract

SummaryThe effects of sulfur-containing amino acids (SAA) and potassium (K) on urinary excretion and retention of calcium (Ca) of 27 young Japanese women were studied. A basal diet low in protein level (50g per day) was fortified by meat or soy protein isolate (SPI) to a protein level of 100g per day, and effects of addition of apple to these high protein diets, and addition of SAA and/or potassium (K) to the high SPI diet, especially on urinary Ca excretion, were studied. The addition of meat which increased protein intake to 100g caused the increase in apparent absorption and urinary excretion of Ca with increased excretion of urinary sulfur (S), phosphate, ammonia, and titratable acids (TA), whereas addition of SPI did not. The addition of apple to high meat diet decreased absorption and urinary excretion of Ca. Urinary Ca, S, K, ammonia, and TA excretion increased by the addition of SAA to high SPI diet in a manner similar to the meat diet. Consequently, SAA-supplemented diet had a significantly negative effect on Ca retention. In SPI+SAA, K diet period, urinary K excretion markedly increased, and increments in urinary Ca, ammonia, and TA excretion were reversed. These changes observed in SPI+SAA, K diet period were similar to those by adding apple to meat diet without any effect on Ca absorption. The results suggest that the hypercalciuria induced by high meat diet is mainly caused by high content of SAA and may be reversed by the ingestion of K-rich foodstuffs, and soy protein does not induce hypercalciuria because of it contains less SAA than animal protein.

High-protein Weight-loss Diets: Are They Safe and Do They Work? a Review of the Experimental and Epidemiologic Data

“…59,62,[71][72][73][74][75][76][77] The importance of sulfur-containing amino acids as the causative mechanism for urinary calcium loss is highlighted by direct comparisons with ingestion of soy protein that has relatively few sulfur-containing amino acids and does not induce hypercalciuria. 78 However, the total protein content of the diet was found to correlate strongly with sulfuric acid production, and correlations with animal protein content are only marginally stronger. 60 By contrast with the relatively consistent data from short-term studies suggesting negative effects of highanimal protein intake on bone, long-term data from epidemiologic studies are con icting.…”

The Role of Soy in Vegetarian Diets

“…And in fact, several older studies found this to be the case [130,131]. However, in recent years the adverse effects of SAA on bone haven’t been demonstrated in clinical studies evaluating calcium balance [132,133] or in epidemiologic studies evaluating BMD [124] and fracture risk [134].…”

Excess Casein in the Diet Is Not the Unique Cause of Low-Grade Metabolic Acidosis: Role of a Deficit in Potassium Citrate in a Rat Model

“…In addition, phosphate excretion was also higher in rats on the high-protein diets, probably as a consequence of casein P-serine and P-threonine catabolism. Moreover, it is known that the higher phosphate excretion during acidosis is due to impaired renal tubular phosphate reabsorption and proximal tubular apical brush border membrane Na/PO 4 cotransport activity [12,13] . Glutamine metabolism by kidneys is a major process to counteract acidosis through bicarbonate and ammonium production (hence H + trapping) and urine measurements have actually shown that ammonium excretion was higher with the 26% protein diet.…”