Inositol Phosphate, Calcium, Magnesium, and Zinc Contents of Selected Breakfast Cereals

The concentrations in selected breakfast cereals of inositol tris-, tetra-, penta-, and hexakisphosphate (IP3, IP4, IP5, IP6) were determined by HPLC methodology. In addition, the calcium, magnesium, and zinc concentrations were determined by atomic absorption spectrometry. All cereals examined contained each of the inositol phosphate (IP) species. Wheat and oat cereals contained an overall average of 5 and 8 μmol/g, respectively, of IP6, representing 46 and 65% of total IP. The mean IP6 content of bran or bran added cereals was 13 μmol/g, 65% of the total IP content. Corn, rice, and most multigrain-based cereals contained lower concentrations of IPs. Whole grain or bran cereals to which no source of Ca or Zn was added averaged 10.9 μmol (0.44mg)/g of Ca, 0.48 μmol (0.032 mg)/g of Zn, and 57.1 μmol (1.4 mg)/g of Mg. Corn and rice cereals contained lower amounts of Ca, Zn, and Mg. Calculated indices of bioavailability, such as phytate/Zn and phytate/Ca molar ratios are most meaningful if based on values for IP6 or IP6 + IP5 rather than total IPs.