Iron is known to have a role in hundreds of enzymes and proteins. Hemoglobin in the red blood cells contains about 2/3 of the body’s iron, with the rest being mostly in the myoglobin or muscles cells. Hemoglobin transports oxygen from the lungs to the rest of the body and myoglobin also stores and releases oxygen to the muscles.
Cellular energy depends on ATP (adenosine triphosphate) that is made in the mitochondria with the help of cytochromes that have heme (iron-containing). Iron is important for certain enzymes:
– Catalase and peroxidase that break down hydrogen peroxide (a reactive oxygen species – ROS).
– Myeloperoxidase in the neutrophils (WBC’s) helps with the destruction of any bacteria the WBC has engulfed.
– Ribonucleotide reductase is vital for DNA synthesis.
The iron storage protein ferritin is made in response to adequate iron, and ferritin is reduced when iron is low.
Several nutrients have important interactions with iron:
– Vitamin A deficiency makes iron deficiency worse.
– Copper seems important for proper iron absorption and transport to the bone marrow and red blood cells.
– Zinc is not well absorbed if a zinc supplement is taken with iron supplements.
– Calcium supplements reduce iron absorption if taken at the same time.
Deficiency of iron is most common in conditions of chronic blood loss (infants consuming cows milk, parasites, H. pylori infections, heavy menstruation) and during times of increased need (pregnancy, infants, young children, adolescents). While some vegetarian diets may be low in iron and the iron in vegetables is harder to absorb – there are plenty of high iron vegetables (see below).
SYMPTOMS OF DEFICIENCY
ANEMIA – the main symptom of iron deficiency is anemia, microcytic (small cells) and hypochromic (pale, with less hemoglobin). Most symptoms of iron deficiency are related to the anemia; fatigue, rapid heart rate, dizziness, headaches, shortness of breath with exertion or at higher altitude, reduced athletic performance and endurance with increased lactic acid production on exertion. As anemia gets worse, you look pale, hands and feet get cold. In children, iron deficiency has been associated with delayed development and lowered IQ, and behavior issues. Restless Leg Syndrome (RLS) has been reported to be related to iron deficiency.
Severe iron deficiency can result in cold intolerance, brittle spoon-shaped nails, sores at the corners of the mouth. Arythmias (irregular heart beats) and eventually heart failure can occur. Rarely, difficulty swallowing with webs of tissue in the throat and esophagus (Plummer-Vinson syndrome) can occur. Children may be seen with Pica (eating non-food items).
In pediatrics, routine screening by 9 months of age by measuring hemoglobin (Hgb) will detect anemia as an indirect clue to iron deficiency. If no anemia, then most likely the iron status is adequate. I am suspicious that this is inadequate as nearly all children on whom I check more specific iron studies (serum iron, TIBC – total iron binding capacity, ferritin) show significant iron deficiency and typically very low ferritin levels suggesting low iron stores in the body.
Clams (3 oz) 24
Oysters (3oz) 10
Organ meats (3 oz) 5-10
Tofu, soy bean (1/2 cup) 4-6
Bran cereal w/raisins 5-18
Fortified cereals 5-8
Seeds (pumpkin) 1 – oz 4
Beef (3 oz) 3
Beans, lentils (1/2 cup) 2-3
Fish / chicken 1
Prunes / raisins (1.5 oz) 1
TOLERABLE UPPER LIMITS
40-45 micrograms a day for all ages, infants to adults.
The recommended daily allowance (RDA) ranges between 7-18 micrograms a day from age 6 months to adults with 27 micrograms recommended for pregnancy.
SAFETY AND TOXICITY
In children, accidental overdose can be fatal. It is for this reason multivitamins with iron should be locked up and dispensed with care. Acute iron toxicity can occur at doses of 20-60 mg/Kg and death at doses above 200mg/Kg of body weight.
Symptoms of acute poisoning begin with nausea and vomiting, abdominal pain, black or tarry stools from the intestinal bleeding, low blood pressure and weak pulse, difficulty breathing and coma within hours of a severe poisoning. Long term and fatal damage to multiple organ systems can occur in a day or two or be delayed up to 6 weeks if the fatal ingestion doesn’t kill you in hours. This is a medical emergency, and if in doubt, call poison control and get to the nearest emergency room immediately.
The major issues with iron overload occurs in individuals with hereditary hemochromatosis (HH), a genetic condition where iron is deposited in the liver and other tissues due to excessive absorption of iron over years. Genetic tests for HH can now be done and those with this condition would limit iron containing foods and avoid alcohol and acetaminophen. The other common form of iron overload comes from over supplementing (taking too much iron) by those with anemia that is thought to be iron deficiency when in fact it is another cause such as thalassemia or hereditary spherocytosis. It is for this reason that anemia not responding to iron supplementation in 3-6 months should prompt your physician to do iron studies, to confirm that you do indeed have iron deficiency. If the iron studies are normal, a smear and hemoglobin electrophoresis will usually provide the answer.
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