iron Flashcards
iron is an essential type of what
mineral or trace element
why is iron in excess bad
cos its extremely toxic as it reacts readily with oxygen
what is the most common nutritional deficiency worldwide
iron efficiency anaemia (500-600 million).
what 2 basic forms is iron found in
haem or non-haem
what is haemoglobin( Hb)
a type of haem protein
Component of red blood cells and transports oxygen round the body
what is myoglobin and wheres it found
Oxygen-transporting protein of muscle (similar to haemoglobin in function)
is in certain skeletal muscle cells storing oxygen for when muscle requires oxygen for aerobic respiration during exercise and muscle contraction
what form of iron do animal products have
haem form
what form of iron do plant products have
non haem form
This form is less efficiently absorbed
what is Ferrous Iron (Fe 2+)
reduced form - most commonly found in food.
what is Ferric Iron (Fe 3+)
Oxidised form - to be bound to transferrin for transport.
what is haem
A chemical complex with a central iron atom that forms the oxygen binding part of haemoglobin and myoglobin.
what is haem iron
Iron found in haemoglobin and myoglobin of animal foods.
what is non haem iron
Iron in plants and in animal foods that is not part of haemoglobin or myoglobin.
what are the 2 valency states iron exists in
Fe 2+ or Fe3+
explain how the oxidised and reduced form of iron can be produced by REDOX
The reduced form Fe2+ can be oxidised into the oxidised form Fe3+. Oxidised form Fe3+ can be reduced into reduced form Fe2+
how do we mask irons presence
by binding it onto proteins
what is transferrin
Protein synthesised in the liver. It transports iron in the blood to erythroblasts to make haem.
it is a transport protein
what is ferritin
Major storage form of iron - a complex of iron and apoferritin.
whats it called when no protein is bound to ferritin
apoferritin when no iron protein bound to it. But when is bound its called ferritin
tissues take oxygen from haemoglobin for what
aerobic respiration
what is the total iron in the body of men and women and why the difference
~3800mg in men and ~2300mg in women.
Men have more iron than females as are more muscular and cos have larger blood circulation volume so more red blood cells
what percentage of iron in the body in haemoglobin is in erythrocytes (red blood cells)
60-70%
what percentage of iron in the body is in muscle myoglobin
10%
what percentage of iron in the body is in storage pools in liver and reticulo-endothial (macrophage) system as ferritin (in liver)and haemosiderin (in macrophages in blood)
20-30%
what percentage of iron in body is in iron containing enzymes
1%
what percentage of iron in the body is in plasma transport pool bound to transferrin.
< 0.2%
there is constant recycling between what
functional and non-functional pools
erythrocytes have a lifespan of what
120 days
haemoglobin is not a storage from of what
iron
what are the functions of iron
Oxygen transport and storage - haemoglobin and myoglobin.
Iron containing enzymes, particularly those involved in energy metabolism and energy production, e.g. cytochromes, NADH dehydrogenase, as well as enzymes used in metabolism and storage.
Immune function – necessary for optimal immune function.
Pro-oxidant activity, is potentially harmful as free radicals damage body. Disturbances in iron metabolism may be pathogenic.
whats the function of haemoglobin and of myoglobin in oxygen transport and storage
Haemoglobin (Hb) - transports oxygen round the body.
Myoglobin - stores oxygen in muscles and tissues.
explain oxygen transport and storage
Iron is stabilised in ferrous (Fe 2+) state in haem complex.
Interaction with adjacent globin protein allows it to bind reversibly with oxygen.
Allows oxygen (also potentially toxic) to be safely distributed and stored round the body.
Haemoglobin also binds CO2 and transports it to lungs for exhalation.
name some dietary sources of haem iron
Food of animal origin
Liver
Red meat
Poultry
Fish
name some dietary sources of non haem iron
Animal and plant tissues
Cereals
Vegetables
Nuts
Eggs
Fish
Meat
(Fortified foods)
SACN (2010) concluded that reducing total red meat consumption of high consumers down to 70g/d would have little effect on proportion of adults with iron intakes <LRNI
name some meat, cereal, fruit and veg, and dairy sources that are high in iron
meat:
black pudding
liver
chicken
pate
venison
cereal:
fortified bran flakes
fortified cocopops
fruit/veg:
legumes
lentils
dairy:
eggs
what does absorption mean
uptake of a nutrient into the intestinal mucosa and its transfer into the body.
what does bioavailability mean
proportion of a nutrient that is taken up and transferred by the intestinal mucosa.
what is the most bioavailable form of iron
haem iron
20-30% absorption from haem containing foods
1-10% absorption from non-haem sources
how many mg/d of iron absorbed from the diet is used to replace lost iron
1mg/d
what does hepcidin mean
principal regulator of iron absorption (a peptide).
explain hepcidin in terms of iron stores
Acts by directly binding to and degrading the iron exporter molecule on the cellular membrane and prevents iron from leaving the cell.
When iron stores are adequate/high, hepcidin production increases.
When iron stores are low or requirements are increased, hepcidin production decreases.
