Minerals - Iron (Fe) Flashcards
Iron (Fe)
- 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:
o Ferrous (Fe²+) iron
o Ferric (Fe³+) iron
o The ferrous state is needed for absorption - The bone marrow uses large quantities of iron to produce erythrocytes
- We have between 3 - 4 g of iron in our bodies distributed throughout the blood, bone marrow, muscles and enzymes
Food sources
- There are two dietary forms of iron:
o Nom-haem iron (plant and animal foods) – ferric form of iron
o Haem iron (animals: meats, poultry, fish) – ferrous form of iron
Food Source / Per 100 g:
Grains: Quinoa, amaranth, rye, oats / 9.25 mg
Legumes: Soybeans, lentils, chickpeas, kidney / 5.15 mg
Vegetables: Spinach, swish chard, rocket / 2.71 mg
Nuts/seeds: Pumpkin seeds, sesame, cashew, flax / 14.97 mg
Meat/fish: Clams, calf’s liver, oysters, prawns, sardines, Salmon / 27.96 mg
Functions: Oxygen transport and storage
Functions: Oxygen transport and storage
* A component of haemoglobin (Hb), which has four 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)
Therapeutic uses:
* Anaemia
* Fatigue
* Muscle weakness
* Exercise – endurance (i.e. sports)
Haem = blood, myo = muscle, globin = a protein
Functions: Energy (ATP) production
Functions: Energy (ATP) production
* A component of cytochromes enzymes in the electron transport chain
Therapeutic uses:
* Fatigue
* Mitochondria support
Functions: Endocrine system
Functions: Endocrine system
* Iron is needed for the activity of the enzyme ‘thyroid peroxidaseIs’, which is required to synthesise thyroid hormones
Therapeutic uses:
* Thyroid support (hypothyroidism)
Functions: Immune function
Functions: Immune function
* Lymphocyte proliferation and maturation
Therapeutic uses:
* Immune support
Functions: Neurotransmitter synthesis
Functions:
* A co-factor of tyrosine hydroxylase (converts the amino acid tyrosine to dopamine)
Therapeutic uses:
* Cognition/learning
* Parkinson’s
Storage
- 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 life span 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)
Excretion
Excretion:
* 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
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 three 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 vs. non-haem).
* Haem-iron has a higher absorption rate (15%-35%) than non-haem(2%-20%)
* Non-Haem iron absorption is more sensitive to body iron stores:
o In states of iron deficiency, non-haem iron absorption increases
o In iron overload, non-haem absorption decreases
* Note: Iron from supplements is less well absorbed than from food; doses are typically high: ferrous sulphate/gluconate/succinate
Ferri = iron
Absorption of
non-haem iron enhancement
Non-haem iron absorption is enhanced by:
* Vitamin C – Vitamin C dependent enzyme called ‘vitamin C a ferrireductase’ embedded in the cell membranes of duodenal enterocytes that converts iron from the Fe³ to Fe² state. Just 25 mg of vitamins 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)
Absorption of non-haem iron inhibition
Non-haem iron absorption is inhibited by:
* Phytates, oxalates and polyphenols
* Calcium and phosphorus (i.e. dairy)
* Tannic acid (tea and coffee)
Optimising non-haem iron intake
How to optimise an individuals intake of non-haem iron:
* Eliminate junk food (nutrient-depleted, highly processed foods)
* Build meals around Fe rich foods, e.g. dark green vegetables, beans, whole grains
* It high vitamin C vegetables and fruit with meals (peppers, cruciferous, kiwis, oranges, lemons) to promote Fe absorption is
* Avoid drinking black tea and dairy at mealtimes
* Eat foods that contain yeast (e.g. bread), are sprouted (e.g. beansprouts), and fermented (e.g. tempeh) to reduce inhibitors like phytates
Iron deficiency: Vulnerable stages of life
Vulnerable stages of life:
* Women of reproductive age (menstrual blood loss)
* Pregnancy (Increased blood volume; blood loss in labour)
* Times of rapid growth (e.g. teenagers)
Iron deficiency anaemia
Iron deficiency anaemia (different from iron deficiency) is a severe depletion of iron resulting in a low haemoglobin concentration:
Anaemia = a deficiency of haemoglobin and hence decreased oxygen transport
