Too much of a good thing can be
detrimental
By Jezabel Olvera
Iron is an essential mineral for normal cellular
physiology, but an excess can result in cell
injury.
Levels of some antioxidants are decreased
during iron overload, a finding suggestive of
ongoing oxidative stress. Reduced cellular
levels of ATP, lysosomal fragility, impaired
cellular calcium homeostasis, and damage to
DNA all may contribute to cellular injury in iron
overload.
MECHANISM
To be absorbed, dietary iron must be in its ferrous
Fe2+ form. A ferric reductase enzyme on the
enterocytes' brush border, Dcytb, reduces ferric Fe3
to Fe2+. A protein called divalent metal
transporter1[DMT1], which transports all kinds of
divalent metals into the body, then transports the iron
across the enterocyte's cell membrane and into the
cell. These intestinal lining cells can then either store
the iron as ferritin or the cell can move it into the rest
of the body, using a protein called ferroportin.
Iron is taken into cells by receptor-mediated endocytosis
of monoferric and diferric transferrin.
These receptors engulf and internalize both the protein
and the iron attached to it.
Ferro-transferrin binds to transferrin
receptors on the external surface of the
cell. The complex is internalized into an
endosome, where the pH is lowered to
about 5.5. Iron separates from the
transferrin molecule, moving into the cell
cytoplasm. Here, an iron transport
molecule shuttles the iron to various points
in the cell, including mitochondria and
ferritin. Ferritin molecules accumulate
excess iron. Lysosomes engulf aggregates
of ferritin molecules in a process termed
"autophagy".
Men and people who are exposed to high levels of iron in
their food, water or occupation, are more susceptible to
iron toxicity. Accidental overdose of iron-containing
products is the single largest cause of poisoning fatalities in
children under 6 years of age. Iron toxicity can come from
a variety of sources. It is found in animal products
especially meats. Shellfish, liver and organ meats are rich
in iron. It is found in kale, collard greens and spinach, but
is not easily absorbed from them. Dried fruits, berries and
nuts are good sources. Acidic foods cooked in iron
cookware will pick up iron from it. Some communities
have iron water pipes which can deposit iron into the water.
Iron supplements not prescribed by a physician can
contribute to iron toxicity. Breads, cereals and other white
flour products contain iron. Beer and wine also contain
iron.
Toxicity
The oral dose of elemental iron is approximately 100300 mg/kg of body weight. Considerably less has been
fatal. Symptoms of acute toxicity may occur with iron
doses of 20-60 mg/kg of body weight. Iron overdose is
an emergency situation because the severity of iron
toxicity is related to the amount of elemental iron
absorbed.
Acute toxicity
• Within 1-6 hours of ingestion, symptoms may include
nausea, vomiting and abdominal pain, tarry stool, lethargy,
weak and rapid pulse, low blood pressure, fever, difficulty
breathing and coma.
• If not fatal, symptoms will subside for 24 hrs.
• Symptoms may return 12 to 48 hrs. after ingestion and
may include signs of failure in cardiovascular, kidney,
liver, blood and central nervous system.
• Long term damage to the central nervous system, liver and
stomach may develop 2-6 weeks after ingestion.
Long term over consumption
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Most often diagnosed after tissue damage has occurred.
Enlarged liver
Skin pigmentation
Lethargy
Joint diseases
Loss of body hair
Amenorrhea
Impotence
The list is extremely long. Many diseases are caused by
high iron consumption.
Synergists
Iron absorption is enhanced by the amino
acids histidine, lysine and vitamin C,
vitamin E, citric acid, lactose, fructose,
glucose, sucrose, and sorbitol. Ingestion
of acidic foods such as; alcohol and
animal proteins, enhances iron absorption.
States of anemia, B6 deficiency, iron
deficiency and hypoxia also enhance iron
absorption.
Psychological effects of iron
toxicity
• Iron toxicity is commonly associated with
personality characteristics of a strong
ego,rigidity, tenaciousness, hostility
stubbornness and irritability.
• Iron also deposits in the amygdala, a portion
of the brain associated with feelings of
anger and hostility.
Treatment
• The first part of treatment for ingestion of iron is
gastric emptying, but this is only useful if the tablets
were taken less than 4 hours ago. If the tablets were
slow-release preparations and if tablets are left in the
bowel after gastric emptying, then whole-bowel
irrigation may also be performed.
• Deferrioxamine is the chelating agent that is used to
treat iron intoxication. It should be given immediately
if the poisoning is thought to be severe.
• Hepatic, renal, blood and liver function should be
monitored.
Conclusion
Iron is essential in the diet. It is found in many different
foods and other things we use on a daily basis. There is
synergists that enhance its effect in our cells. Long term
exposure to high quantities of iron results in many
diseases. Unfortunately, most who are exposed to high
amounts of iron don’t know it until they experience
symptoms of a particular disease which was caused by
excess iron. For those who take iron supplements
without a doctor’s order, they run the risk of getting iron
toxicity. People who try to eat many foods rich in iron,
are running the same risk of iron toxicity.
Sources
http://www.portfolio.mvm.ed.ac.uk/studentwebs/session2/gr
oup29/index.htm
http://www.drhoffman.com/page.cfm/120
www.food-info.net/uk/min/iron.htm
http://www.arltma.com/IronToxDoc.htm