Iron

Iron is a mineral that is found in every human cell and is vital to the health of the human body. The human body contains approximately 4 grams of iron that is primarily found in cells, linked with protein to form hemoglobin, the oxygen-carry molecule.

The two forms of dietary iron are heme iron and non-heme iron. Heme iron is located only in animal flesh, derived from hemoglobin as well as myoglobin, which is in animal tissues. Plant foods and dairy foods contain non-heme iron.

Physiological functions of iron

• Enhances oxygen distribution throughout the body
• Keeps the immune system healthy
• Assists in energy production

 

Physiological events that may signal a need for greater iron intake

• Fatigue and weakness
• Decreased ability to concentrate
• Dizziness
• Headaches
• Depression
• Apathy
• Increased susceptibility to infections
• Hair loss
• Brittle nails

 

Functions of iron

Distribution of oxygen

Iron is a vital component of hemoglobin, the oxygen-carrying molecule found in red blood cells. The ability of red blood cells to pick up oxygen from the lungs and distribute it to tissues throughout the body is attributed to the presence of iron in the hemoglobin molecule. When there is a deficiency of iron, less hemoglobin is produced and subsequently less oxygen is deliver to the tissues.

Myoglobin is another protein in which iron is an important component. Like hemoglobin, myoglobin also carries oxygen, delivering it to muscle cells, especially those of the skeletal and heart muscles.

Production of energy

Several enzymes involved in energy production, such as iron catalase, iron peroxidase and the cytochrome enzymes, feature iron as a central constituent. Iron also plays a role in the production of carnitine, a nonessential amino acid that is integral to the conversion of fat to usable energy. Sufficient iron is also necessary to maintain immune system function.

Causes and symptoms of iron deficiency

Iron deficiency is one of the most common nutrient deficiencies in the United States and around the world. Poor iron status may be caused by a variety of factors including inadequate dietary intake, parasitic infection, and/or medical conditions that cause internal bleeding. It may also be a result of reduced iron absorption that can be caused by low stomach acid, common in the elderly and in people who frequently use antacids. Additionally, drinking coffee, tea and carbonated soft drinks can lead to compromised iron status since the caffeine, tannic acids and phosphates found in these beverages inhibit iron absorption. Iron absorption may also be reduced in the presence of phytates, found in whole grains, and oxalates, found in spinach and chocolate, since these compounds form complexes with iron that cannot be absorbed through the digestive tract.

People who donate blood regularly, individuals who use medications that interfere with iron absorption and women with excessive menstrual bleeding may also be at risk for iron deficiency. Increased physiological need for iron, which occurs in children during rapid growth periods and women during lactation and pregnancy, also increases iron absorption. Vegetarians, children and the elderly often have inadequate dietary intake of iron.

Microcytic and hypochromic anemia is caused by iron deficiency. This condition is characterized by undeveloped red blood cells that lack hemoglobin and therefore have diminished oxygen carrying capacity. Yet, even before iron deficiency anemia develops, those who have reduced iron stores can experience a host of symptoms. These include fatigue, weakness, loss of stamina, increased susceptibility to infections, decreased ability to concentrate, dizziness, headaches, depression, apathy, hair loss and brittle nails. In children, learning disabilities and a lower IQ are associated with iron deficiency. Poor iron intake can also lead to the development of an unusual eating behavior known as pica, in which individuals eat unsuitable and/or inedible materials such as dirt, clay, charcoal, laundry starch and/or lead paint chips.

Causes and symptoms of iron toxicity

The acute ingestion of large quantities of iron-containing supplements can cause iron poisoning that can manifest in nausea, vomiting, gastrointestinal lining damage, shock and liver failure. Iron poisoning is one of the leading causes of death among children.

Symptoms of chronic iron overload, or excess iron storage, include nausea, dizziness, appetite loss, weight loss, fatigue, headaches, shortness of breath and development of a bronze or gray hue to the skin. Chronic iron overload is believed to only occur in people who take iron supplements, receive regular blood transfusions or those who have the genetic iron storage disorder known as hemachromatosis, a condition where iron is deposited in tissues throughout the body and can manifest in the development of cirrhosis, diabetes or cardiac insufficiency.

