Welcome to Seminar on Iron

Meera Kaur, PhD, RDAssistant Professor

Department of Family MedicineFaculty of Medicine

kaur@cc.umanitoba.cahttp://home.cc.umanitoba.ca/~kaur

Outline• Learning Objectives• Introduction• Physiochemical Properties• Functions• Food Sources• Absorption• Recommended Dietary Allowances• Deficiency• Toxicity• Conclusions• Questions and Answers

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Learning Objectives

• Physicochemical properties• Biological functions• Metabolism• Food sources and Dietary Reference Intakes • Deficiency and toxicity

– The global scenarios

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Introduction

• Iron, one of the most abundant metal on earth, is found in every living cell

• Total body content of iron is 5g

• About 2/3rd of iron in the body is found in hemoglobin (Hb)

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Physiochemical Properties• Pure iron is lustrous, silvery and easily rusts in

damp air

• Solid at 200C

• Melting point: 15350C or 27950F

• Conducts heat and electricity and forms positive ions in its chemical reactions

• Pure iron is fairly soft and can easily be shaped and formed when hot

• Soluble in low pH (acid medium)

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Functions of Iron...

• Iron plays important role in– Immune function– Cognitive development– Temperature regulation – Work performance

Other physiological functions of iron are…

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Functions of iron...

• Iron is important constituent of body protein…– hemoglobin

• gives ability to carry O2 from lung to all tissues

• assists in the transport of CO2 back to lungs for expiration

• How O2 carrying capacity of blood is regulated?

– When the O2 carrying capacity of blood is declined, kidney produces a hormone—Erythropoietin, which targets bone marrow to produce more red blood cells (RBC) and stimulates RBC release from the bone marrow

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Functions of iron...

• Iron is important constituent of body protein…– myoglobin

• provides Oxygen to skeletal and heart muscle

• Acts as a cofactor for many biological reactions– Cytochrome: in Electron transport chain helps transport

electron to molecular O2

– Cytochrome P-450: Oxidative degradation of drugs– Mitochondria: helps conversion of citrate to isocitrate,

the first step of energy production in the body

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Functions of iron...(cofactor)– works with other enzymes to synthesize collagen,

neurotransmitters(dopamine,epinephrine,nonepinephrine, serotonin) and eicosanoid

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Iron works through life cycles

Food Sources• Two forms of dietary iron: Heme and Nonheme

– Heme: Food from animal origin (meat, fish, poultry etc.)• absorbed better than the nonheme iron

– Nonheme: grains and food from vegetable origin (cereal, legumes, vegetables, molasses, blackstrap etc.)

• most dietary iron is nonheme iron that are bound to some other organic constituent of the food.

• Cooking tends to break these interactions and increase iron availability.

Please refer to the handout for food sources of heme and nonheme iron

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Absorptions…• Body uses variety of mechanisms to absorb and

distribute iron in the body

• Heme iron absorbs directly into the absorptive cell– Intestinal mucosal cells in the duodenum and upper jejunum

absorb the iron.

– Heme iron is better absorbed than non heme iron

– Low pH enhances iron absorption

– Phytates, tannins and antacids block iron absorption.

– No physiologic mechanism for excretion of excess iron from the body other than blood loss (i.e., pregnancy, menstruation or other bleeding.)

– Mucosal block and hemosiderin will prevent iron toxicity.

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Factors affecting iron Absorption…Increases Absorption Decreases absorption

– Gastric acid, Low pH – Phytic acid (dietary fiber)

– Heme form of iron – Oxalic acid (leafy veg)– High body demand – Polyphenol (tea, coffee)– Low body stores – Full body stores of iron– Meat Protein Factor – Excess of Zn, Mn, Ca– Vitamin C – Reduced gastric acid

output

– Some antacids

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Absorptions 13

Fe+++

Fe++

Stomach

Mucus membrane

Small Intestine (Duodenum and Jejunum)

