Mineraler och spårämnen - Kap 9 Flashcards
Total body iron content
approximately 3 – 5 g
60% - haemoglobin
25% - storage in the liver
Vad gör järn?
Functions:
• transport of oxygen and electrons
• a component of several tissue enzymes such as
cytochromes that are critical for energy production and
enzymes involved in the immune system
Var finns järn?
Haem iron • primarily from hemoglobin and myoglobin in animal protein sources • readily bio-available, since it is absorbed intact within the porphyrin ring • not influenced by most inhibitory factors in the diet.
• in enriched cereals and pasta, beans, and dark green leafy vegetables • must be solubilized and hydrolysed before absorption is possible • markedly affected by inhibitory ironbinding ligands • enhancers : animal protein, copper, and vitamin C • Inhibitors: vegetable protein, phytic and oxalic acids, zinc, calcium, tea, coffee
Hur tas järn upp?
Heme: taken up by heme carrier protein (HCP) into an intestinal intracellular vesicle Acted on by heme oxygenase to release iron Non-heme: Fe3+ reduced to Fe2+ by duodenyl cytochrome B (DCYTB) in the intestinal lumen and taken up by divalent metal transporter (DMT1)
Iron deficiency
Anemia - – pathologic condition, accompanied by decrease in the
level of hemoglobin and the quantity of erythrocytes per unit of
volume of the blood
Iron overdose
• Severe iron overdose can cause acute hepatic necrosis and lead to multiorgan
failure and death
• Fatal dose – 180-300 g/kg of body weight
Total body zinc content approximately
2 – 3 g
60% in muscles
30% in skeleto
the second most abundant trace metal in the human body
zink - Function:
• In the human body, there are more than
300 different enzymes that require zinc to
function normally! (superoxide dismutase,
alcohol dehydrogenase…)
Zinc in food
• Zinc from animal and plant-originated food are mainly incorporated into the organic molecules (proteins) • Some zinc is present in inorganic forms (in some plant foods) • No evidence for separate ways of absorption
Zinc absorption
- Absorbed in the small intestine
- Release to blood bound to albumin
- High intake of zinc induce synthesis of metallothionein
- Enhancer of zinc absorption:presence of animal protein
- Inhibitor of zinc absorption: phytate
Total body copper content approximately
50 – 120 mg
40% in muscles 15% in liver 10% in brain 6% in blood
coppar - Function:
Part of enzymes - cuproenzymes (participate in redox
reactions)
Examples: amine oxidase, superoxiddismutase, multi-copper
oxidases —ceruloplasmin, hephaestin and zyklopen
Role of copper in iron metabolism
• Copper-containing ceruloplasmin is required for iron
transport to the bone marrow for red blood cell formation
• Ceruloplasmin was first purified from blood plasma by
Holmberg and Laurell in 1948
The intake of copper in the Nordic
countries
varies between 1.0 mg/d
and 2.0 mg/d
Var finns coppar?
beef lever, mörk choklad, apricots, sunflowerseed
The major sources of excess copper are:
• Copper water pipes, especially when attached to a
water softening system - överdos
Factors influce copper absorption
Excess of iron Excess of zinc Some aminoacids (histidin, cysteine) Presence of citrate
Total body manganese content approximately
10 – 20 mg Higher concentration in bone and in organs rich in mitochondria, such as the liver, pancreas, and kidney Low in muscles and plasma
Function:
mangansese
• Catalytic cofactor for arginase, pyruvate carboxylase, and
mitochondrial superoxide dismutase (SOD).
• A specific or unspecific activator for a large number of
other enzymes, some of which participate in the
synthesis of proteins, mucopolysaccharides, and
cholesterol.
Manganese absorption
• Only about 3 – 5% of an ingested dose is absorbed
• Gender differences in Mn absorption, men absorbing significantly
less Mn compared to women probably due to higher serum ferritin
concentrations in men
Manganese deficiency
• Only in experimental animals (changes in
skeleton, slow growth, fatty liver)
Manganese overdose
• From excess respiratory or dietary
exposures
• Neurotoxicity - oxidativ stress, inhibition av complex 1 i elekrontransportkedjan
Total body selenium content approximately
13 – 20 mg
• 30% is in the liver, 15% in kidney, 30% in muscle, 10% in blood plasma
Selenium functions
• Part of enzymes
• Co-factor in antioxidant activities and thyroid hormone
metabolism
Selenium absorption and metabolism
• Selenium in food is mainly in organic form
• Selenium absorption does not appear to be under homeostatic control
For example, absorption of the selenite form of selenium is greater than
80% whereas that of selenium as selenomethionine or as selenate may
be greater than 90%
• Therefore, the rate-limiting step determining the overall availability of
dietary selenium is not likely to be its absorption but rather its
conversion within tissues to its metabolically active forms
Selenium deficiency
• Selenium deficiency is rare
• Selenium deficiency may contribute synergistically
with iodine deficiency to the development of goiter
and hypothyroidism
• In China, growing children with selenium deficiency
may develop chronic osteoarthropathy (Kashin-Beck
disease).
• Diagnosis of selenium deficiency is made clinically or
sometimes by measuring glutathione peroxidase
activity or plasma selenium, but neither of these tests
is readily available.
Selenium overdose
• In areas with high levels of selenium
• Symptoms of selenosis: garlic odor on the breath, gastrointestinal
disorders, hair loss, sloughing of nails, fatigue, irritability, and
neurological damage.
• Extreme cases of selenosis can result in cirrhosis of the liver,
pulmonary edema, and death.
• Exceeding the Tolerable Upper Intake Level of 300 micrograms
per day
Cobalt - funktion och källa
Part of Vitamin B12 (cobalamin)
Meat, liver, kidney, clams, oysters, and milk
all contain some cobalt. Ocean fish and
sea vegetables have cobalt, but land
vegetables have very little; some cobalt is
available in legumes, spinach, cabbage,
lettuce, beet greens, and figs.
Cobalt overdose
• Toxicity can occur from excess inorganic cobalt found as
a food contaminant.
• Beer drinker’s cardiomyopathy (enlarged heart) and
congestive heart failure have been traced to cobalt
introduced into beer during manufacturing. Increased
intake may affect the thyroid or cause overproduction of
red blood cells, thickened blood, and increased activity in
the bone marrow.
• Deficiency of cobalt is not really a concern if we get
enough vitamin B12.
Vilka andra finns?
Chromium
Fluoride
Iodine