Iron overload is not likely to develop from dietary sources alone. Yet, since men do not regularly experience iron losses as women do during menses, they may be at a greater risk for problems related to excess iron. In recent years, research findings have suggested that excess iron intake and storage may be associated with development of heart disease and cancer, especially in men. Individuals with rheumatoid arthritis have also been found to have increased levels of iron residing in their joints.

In 2001 the Institute of Medicine at the National Academy of Sciences set the Tolerable Upper Intake Level (UL) of 40 milligrams per day for infants and children through the age of 13. Forty-five milligrams per day is the UL for individuals age 14 and older. This UL applies to general use of iron and does not apply to persons who receive iron while under medical supervision.

Effects of cooking, storage and processing on iron

The milling process that whole grains undergo during refinement removes the bran and the germ, the locations of most of the grains iron stores. Consequently, approximately three-quarters of the grains natural iron content is lost during processing. While refined grains are fortified with iron, this form of iron is less absorbable than that which occurs naturally in the grain. While cooking with iron cookware will increase the iron content of food, it is a practice that can potentially lead to iron toxicity.

Interactions between medications and iron

Medications that may affect iron status:

• Aspirin and non-steroidal anti-inflammatory (NSAIDs) medications
  • may cause gastrointestinal bleeding which can cause iron deficiency anemia if it occurs over a long term period
• Histamine blockers (Tagamet and Tagamet HB, Pepcid and Pepcid AC, Axid and Axid AR, Zantac)
  • reduce iron absorption by decreasing the acidity of the stomach
• Antacids
  • reduce iron absorption by decreasing the acidity of the stomach
• Neomycin
  • this antiobiotic reduces iron levels
• Stanozolol
  • this synthetic anabolic steroid related to testosterone is associated with iron depletion
• Warfarin (Coumadin)
  • iron binds to this medication which may decrease the minerals absorption or activity
• Birth control pills (oral contraceptives)
  • as these reduce the amount of blood lost during menses, women who consume sufficient dietary iron may have high blood iron levels

   

Medications whose absorption may be impacted by dietary iron, especially iron-containing supplements:

• Sulfasalazine
  • iron binds with this medication, decreasing its absorption
• Tetracycline
  • iron decreases its absorption
• Thyroid hormone medications
  • iron supplements may decrease their absorption
• Carbidopa
  • iron supplements may interfere with the action of this medication used in the treatment of Parkinsons disease
• Methyldopa
  • iron supplements decrease the absorption of this drug used to lower blood pressure in individuals with hypertension

   

Medications which are used to treat iron intoxication and chronic iron overload:

• Pencillamine
• Deferoxamine (Desferal)

 

Interactions between iron and other nutrients

Vitamin C, copper, cobalt and manganese are among the nutrients that increase iron absorption. Since amino acids stimulate hydrochloric acid secretion they can also improve iron absorption while high intakes of dietary calcium may reduce absorption.

Health conditions that require special emphasis on iron

Individuals who have the following health conditions should pay special attention to their iron status:

• Alcoholism
• Attention deficit disorder
• Colitis
• Diabetes
• Excessive menstrual blood loss
• Gastric ulcers
• Iron deficiency anemia
• Leukemia
• Parasitic infections
• Restless leg syndrome
• Tuberculosis

Forms in which iron is found in dietary supplements.

In dietary supplements, iron is typically available as ferrous sulfate, ferrous fumarate and ferrous succinate.

Foods that are concentrated sources of iron

Excellent food sources of iron include blackstrap molasses, cinnamon, parsley, spirulina, Swiss chard, thyme, tofu and turmeric. Very good sources include asparagus, Brussel sprouts, lentils, mustard greens, pea pods, turnip greens and venison. Calfs liver and beef are considered good sources since they provide iron but do so at a higher caloric concentration that the foods listed above.