Brush border ofAbsorptive cells

Fe+++

Fe +++ + MBP

Absorptive cells

Iron+ ApoferritinStored as Ferritin

LiverCeruloplasmin

MBP

Mucosal Block

Iron + Transferrin

Blood

Cell membrane of brush border

Endocytosis

Receptor cell Lysosome Free iron Various sites

If excess ironHemosiderinBinds ironReduces iron toxicity

Recommended Dietary Allowances(mg/d) Age Males Females Pregnancy Lactation

0 to 6 months 0.27* 0.27* (* Adequate intake)

7 to 12 months 11 11 N/A N/A

1 to 3 years 7 7 N/A N/A

4 to 8 years 10 10 N/A N/A

9 to 13 years 8 8 N/A N/A

14 to 18 years 11 15 27 10

19 to 50 years 8 18 27 9

51+ years 8 8 N/A N/A

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Deficiency…

• WHO considers iron deficiency to be the number one nutritional disorder in the world

• Eighty per cent of the world population may be iron deficient, while 30% may have Iron Deficiency Anaemia (IDA)-- also known as hypochromic microcytic anaemia

• IDA can be detected by measuring hematocrit – the % of blood volume occupied by RBC (normal: <34-37%) and the Hemoglobin in blood (<10-11%)

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Deficiency…IDA

• IDA Associated with– Low dietary intake– Inadequate absorption– Excess blood loss– Vitamin A deficiency (helps mobilize Fe from the

storage site), especially common in the developing countries

– Chronic malabsorptions such as inflammatory bowel diseases

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Deficiency…

• Who are at risk for developing IDA?– Women of childbearing age– Pregnant women– Low birth weight infants– Older infants and toddlers– Teenage girls– Individuals with kidney failure (on Dialysis)

because failing kidneys cannot produce enough erythropoietin to make RBC in the blood

– Intestinal worm infestation (hook worm etc.)

• YYY

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Deficiency Symptoms…• Symptoms of IDA

– Lack of energy or tiredness– Extreme fatigue and feeling of weakness– Pale skin– Light headedness, headache– Pale skin on the lining of the eyes, the inner mouth

and the nails– Rapid and forceful heartbeat– Low blood pressure with position change from

sitting to standing up

• YYY

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Deficiency Symptoms…• Symptoms of IDA

– Finger nails that become thin, brittle and white may grow abnormally with a spoon-shaped appearance

– Tongue may become sore, smooth and reddened– Decrease in appetite– Shortness of breath during exercise– Decreased immune function and increased vulnerability

to infection– A strong desire to eat nonfoods such as ice, paint or dirt

(a condition called Pica)– Disturbed sleep and abdominal pain

• YYY

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Deficiency (blood picture)…20

These red cells are hypochromic and microcytic due to iron deficiency

Deficiency Symptoms…

• YYY

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Deficiency Symptoms…22

Deficiency Symptoms…23

“Mary - a case study”

Mary, a 14 year old girl, was feeling tired all the time. She had brittle nails and sore tongue as well. She went to her physician. Her physician ordered some blood test. After a week her physician called her back to clinic and prescribed Iron tablet for her. He also advised Mary to eat foods rich in vitamin C.

Q. 1. Why Mary was feeling tired?

Q. 2. Why Mary’s doctor Prescribed Iron tablets?

Q. 3. Why Mary’s doctor advised her to eat foods rich in vitamin C?

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Toxicity/Overload

• Two kinds– Hemochromatosis

• Genetic disorder. Causes liver, heart and other organ damage. Absorbs iron three times more than normal. Common treatments are blood donation and drugs that bind iron. Common amongst Asian/ Asian Islanders

– Hemosiderosis • Accumulation of hemosiderin (insoluble storage iron due

to frequent blood transfusion or long-term consumption of large amount of iron. Can affect lung, liver, heart and other vital organs

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Conclusions• Iron -- an important trace mineral

– is needed by everybody throughout the life cycles– Is absorbed in the duodenum and jejunum – is part of hemoglobin and myoglobin that carry oxygen

throughout the body. – carries many other important physiological functions– is stored in liver, spleen and other tissues and it is an

essential part of many of body's proteins and enzymes. – deficiency of which causes Iron Deficiency Anaemia ─

one of the most common nutritional disorders around the globe.

– that our body cannot excrete if overloaded and results in hemochromatosis and hemosiderosis.

• YYY

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Thank you for attending the class

Any question?

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