Iron, an essential mineral, plays a pivotal role in maintaining optimal health. Adequate iron levels in the body are essential for various physiological functions, including oxygen transportation, energy production, cognitive function, cell division, biotransformation and immune system support.
Iron is a required mineral for several processes within the body. Approximately 70% of the iron within the body is found in the hemoglobin of circulating red blood cells. Of the remaining iron distributed in other tissues, around 20% is in storage form as ferritin or hemosiderin in the liver, spleen and bone marrow. Myoglobin participates in muscle-specific oxygen exchange and accounts for the final 10%. Iron is a vital part of cytochrome enzymes for cellular respiration and metabolism, especially hepatic biotransformation. Trace amounts of iron are present in transferrin for iron blood transportation.
The human body has intricate mechanisms for iron absorption, transportation and utilization due to its inherently high redox potential. The primary site of iron absorption occurs in the duodenum, with the upper jejunum acting as a secondary iron absorption site especially during times of increased need. Dietary iron is present as animal source heme-iron or plant source non-heme iron. Heme iron is absorbed by the heme carrier protein 1 (HCP1). Dietary or supplemental non-heme iron is absorbed by the divalent metal transporter 1 (DMT-1) in the duodenum; however, absorption only occurs when iron is present in its reduced ferrous (Fe
2+) form. Supplemental iron can cause significant gastrointestinal (GI) irritation and side effects when the iron form has poor bioavailability due to the oxidation of iron to the ferric state (Fe
3+) in the stomach. Clinical research reports that up to 80% of people can experience GI side effects like abdominal cramping, nausea, constipation or diarrhea when taking low-bioavailability forms, resulting in a 50% early discontinuation rate.
Iron is essential for all people; however, certain populations may have an increased need for it. People with restricted diets who have reduced or no intake of the more bioavailable heme iron from animal sources can experience increased iron needs. Certain health conditions, especially GI conditions with malabsorption, can require additional intake to maintain optimal iron status. Lastly, those with an active lifestyle, especially endurance athletes, also have additional iron needs due to iron loss during perspiration, increased red blood cell lysis and muscle protein synthesis with exercise.
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