If hepcidin regulation is defective iron overload may result.
what percentage of absorption means deficiency
40%
If no deficiency, ~15%.
what is iron absorption enhanced by
by stomach acidity, but reduced by achlorhydria (decreased acid production in stomach) and antacids.
explain the haem iron absorption in meat
Haem iron in meat is 40% total Fe
of which 15-35 % is absorbed.
relatively little affected by diet.
what are some inhibitors of non haem iron absoption
Phytates (wholegrain cereals, seeds, nuts)
Polyphenols, e.g. tannins (tea, coffee, cocoa, red wine)
Oxalate
Phosphorus
Calcium
Soy protein
what are some promotors of non haem iron absorption
Ascorbic and citric acids (ferric => ferrous)
Cysteine peptides in meat
Iron homeostasis maintained to minimise risk of what
iron toxicity
Absorption of iron from GI tract regulated by what
systemic need.
Risk of damage by free reactive iron limited by what
series of organic molecules which bind free iron and carry it to functional sites or to storage depots.
The main pool of ferritin is in the what and what does it act as
liver which acts as a buffer pool for iron excess to requirements - 25% of body iron.
Iron turnover driven by what
formation of and destruction of haemoglobin in erythrocytes (life span 120 days).
in iron metabolism what is engulfed and destroyed by macrophages.
Senescent erythocytes
in metabolism of iron, iron is released and incorporated into what
into transferrin.
in metabolism where does transferrin take iron to
takes iron to erythroblasts of bone marrow to make new red blood cells.
in the body where does transferrin transport iron to and why
Transferrin transports iron to tissues for the synthesis of haem or storage in ferritin and haemosiderin.
it also transports iron into muscle, bone, and liver
what does homeostasis mean
property of a system to maintain balance or functioning within a normal range.
describe excretion paths for iron
No defined excretory paths.
what does Intestinal uptake and transfer of iron =
iron losses & iron needed for growth & reproduction.
Losses have to be replaced by dietary intake.
whats are ex of iron losses
menstruation
Bleeding or blood donation
Hookworm - infestation determined by total egg count
what are the iron requirement values for during pregnancy
total basal 240 mg
+ blood 500mg
+ foetus and placenta 300mg
what are the iron requirements needed in breast milk
0.25-0.34 mg/day
why do children need iron
fir growth
what is the iron requirement in blood donation
200mg (0.5mg Fe/ml)
what are supply’s of iron
Food iron content
Type of iron
- haem
- non-haem
Absorption
- promoters
- inhibitors
what are some times when iron is required
Growth
Pregnancy
Lactation
iron is metabolised from what
stores
what are the DRVs of iron for males
EAR 8.7 mg, RNI 11.3 mg.
what are the DRVs of iron for menstruating women
EAR 11.4 mg, RNI 14.8 mg.
Losses in menstruation are not normally distributed and RNI not for 10% of women with highest menstrual losses.
describe the process of iron deficiency development
starts with normal cells
decrease in iron stores
decrease in iron transport
(iron deficiency starts to develop)
fall in haemoglobin synthesis
anaemia
what are causes of iron deficiency in uk
Menstruation, 25%
Aspirin/NSAID use, 13%
Colonic carcinoma, 8%
Gastric carcinoma, 5%
Benign gastric ulceration, 5%
Angiodysplasia, 5%
Coeliac disease, 5%
Blood donation, 5%
other 29%
what is iron deficiency anaemia and its affects
Haemoglobin concentration below age-appropriate range for healthy people.
Due to iron deficiency.
Responds to iron repletion.
Effects
Reduced size and haemoglobin
density of erythrocytes.
- Microcytic and hypochromic RBC
what are common symptoms of iron deficient anaemia
Tiredness and lethargy (lack of energy)
Shortness of breath
Heart palpitations (noticeable heartbeats)
Pale complexion
what are less common symptoms of iron deficiency anaemia
headache
Tinnitus
Altered sense of taste
Feeling itchy
Sore orabnormally smooth tongue
Hair loss
Pica
Difficulty swallowing (dysphagia)
Painful ulcers on corners of mouth
Spoon-shaped nails (koilonychia)
whos most at risk of iron deficiency
Infants over 6 months, toddlers and adolescents.
Menstruating women.
Pregnant women.
Older people.
People consuming diets low in iron and high in iron absorption inhibitors like phytate.
Individuals with high blood losses.
explain iron deficiency treatment
Aim:
Restore haemoglobin levels and red cell indices to normal, and to replenish iron stores.
Address underlying causes.
Ferrous sulphate 200mg tablets 2-3 times/day (3 months).
Or ferrous fumarate / ferrous gluconate tablets
If dietary deficiency is thought to be a cause, advise on iron-rich foods and consider referral to dietitian.
Monitor patient to ensure adequate response to treatment.
explain acute and sub chronic iron toxicity
Tends to occur in children – accidental ingestion of supps.
High doses of 50-220mg/d can cause GI effects: nausea, constipation, abdominal pain, diarrhoea and vomiting.
explain chronic toxicity of iron - haemochromatosis
Autosomal recessive genetic disorder
Occurs in 1 in 300.
Unregulated dietary absorption with gradual accumulation of iron in tissues. Leads to irreversible tissue damage.
