Making dietary changes is an important step in providing iron that the body needs.
One of the best ways is to improve one’s dietary intake by consuming food that help increase iron intake (called “iron enhancers”) and by avoiding food that impair iron absorption also known as “iron inhibitors”.
Iron in the diet exists in two forms: heme and nonheme. Heme iron is mainly obtained from animal sources, while nonheme iron is mostly from plant sources. Compared to nonheme iron, heme iron is well absorbed by the body and is not generally affected by the dietary factors. Dietary factors such as animal tissue (meat, fish, and poultry, MFP) and ascorbic acid (AA) are known to enhance, whereas phytate, polyphenols, and calcium are known to decrease nonheme iron absorption. Although the nature of the factor in MFP is not clear, enhancing effect was shown in many human studies. The positive influence of animal tissue has been attributed to unknown “factors” possibly proteins or other constituents that can prevent iron from polymerizing and maintain iron in a stable soluble form. AA is shown to overcome the inhibition even in the presence of phytate and polyphenols. Because of the reducing capability of ascorbic acid, it forms soluble chelates with iron, thereby preventing the formation of insoluble and unabsorbable iron compounds that may be formed with phytates and polyphenols. Phytate has been shown to inhibit nonheme iron absorption in a dose-dependent manner, but its content can be easily reduced by many simple food processing methods. The degree of inhibition by polyphenols depends on the type (food sources) and the amount of polyphenols in the diet. Although it is not that clear, the inhibition of iron absorption by calcium depends on the source of calcium (supplement vs dietary calcium) and the composition of the meal. The effect of all of the dietary factors is clear from single meal human studies, but magnitude of effect was diminished in the context of mixed diets that contained various enhancers and inhibitors. However, it is difficult to conduct those kinds of studies in humans.