Effects of Dietary Phytate, Calcium and Magnesium Levels on Zinc Bioavailability to Rats

Abstract

Young rats were fed diets containing 12 mg Zn/kg and varied levels of sodium phytate for 21-day ad libitum feeding periods. In experiment 1, Ca levels were 0.3, 0.5, 0.8 and 1.0%, and phytate:Zn molar ratio varied between 0 and 50. In experiment 2, Ca was maintained at 0.3%, Mg levels were 0.07, 0.22 and 0.37%, and phytate:Zn molar ratios were 0, 10, 20 and 30 at each Mg level. Major response criteria were body weight gain and tibia Zn accumulation. Weight gain was not influenced by Ca level in the absence of phytate or by phytate at 0.3% Ca; it was increasingly depressed as phytate was increased and by each increase in Ca in the presence of phytate. Total tibia Zn content was decreased at the highest Ca level in the absence of phytate; increasing the phytate progressively depressed tibia Zn at all Ca levels. Mg and phytate additions did not affect weight gain. Tibia Zn tended to be depressed by Mg and by phytate but these effects were significant only at the highest levels of the combined additions. These data corroborate and extend previously published findings on Ca and phytate effects on Zn utilization and show bone Zn accumulation to be a more sensitive criterion than weight gain in this connection. They also indicate that Mg exerts a less pronounced effect on Zn utilization in phytate-containing diets than does Ca.

Optimization of germination time and heat treatments for enhanced availability of minerals from leguminous sprouts

“…The heat treatments given to chickpea resulted in a greater reduction in PA:Zn when compared to PA:Zn ratio of mungbean and cowpea, the reason being longer cooking times in chickpea. Phytates found in legumes are thought to be major contributor to reduced availability of zinc (Forbes et al 1984). The PA:Zn molar ratios has been suggested to be an important determinant of zinc bioavailability from human diets (Oberleas and Harland 1981).…”

Nutritionally Enhanced Staple Food Crops

“…Several reports indicate phytic/zinc (P/Z) molar ratio a poor indicator of zinc bioavailability as it does not take into account the aggravating effects of calcium on zinc absorption in phytic acid containing diets (Forbes et al 1983(Forbes et al , 1984. However, phytate  calcium/zinc ratio in most of the soybean-based processed foods is a better predictor of zinc bioavailability than the phytate/zinc ratio (Fordyce et al 1987).…”

Effects of processing methods on the chemical composition of flour, <i>moinmoin</i> and <i>akara</i> from <i>mucuna</i> <i>pruriens</i>

“…Among the boiled and dehulled samples there were no significant differences. Removal of tannin and phytate by dehulling could have contributed to the observed decrease in minerals in the processed samples since many minerals are known to be bound to these compounds (Forbes et al, 1984) Boiling time and dehulling had a significant decrease in all the anti-nutrients evaluated. Boiling mucuna beans for 80min followed by dehulling (BDMF 80 ) led to a 25.8% decrease in L-dopa content.…”