Potential of food-to-food fortification with cowpea leaves and orange-fleshed sweet potato, in combination with conventional fortification, to improve the cellular uptake of iron and zinc from ready-to-eat maize porridges

An emerging tool in the fight against the high prevalence of micronutrient deficiencies in sub-Saharan Africa is the production of nutritionally enhanced staple food products, through food-to-food fortification with micronutrient-dense fruits and vegetables. This study investigated food-to-food fortification with cowpea leaves (CL) and orange-fleshed sweet potato (OFSP) in combination with conventional micronutrient fortification and fermentation on the mineral and antinutrient contents and Caco-2 cellular uptake of iron and zinc from ready-to-eat maize porridges. The amount of iron and zinc taken up from maize porridges (0.05 and 0.06 mg/100 g, db, respectively) was increased more after fortification with CL, compared to OFSP (0.32 and 0.23 mg/100 g, db versus. 0.11 and 0.04 mg/100 g, db, respectively). Despite the moderate cellular uptakes of iron and zinc from the CL fortified porridges (2.71% and 3.10%, respectively) compared to the OFSP fortified porridges (6.51% and 5.22%, respectively), the CL fortified porridges had much higher high iron and zinc contents (12.2–14.1 and 7.6–8.9 mg/100 g, db versus. 2.1–3.7 and 1.5–2.7 mg/100 g, db, respectively). This highlights the importance of increasing both the mineral content and bioavailability when fortifying a product. Even when a food product contains substantial antinutrients such as CL, if the mineral content and contents of bioavailability enhancers are high enough, the amounts of bioavailable iron and zinc can still be improved