The zinc, calcium, copper, manganese, nonstarch polysaccharide and phytate content of seventy-eight locally grown and prepared African foods

Suboptimal mineral nutrition may be prevalent in Africa; however, research is limited by the absence of reliable data on the mineral, dietary fiber and phytate content of local foods. For this reason, 75 Ghanaian foods and 3 Malawian cereal flours were analyzed for Zn, Ca, Cu, and Mn by atomic absorption spectrophotometry, nonstarch polysaccharide (NSP) was analyzed by the Englyst method, and phytic acid was analyzed using ion-exchange procedures; some foods were analyzed using the HPLC method. On a fresh weight basis (mg/100 g FW), legumes and animal products had the highest mineral content ranging from 1.2 to 8.5 (Zn), 49 to 4638 (Ca), 0.15 to 1.49 (Cu) and 0.06 to 2.67 (Mn), for animal products; and from 0.4 to 6.0 (Zn), 10 to 442 (Ca), 0.08 to 1.47 (Cu), and 0.28 to 14.12 (Mn) for legumes. In contrast, cereals had the lowest Ca and Cu content, ranging from 1.3 to 16 and from 0.01 to 0.19 (mg/100 g FW), respectively; roots, tubers, plantain, and vegetables had the lowest Zn content (0.1-0.9 mg/100 g FW). The NSP content of groundnuts and bean cakes (mg/100 g FW), and the phytate content of cereals and legumes (g/100 g FW) were higher than those of other plant foods (for NSP, 5.8-6.3 vs 0.2-4.6 for other plant foods; and for phytate, 66-279 for cereals; and 118-339 for legumes vs 0-118 for other plant foods). For cereal flours, over 90% of the inositol phosphates were inositol hexa- and pentaphosphates, compared to less than 65% in the fermented cereal products. The molar ratios of phytate:Zn (P:Z) of the cereal staples and most of the starchy staples were similar despite the higher phytate content of the former (8:34; for cereals vs 4:24 for cassava products and yams). Hence, decreasing the proportion of cereals to starchy staples would probably not improve the bioavailability of Zn. However, the addition of groundnuts, fermented locust bean seeds (dawadawa), or fermented kapok seeds (kangtong) to soups and stews, and the use of small fish would increase the mineral content of these dishes.