ESSENTIAL MINERALS AND TRACE-ELEMENTS
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Definitions:
Minerals were originally mined substances. The name mineral is now applied to ores of metals, or to any natural substance that is neither animal nor vegetable. In the nutritional context, the word is applied to certain elements.
Essential minerals are elements with a recommended daily intake of >100 mg/day; the body content amounts to grams.
- Sodium (Na),
- Magnesium (Mg),
- Potassium (K),
- Calcium (Ca) and
- Phosphorous (P)
are all classified as essential minerals.
Trace elements have a recommended daily intake of <100 mg per day. The body content is in mg or µg. It must be possible to demonstrate a specific function for the element, and biochemical/physiological changes if the provision of the trace element is too low. The symptoms of deficiency should disappear with an increase in the supply of the trace element.
- Iron (Fe),
- Iodine (I),
- Chromium (Cr),
- Copper (Cu),
- Selenium (Se) and
- Zinc (Zn)
are all trace elements.
-Shouldn't these be called essential trace elements?
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Photo
Copper sulfate crystal
Ultra trace elements are any mineral element with established, estimated or suspected daily requirement <1 mg per day:
- Arsenic (As)
- Boron (B)
- Fluorine (F)
- Manganese (Mn)
- Molybdenum (Mo)
- Nickel (Ni)
- Silicon (Si)
Functions of essential minerals/trace elements:
Minerals and trace elements have varied functions. They are intimately involved in many enzyme actions, while some are integral components of hormones or nuclear hormone receptors. Minerals and trace elements form part of transport and storage proteins and have structural roles.
- Crucial role in enzyme activity: Fe, Zn, Cu, Se, Mn, Mo
- Hormones: I - component of steroid hormone receptors: Zn
- Membrane structure: Zn, Se
- Specific proteins: Fe in haemoglobin
In particular, the various enzymes that protect against oxidative stress are dependent on trace elements (Fe, Zn, Cu, Mn, Se)
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Some specific roles of essential minerals/trace elements:
- Iron: haemoglobin, myoglobin, cytochromes, various enzymes
- Iodine: component of thyroid hormones T4 and T3
- Selenium: glutathione peroxidases, conversion of T4 → T3
- Zinc: many enzymes, and transcription factors
- Copper: essential for many enzymes, involved in energy metabolism, neuropeptide synthesis, formation of connective tissue
- Chromium: insulin function?
- Manganese: superoxide dismutase etc.
- Molybdenum: sulphite oxidase, xanthine oxidase, aldehyde oxidase.
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Figure
Two zinc finger motives (in transcription factors) - containing two zinc atoms each.