Mineral nutrient content of commonly consumed leafy vegetables in northern Ghana

Abstract

Leafy vegetables serve as the base of soups, a significant component of Ghanaian food recipes. The varying climatic conditions across Ghana and inefficient food distribution channels have resulted in the existence of different food crops in different regions. Anecdotally, Ghanaians generally believe that the consumption of Colocasia esculenta leaf improves iron status. In this study, the levels of mineral nutrients: calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na) and zinc (Zn) in the leaves of Hibiscus sabdariffa, Amaranthus spinosus, Hibiscus cannabinus, Solanum macrocapon and Vigna unguiculata that are popularly used in food recipes in northern Ghana (compose of the Northern, Upper East and Upper West Regions), were compared with the levels in Colocasia esculenta leaf. The leafy vegetables/greens consumed in northern Ghana were sourced from market centres in the Northern and Upper East Regions (savannah zone); Colocasia esculenta leaf was obtained from market centres in Ashanti Region (forest zone). The leaves were shredded and air-dried for 7 days. The dried leaves were ground and analysed for the mineral nutrients using Instrumental Neutron Activation Analysis. The Ca content of Hibiscus sabdariffa was significantly higher than that of Colocasia esculenta by 1.07-fold difference (p<0.05). However, compared with Amaranthus spinosus, Hibiscus cannabinus, Solanum macrocapon and Vigna unguiculata, the level of Ca in the Colocasia esculenta leaf was 1.23- to 1.84-fold significantly higher (p<0.05). The Fe level in the leafy vegetables commonly consumed in northern Ghana was significantly lower (2.92- to 70.60-fold difference, p<0.0001) compared with the Colocasia esculenta leaf. Significant differences (p<0.05) were also observed in the levels of K, Mg and Zn between the other greens studied and the Colocasia esculenta leaf. The differences were between 1.17- to 1.48-fold (K), 1.08- to 1.54-fold (Mg) and 1.15- to 2.59-fold (Zn). This study shows that the leafy vegetables commonly consumed in northern Ghana contain lower levels of the selected mineral nutrients analysed compared with those of Colocasia esculenta leaf. There is a need to find alternative greens that are available or could be cultivated in this part of the country.