Iron

Characteristics: Iron is a mineral that occurs naturally in many foods, is added to some food products, and is available as a dietary supplement. Iron is an essential component of hemoglobin, the red blood cell protein that carries oxygen from the lungs to the tissues. Iron as a component of myoglobin, another protein that provides oxygen, supports muscle metabolism and healthy connective tissues. Iron is also essential for physical growth, neurological development, cell function and the synthesis of certain hormones. Dietary iron comes in two main forms: heme and non-heme. Iron-fortified plants and foods contain only non-heme iron, while meat and seafood contain both heme and non-heme iron.

Absorption: Most of the 3 to 4 grams of elemental iron in adults is in hemoglobin. Much of the remaining iron is stored as ferritin or hemosiderin in the liver, spleen, and bone marrow, or is found in myoglobin in muscle tissue. Transferrin is the main protein in the blood that binds to iron and transports it throughout the body. People usually lose only small amounts of iron in the urine, stool, gastrointestinal tract, and skin. Losses are greater in menstruating women due to blood loss. Heme iron has a higher bioavailability than non-heme iron. The bioavailability of iron is approximately 14‒18% from a mixed diet that contains significant amounts of meat, seafood, and vitamin C (ascorbic acid, which increases the bioavailability of non-heme iron) and 5‒12% from a vegetarian diet. There are many iron absorption inhibitors. Polyphenols, or tannins, can inhibit intestinal absorption of non-heme iron; however, they do not have chelating effects on boiled heme iron. E.g. drinking tea reduces the absorption of non-heme iron by 60% and drinking coffee by 40%. Adding milk to tea can reduce the chelating effects. Phytates (whole grains, legumes, corn), oxalic acid (spinach, chard, chocolate, berries, tea) and phosvitin (a protein found in egg yolks) significantly affect iron absorption in a negative sense. Calcium consumed in a dose of 300‒600 mg can reduce the bioavailability of both non-heme and heme iron. Zinc competes with iron for absorption and therefore can reduce iron absorbability by 66-80%. Manganese can reduce absorption by 22-40%.

Dietary supplements: Iron is available in many dietary supplements. Multivitamin/multimineral supplements with iron, especially those designed for women, usually provide 18 mg of iron. Supplements for men or seniors often contain less or no iron. Single-ingredient supplements provide up to 65 mg of iron. Commonly used forms of iron in supplements include ferrous and ferrous salts such as ferrous sulfate, ferrous gluconate, ferrous citrate, and ferrous sulfate. Due to its higher solubility, divalent iron in dietary supplements is more biologically available than trivalent iron. High doses of iron (45 mg/day or more) can cause gastrointestinal side effects such as nausea and constipation. Other forms, such as heme iron polypeptides, carbonyl iron, chelates with amino acids, and complexes with polysaccharides, may have fewer gastrointestinal side effects than ferrous or ferrous salts. Pay attention to the fact that different forms of iron in supplements contain different amounts of elemental iron. For example, ferrous fumarate contains 33% elemental iron by weight, while ferrous sulfate 20% and ferrous gluconate 12%.
Natural sources: Among the richest dietary sources of heme iron are lean meats and seafood. Sources of non-heme iron include nuts, beans, vegetables and fortified cereals. Breast milk contains highly bioavailable iron, but in amounts that are insufficient to meet the needs of infants older than 4 to 6 months. Some plant foods that are good sources of iron, such as spinach, have low iron bioavailability because they contain iron absorption inhibitors.

Effect: Iron is an essential mineral that facilitates the transport of oxygen, its storage in the body and is part of many enzyme systems.

Deficiency: Iron deficiency is especially common in young children, women of reproductive age and pregnant women. It is often associated with poor diet, malabsorption disorders and blood loss. In developing countries, iron deficiency is often the result of enteropathies and blood loss associated with gastrointestinal parasites. Iron deficiency is the most common cause of anemia. Iron deficiency generally presents with gastrointestinal disorders, weakness, fatigue, difficulty concentrating, and impaired cognitive (brain) and immune function, physical or work performance, and body temperature regulation. In infants and children, deficiency can lead to psychomotor and cognitive abnormalities that can lead to learning disabilities without treatment. Some evidence suggests that the consequences of early-life deprivation persist into adulthood. The most at-risk groups are pregnant women, infants and small children, menstruating women, blood donors, people with cancer, diseases of the digestive tract and chronic heart failure.

Recommended daily dose: adult: 8 mg for men, 18 mg for women (27 mg during pregnancy, 9 mg when breastfeeding), 51+: 8 mg for men, 8 mg for women.

Side Effects: Oral supplements may cause gastrointestinal disturbances such as nausea, diarrhea, constipation, heartburn, or blackened stools. While taking supplements with food reduces these side effects. Liquid preparations can change the color of teeth - brush your teeth after use. Intermittent dosing on a weekly basis rather than a daily basis may help.

Interactions: Calcium may interfere with iron absorption. For this reason, some experts recommend that people take individual calcium and iron supplements at different times of the day. Supplements containing 25 mg of iron or more may reduce absorption and plasma concentrations of zinc. Iron reduces the absorption of levodopa used to treat Parkinson's disease and restless legs syndrome. Levothyroxine is used to treat hypothyroidism, goiter, and thyroid cancer. Concomitant administration of iron and levothyroxine may lead to a clinically significant reduction in the efficacy of levothyroxine in some patients, therefore a 4-hour interval is recommended. Stomach acid plays an important role in the absorption of non-heme iron from the diet. Because proton pump inhibitors such as lansoprazole and omeprazole reduce the acidity of stomach contents, they may reduce iron absorption. Iron reduces the absorption of quinolone antibiotics. Take them 2 hours before or 4-6 hours after your iron dose. Iron binds with sulfasalazine, therefore its effect is reduced. Vitamin C increases the absorption of iron.

Pregnancy: safe in usual doses.

Breastfeeding: safe in usual doses.

Toxicity: Adults with normal bowel function are at very low risk of overdosing on iron from food sources. Case reports, some of which involved doses of 130 mg of iron, suggest that some people develop more severe gastrointestinal symptoms. The most prominent symptoms are hemorrhagic necrosis of the gastrointestinal tract, which is manifested by vomiting, bloody diarrhea, and hepatotoxicity (liver damage). Iron intoxication causes severe organ damage and eventually death. Acute iron overdose or accumulation may progress to shock and/or impaired consciousness. Iron overdose in pregnant women has been associated with spontaneous abortion, premature birth, and maternal death. Excessive iron accumulation is being investigated as a potential contributing factor to the development of diseases such as Parkinson's and Alzheimer's.

Caution: Iron supplements should not be used in hemochromatosis, hemosiderosis, thalassemia, and sideroblastic anemia.