Calcium, zinc and phytate interrelationships in some foods of major consumption in Nigeria

The calcium (Ca), zinc (Zn) and phytate (Phy) contents of 35 Nigerian foods were determined. Levels (mg/100 g) of Ca were 29–45 (legumes), 17–49 (cereals), 17–187 (spices) and 38–155 (tuber/roots) while the Zn levels were 0.55–2.00 (legumes), 0.67–1.84 (cereals), 0.34–4.92 (spices) and 1.35–7.07 (tubers/roots). Phytate levels were 14–344 (legumes), 112–287 (cereals), 35–184 (spices) and 0.0–1070 (tubers/roots). It was found that fermentation reduced Phy levels in Parkia filicoidea, Sorghum bicolor and Manihot esculenta while Phy level was increased in fermented Zea mays. The Phy:Zn molar ratios calculated for many legumes, cereals, tubers/roots and one spice analysed were greater than 20:1. Corresponding Ca:Phy molar ratios were generally low in legumes (except for Sphenostylis stenocarpa, 54:1), cereals and tubers/roots but generally high in spices (except Irvingia gabonensis, 2:1). Dioscorea rotundata, Dioscorea dumentorum and Manihot esculenta have respective molar ratios of Ca:Phy 1.8, 2.5 and 1.4 while the respective [ca] [Phy]/[Zn] molar ratios were 0.50, 0.54 and 0.62. These results suggest that the bioavailability of zinc in the Nigerian diet may be low due to the high phytate content of the staple foods.