Bioavailability of iron and zinc from Digera muricata (Kondhra) supplemented diets: Implications for combating micronutrient deficiency in adolescent populations

Abstract:

Micronutrient deficiency, particularly iron and zinc deficiency, constitutes a major public health challenge for adolescent populations in South Asia and the Middle East, where dietary diversification through food fortification offers a cost-effective intervention pathway. This research evaluated the in vitro bioavailability of iron and zinc from diets supplemented with Digera muricata (Kondhra) leaf powder at 5%, 10%, and 15% dry matter incorporation levels, using a simulated gastrointestinal digestion protocol (pepsin-pancreatin sequential hydrolysis) followed by Caco-2 human intestinal cell uptake assays conducted at Isfahan Institute of Technology, Iran, during 2022–23. The influence of anti-nutritional factors — phytic acid, oxalic acid, and condensed tannins — on mineral bioaccessibility was systematically quantified across incorporation levels. Maximum iron dialyzability (24.6%) was observed at the 10% incorporation level, declining marginally at 15% (22.8%), suggesting that anti-nutritional factor accumulation at higher incorporation levels attenuates the additional mineral load. Caco-2 cell uptake assays confirmed this trend, with the 10% DM formulation yielding 2.84±0.18 nmol iron/mg protein, representing a 3.56-fold increase over the unsupplemented control. Concurrent addition of ascorbic acid (50 mg) to the 10% DM formulation enhanced Caco-2 iron uptake by 92.9% relative to the unsupplemented formulation, identifying ascorbic acid co-consumption as the most effective strategy for maximising bioavailable iron delivery from D. muricata-supplemented diets. The phytate-to-iron molar ratio declined from 3.82 in control to 2.82 at 15% DM incorporation, remaining below the WHO threshold of 6.0 for adequate iron bioavailability across all tested levels, and well below the more stringent threshold of 1.0 recommended for high-bioavailability diets. These findings establish 10% DM incorporation of D. muricata leaf powder as the optimal level for iron bioavailability in supplemented food products targeting adolescent micronutrient deficiency.