Table 4.

Human studies with soy protein on renal calcium metabolism

Ref.	Study design	Kidney function	Subjects/group	Amount of soy protein used	Control/comparator protein	Duration of intervention	Outcomes	Notes
Breslau et al[119]	RC	Normal	15 subjects completed animal and ovo-vegetarian diet phases; 10 completed all 3 phases (including vegetarian)	Soy protein accounted for most of the 75 g protein/d in vegetarian phase; accounted for an unspecified but lower amount in ovo-vegetarian phase	Animal protein accounted for most of the 75 g per day in the animal protein phase; consisted of dairy, beef, chicken and fish	12 d No WO	Serum uric acid concentrations were significantly lower with the vegetarian and ovo-vegetarian diets compared to the animal protein diet (P < 0.01); urinary uric acid excretion was significantly lower in ovo-vegetarian diet vs animal diet only (P < 0.02)	Diets were constant for Ca, P, Na and total protein
							Urinary Ca and P were significantly lower in vegetarian diet compared to beef diet (P < 0.02); urinary oxalate was significantly higher in vegetarian vs beef diet (P < 0.02)
							Animal protein diet resulted in lower PTH level vs vegetarian diet (P < 0.05)
							Serum 1,25-(OH)2D was higher in the vegetarian vs animal protein diet(P < 0.01)
Roughead et al[120]	RC	Normal PM women	13 female subjects	25 g soy protein substituted for 25 g meat protein	25 g meat protein in control diet	7 wk	Ca retention was not affected by substituting soy protein for meat protein
							Urinary pH was higher on the soy diet compared to the control diet (P < 0.0001); renal acid excretion was lower during soy diet (P = 0.0001) however urinary Ca excretion was similar between soy and meat diets
							Substitution of soy protein for meat protein did not affect bone metabolism as indicated by no differences between diets in a number of specific bone biomarkers
							No differences between soy and meat protein diets in plasma lipid or hemostatic measures

Ca: Calcium; Na: Sodium; P: Phosphorus; PM: Postmenopausal; PTH: Parathyroid hormone; RC: Randomized crossover trial; WO: Washout.