Iron

Question 1

Iron

Answer 1

• Iron is the most abundant element on earth.
• It plays a crucial role in the biosynthesis of chlorophyll and production of haemoglobin
• It exists in several oxidation states, however, the only two forms present in the human body are: Ferrous (Fe2+) and Ferric (Fe3+) iron.
The ferrous state is needed for absorption.
• The bone marrow uses large quantities of iron to produce erythrocytes.
• We have between 3-4g of iron in our bodies distributed throughout blood, bone marrow, muscles, and enzymes.

Question 2

Iron: Food Sources

Answer 2

• There are two dietary forms of iron:

• Non-haem iron (plant and animal foods) ferric form of iron.
• Haem iron (animals: meats, poultry, fish) ferrous form of iron.

Grains: quinoa (9.25mg), amaranth, rye, oats
Legumes: soybeans (5.14mg), lentils, chickpeas, kidney
Vegetables: spinach (2.71mg), swiss chard, rocket
Nuts & Seeds: pumpkin (14.97mg), sesame, cashew, flax
Meat & Fish: clams (27.96mg), calf’s liver, oysters, prawns, sardines, salmon

Question 3

Iron: Roles

Answer 3

Oxygen transport and storage
Energy (ATP) Production
Endocrine System
Immune Function
Neurotransmitter synthesis

Question 4

Iron: Oxygen Transport & Storage - Functions

Answer 4

• A component of haemoglobin (Hb), which has 4 binding sites for iron. Each iron atom can then bind one oxygen atom. Note that one erythrocyte has 280 million Hb molecules.
• A component of myoglobin (stores oxygen in muscles)

Question 5

Iron: Oxygen Transport & Storage - Therapeutic Uses

Answer 5

• Anaemia
• Fatigue
• Muscle weakness
• Exercise endurance (i.e. sports)

Question 6

Iron: Energy (ATP) Production - Functions

Answer 6

• A component of cytochrome enzymes in the Electron Transport Chain

Question 7

Iron: Energy (ATP) Production - Therapeutic Uses

Answer 7

• Fatigue

* Mitochondrial support

Question 8

Iron: Endocrine System - Functions

Answer 8

• Iron is needed for the activity of the enzyme ‘thyroid peroxidase’, which is required to synthesise thyroid hormones.

Question 9

Iron: Endocrine System - Therapeutic uses

Answer 9

• Thyroid support (hypothyroidism)

Question 10

Iron: Immune function: Functions

Answer 10

• Lymphocyte proliferation and maturation.

Question 11

Iron: Immune function: Therapeutic uses

Answer 11

• Immune support

Question 12

Iron: Neurotransmitter Synthesis - Functions

Answer 12

• A cofactor of tyrosine hydroxylase (converts the amino acid tyrosine to dopamine

Question 13

Iron: Neurotransmitter Synthesis - Therapeutic uses

Answer 13

• Cognition / learning

* Parkinson’s

Question 14

Iron Storage

Answer 14

• Iron that is not used for haemoglobin production is stored in the protein ferritin, which is constantly made and broken down.
• When iron stores are high, the liver converts ferritin into another storage protein hemosiderin , which releases iron more slowly.
• The lifespan of an erythrocyte is 3-4 months , at which stage the spleen and liver dismantle erythrocytes and salvage the iron. This is recycled to make more erythrocytes.
• The body loses some iron daily via the GI tract and when bleeding occurs (only tiny amounts are lost in urine, sweat and shed skin).

Question 15

Iron: Absorption and excretion

Answer 15

• Humans cannot excrete Iron and, therefore, iron levels in the body are regulated by the amount absorbed in the intestine. i.e. Higher levels in tissues → down regulation of gut absorption. Proteins help the body to absorb iron from food:
• Mucosal Ferritin receives iron from food and stores it in the small intestinal mucosal cells.
• Mucosal Transferrin transfers the iron to Blood Transferrin which transports the iron to the rest of the body.
• If the body does not need iron, it is carried out when the intestinal cells are shed and excreted in the faeces (happens every 3 days).
• Iron absorption depends on various factors like GI tract health, the presence of supportive/inhibiting nutrients (e.g. vitamin C / phytates), and the food source (haem v. non haem).
• Haem iron has a higher absorption rate (35%) than non haem iron (2%-20%).
• Non -haem iron absorption is more sensitive to body iron stores:
- In states of iron deficiency, non-haem iron absorption increases.
- In iron overload, non-haem absorption decreases.
• Note: Iron from supplements is less well absorbed than from food, so doses are typically high: Ferrous sulphate / gluconate / succinate.

Question 16

Iron: Absorption of non-haem iron

Answer 16

• Non haem iron absorption is enhanced by:
- Vitamin C a vitamin C dependent enzyme called ‘vitamin C ferrireductase’ embedded in the cell membranes of duodenal enterocytes that converts iron from the Fe 3+ to Fe 2+ state. Just 25mg of vitamin C can improve the bioavailability of non-haem iron by 60% (so a squeeze of lemon juice might be enough!)
- Haem Iron enhances non-haem Fe absorption (i.e. eaten together).
• Non-haem iron absorption is inhibited by:
- Phytates , oxalates and polyphenols
- Calcium & Phosphorus (i.e. dairy)
- Tannic acid (Tea & Coffee)

Question 17

Iron Deficiency

Answer 17

Vulnerable Stages of Life:
• Women of reproductive age (menstrual blood loss)
• Pregnancy (↑ blood volume; blood loss in labour)
• Times of rapid growth (e.g. teenagers)
Iron deficiency anaemia (different from iron deficiency) is a severe depletion of iron resulting in a low haemoglobin concentration.
•Symptoms: Fatigue on exertion, weakness,headaches, apathy, breathlessness, poor resistance to cold temperatures.
Signs: Pallor, nail spooning, hair loss, tachycardia.

Question 18

Iron Defeciency Anaemia: Signs and Symptoms

Answer 18

• Symptoms:
Fatigue on exertion, 
weakness, 
headaches, 
apathy, 
breathlessness, 
poor resistance to cold temperatures.
• Signs:
Pallor, 
nail spooning, 
hair loss, 
tachycardia.

Question 19

Iron: Toxicity

Answer 19

• Iron toxicity is a risk for millions of people because there is no physiological mechanism for iron excretion.
• Non-haem Fe absorption is down regulated when Fe levels in the body are high, but Haem iron is absorbed much more efficiently, and the body has less control over how much it absorbs.
• This can lead to Iron overload which can be harmful, because:
- Free iron is a pro-oxidant and can cause oxidative damage (associated with atherosclerosis, cancer, Alzheimer’s
- Iron is a bacterial growth factor and can cause increased infection rates (hence only 1% of iron in the body is unbound).
- Excess iron can accumulate in organs (e.g. the brain and liver).
Contributors to Iron overload can be:
• Haemochromatosis (a common genetic disorder affecting 1 in 250 individuals that enhances iron absorption).
• Indiscriminate use of iron supplements
• High dose vitamin C supplementation.
• Excessive red meat (haem iron) consumption, which has been linked to greater iron stores and a higher risk of:
- Some cancers (e.g. colon, prostate).
- Diabetes mellitus and Heart disease.

Question 20

Iron: Nutrient Interactions

Answer 20

• Vitamin C enhances the absorption of non haem Fe and also reverses inhibitory effect of some foods on Fe absorption.
• Non-haem iron and Zn compete for a common absorption pathway. Supplementation of one decreases absorption of the other.
• Iron appears to compete with Cu for intestinal absorption.
• High Ca supplementation (or high dairy intake) decreases absorption of non haem iron.