Dietary Factors Modulate Iron Uptake in Caco-2 Cells from an Iron Ingot Used as a Home Fortificant to Prevent Iron Deficiency

Abstract

Iron deficiency is a major public health concern and nutritional approaches are required to reduce its prevalence. The aim of this study was to examine the iron bioavailability of a novel home fortificant, the "Lucky Iron Fish™" (LIF) (www.luckyironfish.com/shop, Guelph, Canada) and the impact of dietary factors and a food matrix on iron uptake from LIF in Caco-2 cells. LIF released a substantial quantity of iron (about 1.2 mM) at pH 2 but this iron was only slightly soluble at pH 7 and not taken up by cells. The addition of ascorbic acid (AA) maintained the solubility of iron released from LIF (LIF-iron) at pH 7 and facilitated iron uptake by the cells in a concentration-dependent manner. In vitro digestion of LIF-iron in the presence of peas increased iron uptake 10-fold. However, the addition of tannic acid to the digestion reduced the cellular iron uptake 7.5-fold. Additionally, LIF-iron induced an overproduction of reactive oxygen species (ROS), similar to ferrous sulfate, but this effect was counteracted by the addition of AA. Overall, our data illustrate the major influence of dietary factors on iron solubility and bioavailability from LIF, and demonstrate that the addition of AA enhances iron uptake and reduces ROS in the intestinal lumen.

Keywords: iron bioavailability; iron fortification; simulated gastrointestinal digestion.

Figure 1

Iron ingot (Lucky Iron Fish™ (LIF)) used to treat iron deficiency. The selected picture background shows the relative size of LIF compared to petit pois peas.

Figure 2

Concentration of total and soluble iron from the iron ingot (Lucky Iron Fish™ (LIF)) at (a) pH 2 and (b) pH 7 with or without AA. Data represent means ± SEM (n = 4). Means without a common letter differ (p < 0.05). n.d. means not statistically different.

Figure 3

Effect of iron ingot (Lucky Iron Fish™ (LIF)) on cellular viability. Caco-2 cells were treated with the iron released from LIF (LIF-iron) plus the final indicated concentration of ascorbic acid (AA) diluted in MEM (LIF-iron:MEM, 1:10, 1:3 and 1:1) for 24 h. Data represent means ± SEM (n = 8). Different letters indicate statistically significant differences (p < 0.05). n.d. means not statistically different.

Figure 4

Cellular ferritin response, as a surrogate of the iron uptake, from the iron ingot (Lucky Iron Fish™ (LIF)) with or without ascorbic acid (AA). Caco-2 cells were exposed for 24 h to the LIF-iron (0.1 mM Fe) with the indicated concentration of AA. Data represent means ± SEM (n = 6–8). Different letters indicate statistically significant differences (p < 0.05).

Figure 5

Iron uptake in Caco-2 cells exposed to simulated gastrointestinal digestates of peas and different dietary factors combined with the (Lucky Iron Fish™ (LIF))-iron. Cellular ferritin response exposed for 24 hour incubation with the in vitro gastrointestinal digestion containing LIF-iron plus ascorbic acid (0.5 mM) (a) with or without 1g of pea; and (b) with pea plus added tannic acid or phytic acid at the indicated concentrations. Data represent means ± SEM (n = 6–8). Means without a common letter differs (p < 0.05).

Figure 5

Iron uptake in Caco-2 cells exposed to simulated gastrointestinal digestates of peas and different dietary factors combined with the (Lucky Iron Fish™ (LIF))-iron. Cellular ferritin response exposed for 24 hour incubation with the in vitro gastrointestinal digestion containing LIF-iron plus ascorbic acid (0.5 mM) (a) with or without 1g of pea; and (b) with pea plus added tannic acid or phytic acid at the indicated concentrations. Data represent means ± SEM (n = 6–8). Means without a common letter differs (p < 0.05).

Figure 6

Effect of the iron ingot (Lucky Iron Fish™ (LIF)) on reactive oxygen species (ROS) generation. Cells were exposed to FeSO₄ (0.1 mM) or a similar LIF-iron concentration with or without AA. The intracellular ROS production was evaluated at 0, 30, 60 and 120 min. Data represent means ± SEM (n = 8). Different letters indicate statistically significant differences at each time point (p < 0.05).