In-vitro dialysability of iron in green leafy vegetables and seasonal variation of total iron content

Abstract

Green leafy vegetables are considered a good source of iron in Sri Lankan diets, particularly among populations dependant on plant based diets. The iron status of diets can be improved by including iron rich plant sources and enhancing the bioavailability by cooking/processing. The mean total iron content ± SD of the green leafy vegetables studied were as follows (expressed as fresh weight, mg/100g): sarana (Trianthema portulacastrum L.): 6.7±1.5, rathu thampala (Amaranthus lividis.L.): 13.4±2.7; nivithi (Basella alba L.): 1.3±0.6; kathrumurunga {Sesbania grandiflora (L.) Poir.}: 3.2±0.7; mukunuwenna {Alternanthera sessili (L.)Dc.}: 1.8+0.3; kankun (Ipomoea aquatica. Forssk.): 1.9±0.9 and gotukola {Centella asiatica (L). Urban): 5.2±1.6. The seasonal variation observed was not significant p>0.05 over the period of one year. These values indicate that the contribution of iron from green leafy vegetables to the diets is low. The freshly cooked and dehydrated - cooked samples (hot-air drier at 55°C) were blended with water and subjected to simulated gastro-intestinal digestion procedures, following which the proportion of iron that diffused through a semi permeable membrane (molecular mass cut-off 10 kDa) determined-cooked as the dialyzable iron. This was quantified spectrophometrically at 535 mn. The dialysable iron extracted from the freshly cooked and dehydrated - cooked green leafy vegetables ranged between 1.5-13.4 % and 3.6-17.6% respectively. Accordingly the best sources of available iron from green leafy vegetables are sarana, kathrumurunga and rathu thampala.