The Effect of Calcium, Ascorbic Acid and Tannic Acid on Iron Availability from Arthrospira Platensis by Caco-2 Cell Model

There are several dietary factors that are known to affect the bioavailability of iron such as protein, calcium, ascorbic acid, polyphenol and phytate. The aim of this study was to determine iron bioavailability from spirulina (Arthrospira platensis) in the presence of calcium, ascorbic acid (AA) and tannic acid (TA). The experiments were conducted using in vitro digestion/Caco-2 cell culture system. Comparison was made with ferrous sulphate (FeSO4) as a reference. At low calcium concentrations (1:05, 1:10, 1:15, 1:20 Fe:Ca molar ratios), iron bioavailability from spirulina was significantly better than from FeSO4. However, at higher calcium concentrations (1:37, 1:75, 1:149 Fe:Ca molar ratios), iron bioavailability from spirulina was found to be similar to that from FeSO4. Addition of ascorbic acid of different concentrations (1:0.5, 1:1, 1:1.5 and 1:2 Fe:AA molar ratios) increased iron availability from FeSO4 more than from spirulina. The concentrations of tannic acid (1:1, 1:1.4 and 1:2 Fe:TA molar ratios) used in this study reduced iron availability from spirulina but not from FeSO4. Iron from spirulina by itself is highly bioavailable but consumers should be aware of factors that could inhibit its bioavailability. tion/Caco-2 cell culture method. The potential of using Caco-2 cells as a model for studying iron bioavailability has been highlighted in various studies (Glahn et al., 1998; Serfass & Reddy, 2003). Caco-2, when grown on microporous membranes in bicameral chambers, differentiates spontaneously into bipolar enterocyte that exhibit many of the characteristics of normal epithelial cells. These include microvilli of the brush border membrane, tight intercellular junctions, the excretion of brush border associated enzymes and dome formation (Vachon & Beaulieu, 1992). The design of the bicameral chambers permits study of iron uptake from the apical chamber, transport into the cell and vectorial secretion of iron into the basal chamber. MATERIALS AND METHODS All the enzymes and chemicals were obtained from Sigma Chemical (St. Louis, MO, USA) unless noted otherwise. Deionized water was used throughout the study unless noted otherwise.