IRON

Dr.V.Saumya, P.G. Biochemistry.

Dietary requirement

Adult man - 10 mg/day.

Menstruating women - 20 mg/day

Pregnant and lactating women - 40 mg/day

Dietary sources –

Jaggery,organ meats(liver,heart), leafy vegetables,pulses, cereals,

dry fruits.

Absorption ,transport and storage –

Iron is absorbed in the upper part of the duodenum.

In healthy individuals only about 10% of dietary iron is

absorbed.Because of poor absorption of iron,the requirement of

iron in diet is about ten times the body’s requirement.

However,in anemic patients and growing children,higher

proportion of dietary iron is absorbed to meet the

increased body demands.

Iron in foods usually occurs in ferric form(fe 3+),bound to

proteins or organic acids.

In the stomach, the fe3+ is released from foods due to the

effect of gastric HCl.

Reducing substances such as ascorbic acid and cysteine

convert ferric iron ( fe3+) to ferrous iron(fe2+).

Iron in the ferrous form is soluble and readily absorbed.

Factors affecting iron absorption :

1.Acidity,ascorbic acid and cyteine promote iron absorption.

2.In iron deficiency anemia,iron absorption is increased .

3.Aminoacids and small peptides favour iron uptake .

4.Phytates (in cereals),oxalates(in leafy vegetables) and

tannins (in tea inhibit iron absorption by forming insoluble

iron salts.

5.A diet with high phosphate content decreases iron

absorption, while low phosphate promotes absorption.

6.Other minerals such as calcium,copper and lead inhibit iron

absorption.

Iron in mucosal cells :

The iron is absorbed into the mucosal cells in ferrous form

and oxidized to ferric form by the enzyme ferroxidase.

F3+ then combines with a protein called apoferritin to form

ferritin.

From the mucosal cells ,iron either enters the circulation or

lost when cells are desquamated.

Transport of iron in the blood :

The iron released from the ferritin of mucosal cells after a

temporary storage enters the plasma in ferrous state.

Here,it is oxidized to ferric form by a copper containing protein

ceruloplasmin which possesses ferroxidase activity.

Ferric iron now binds to an iron binding protein called

transferrin or siderophyllin.

Each transferrin molecule can bind 2 atoms of ferric iron(fe3+).

Transferrin (250mg/dl) can bind with 400 mg/dl of iron in

plasma,this is known as total iron binding capacity(TIBC) of

plasma.

Storage of iron :

Iron is stored in liver,spleen and bone marrow in the form of

ferritin.

In mucosal cells ,ferritin acts as the temporary storage form of

iron.

Hemosiderin is another iron storage protein which accumulates in

the body(spleen,liver), when the supply of iron is in excess of

body demands.

Iron is considered as a one – way element because of its

negligible excretion from the body(1 mg/day) which may occur

through bile,sweat,hair loss,etc.

Iron is not excreted in urine.

Iron differs from all other substances which are either

inactivated or excreted during the course of their

metabolism in body,hence iron is efficiently recycled in

body.

Iron entry into body is controlled at the absorption

level,depending on the body needs.

The periodical blood loss in menstruating women increases

its requirement twice as men,increased demands are

also observed in pregnancy, lactation and in growing

children.

Biochemical functions :

1.The major role of iron in humans is to carry oxygen to

tissues and co2 to lungs ,as part of heme protein that in

turn is part of hemoglobin. Oxygen is also bound by

another iron containing heme protein in

muscle,myoglobin.

2.Iron plays the vital role inmitochondrial electron transport

as component of cytochromes and iron sulphur proteins.

3.As a component p 450 it is associated with detoxifixcation

of xenobiotics.

4.Iron serves as a component of enzyme catalase in RBC.

Disease states :

1.Iron deficiency anemia :

It is the most common nutritional deficiency disease in the developing

countries. It also occurs due to increased blood loss or defective

absorption.

Occurs in growing children ,adolescent girls and women due toi repeated

pregnancies due to increased physiological demands coupled with

inadequate intake.

Strict vegetarins are prone because of presence of inhibitors of iron

absorption (phytates,oxalates).

It is characterized by microcytic hypochromic anemia with low Hb levels..

Other features include apathy (dull and sluggish), fatigue,pallor, retarded

growth and loss of appetite.

2. Hemosiderosis:

It is a less common disorder characterized by iron overload in body.

It is produced by excessive intake or increased absorption or by excessive

turnover of RBC.

It is commonly observed in persons receiving repeated blood transfusions

over years as patients of hemophilia,hemolytic anemia.

3.Hemochromatosis :

Rare condition may be hereditary or acquired ,the amount of iron is

abnormally increased.

The excessive iron is deposited in the tissues( as liver, spleen,pancreas and

skin).Fe deposition under skin gives it a characteristic bronze

pigmentation, hence the name hemochromatosis.when diabetes,cirrhosis

occur along with hemochromatosis, the condition is referred as bronze

diabetes.