Effects of Phytate Removal from Soybean Protein on Calcium, Magnesium and Zinc Absorption of Rats

Abstract

Effects of phytate removal from soybean protein on mineral (Ca, Mg and Zn) absorption were examined. Growing male Wistar rats were fed a 20% protein diet containing phytate-free soybean protein (PFS), soybean protein isolate (SPI) or casein for 10 days. The total phosphorus (P) content of the diet was adjusted to 0.59% by adding inorganic phosphate (P₁). Almost all of the P in the PFS diet was exogenously added P₁, and therefore further adjustment of the dietary P₁ level was also done by adding 0.59% P₁ to the SPI and casein diets (designated SPI-I and Casein-I respectively). The results obtained were as follows: 1) Ca absorption in rats fed the PFS diet was only 1% higher than that in rats fed the SPI and SPI-1 diets. 2) On the other hand, Mg and Zn absorption in rats fed the PFS diet was 5-10% higher than that in rats fed the SPI and SPI-I diets. 3) Mineral (Ca, Mg and Zn) absorption in rats fed the SPI and SPI-1 diets was the same as that in rats fed the casein and Casein-I diets. These results suggest that phytate removal from soybean protein improves the absorption of Mg and Zn in rats fed SPI or casein.