Dark green leafy vegetables (DGLV) are considered important sources of iron and vitamin A. However, iron concentration may not indicate bioavailability. The objectives of this study were to compare the nutrient content and iron bioavailability of five sweetpotato cultivars including three orange-fleshed types with other commonly consumed DGLV: cocoyam, corchorus, baobab, kenaf and moringa in Ghana using the in vitro digestion/Caco-2 cell model. Moringa had the highest amounts of iron absorption enhancers on an as-would-be-eaten basis, β-carotene (14169 µg/100 g, p <0.05) and ascorbic acid (46.30 mg/100 g, p <0.001), and the best iron bioavailability (10.28 ng ferritin/mg protein). Baobab and an orange-fleshed sweetpotato with purplish young leaves had lower iron bioavailability (6.51 and 6.76 ng ferritin/mg protein, respectively) compared with that of moringa although these three greens contained similar (p > 0.05) iron (averaging 4.18 mg/100 g) and β-carotene levels. The ascorbic acid concentration of 25.50 mg/100 g in the cooked Baobab did not enhance iron bioavailability. Baobab and the orange-fleshed sweetpotato with purplish young leaves contained the highest level of total polyphenols (1646.75 and 506.95 mg Gallic Acid Equivalents/100 g, p <0.001, respectively). This suggests iron bioavailability in greens could not be inferred based on the mineral concentration. Based on the similarity of the iron bioavailability of the sweetpotato leaves and cocoyam leaf (widely-promoted “nutritious” DGLV in Ghana), the former greens have an added advantage of increasing dietary intake of provitamin A.

Keywords: β-carotene; Caco-2 cell; iron bioavailability; leafy vegetable; polyphenols