Heme iron is more readily absorbed compared to non-heme iron, but the bioavailability of iron in the body can be influenced by several foods and dietary components. In individuals following a mixed diet, which includes fruit, vegetables, meat, and seafood, the bioavailability of iron ranges from approximately 14% to 18%. For vegetarian diets, iron bioavailability can range from 5% to 12%.[1]
Animal protein appears to increase non-heme iron absorption from non-meat produce (e.g., vegetables, grains) when these foods are consumed in the same meal. However, this effect was less pronounced for wheat than for other plant-based foods.[2][3] Additionally, studies have yielded mixed results regarding the combination of pork meat with meals high in phytates (which can be found in certain legumes and vegetables), indicating that phytate may counteract the positive effects of animal protein on non-heme iron absorption.[4][5]
It’s often recommended that iron be taken with Vitamin C (ascorbic acid) supplements or vitamin C-rich foods. Theoretically, ascorbic acid can facilitate the reduction of ferric iron to its more bioavailable form (ferrous iron), and can chelate iron ions (i.e., bond with them) to enhance their solubility and absorption from the intestines into the bloodstream.[6] Furthermore, ascorbate (a mineral salt of ascorbic acid) regulates the uptake of iron by transferrin, which is why scurvy (a disease resulting from a vitamin C deficiency) is often associated with some degree of iron-deficiency anemia.[7] However, two meta-analyses both found no difference in hemoglobin and ferritin levels when iron was supplemented with vitamin C, compared to iron alone,[6][8] suggesting that there is still limited clinical data on the benefits of combining iron and vitamin C.