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.
References
- ^Iron Fact Sheet for Health Professionals. MedlinePlus. National Institutes of Health (NIH) Office of Dietary Supplements (ODS). Updated 2023 Jun 15; cited 2023 December 5
- ^Lynch SR, Hurrell RF, Dassenko SA, Cook JDThe effect of dietary proteins on iron bioavailability in manAdv Exp Med Biol.(1989)
- ^Reddy MB, Hurrell RF, Cook JDMeat consumption in a varied diet marginally influences nonheme iron absorption in normal individualsJ Nutr.(2006 Mar)
- ^Bach Kristensen M, Hels O, Morberg C, Marving J, Bügel S, Tetens IPork meat increases iron absorption from a 5-day fully controlled diet when compared to a vegetarian diet with similar vitamin C and phytic acid contentBr J Nutr.(2005 Jul)
- ^Baech SB, Hansen M, Bukhave K, Jensen M, Sørensen SS, Kristensen L, Purslow PP, Skibsted LH, Sandström BNonheme-iron absorption from a phytate-rich meal is increased by the addition of small amounts of pork meatAm J Clin Nutr.(2003 Jan)
- ^Loganathan V, Bharathi A, Prince AM, Ramakrishnan JTreatment efficacy of vitamin C or ascorbate given as co-intervention with iron for anemia - A systematic review and meta-analysis of experimental studies.Clin Nutr ESPEN.(2023-Oct)
- ^Lane DJ, Richardson DRThe active role of vitamin C in mammalian iron metabolism: much more than just enhanced iron absorption!Free Radic Biol Med.(2014-Oct)
- ^Duarte AFM, Carneiro ACSV, Peixoto ATBMM, Montenegro DFP, Campos DSC, Alves APR, Costa ARMM, Fino APMOral Iron Supplementation in Pregnancy: Current Recommendations and Evidence-Based Medicine.Rev Bras Ginecol Obstet.(2021-Oct)