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Trace Elements ("An oligarchy of catalytic elements dominating…
Trace Elements ("An oligarchy of catalytic elements dominating enormous masses of passive elements" — Gabriel Bertrand)
History & Discovery (Antiquity to Bertrand)
ANTIQUITY
Silver water preservation
Zinc for wounds
Sulfur for skin
RENAISSANCE
Paracelsus listed 7 therapeutic metals
MIDDLE AGES
Basil Valentine treated goiter with iodine (essential for thyroid)
SCIENTIFIC TURNING POINT
1894: Gabriel Bertrand at Pasteur Institute coined term "oligo-elements" (biocatalysts, not impurities)
Definition & Classication : <1 mg/kg, WHO 15 & Cotzias Criteria
Definition & 15 WHO Essential Elements
Required in tiny amounts (<1 mg/kg body weight)
Core 15 (WHO): Iron, copper, iodine, zinc, fluorine, cobalt, molybdenum, manganese, selenium, chromium, vanadium, tin, lithium, nickel, silicon
The Paradox (COtZIAS Criteria & Toxicity)
Essentiality Criteria: Constant tissue levels, deficiency causes specific syndromes, reversal by supplementation alone
Toxicity & Interactions: "The dose makes the poison." Excess zinc causes copper deficiency; individual vulnerability
Biological Functions (Enzymes, Hormones & Defense)
Protein Binding
Rarely free; bound to albumin or specific proteins
Enzyme Cofactors
Metalloenzymes (strong, stable incorporation)
Direct electron/atom transport (e.g., Copper in cytochrome c oxidase)
Hormonal Action
Iodine in thyroid hormones
Zinc in insulin
Host Defense & Structure
Structural support (Fluorine in bones/teeth; Silicon in collagen)
Vitamin structure (Cobalt in B₁₂)
Antioxidants (SOD, Catalase, Glutathione peroxidase)
General Metabolism (Sources, Transport & Excretion)
ABSORPTION
Free, bound to small soluble molecules, or specific membrane transporters & active ATP pumps
DIETARY SOURCES
Whole grains, seafood, liver, meat, green vegetables, oilseeds
BLOOD TRANSPORT
Bound to non-specific proteins (albumin) or specific proteins (transferrin, etc.)
TISSUE UTILIZATION & EXCRETION
Utilization: Nervous, skeletal, immune & cardiovascular systems
Storage: Liver (+++), kidneys (++), bone (+), via ferritin or metallothioneins
Excretion: Liver/Bile (Cu, Fe, Mn, Ni), Kidneys/Urine (Cr, Co, Se, Mo, I, F), Sweat