Mineral metabolism
Elements are the basic components of the world of living and inanimate matter. Nitrogen (N), sulphur (S), oxygen (O), hydrogen (H) and carbon (C) are components of organic compounds: proteins, carbohydrates, fats and vitamins.
From among 104 well-known elements about 1/3 it are essential for living organisms. They are structural elements of the skeleton and soft tissues, and also regulating factors of many physiological functions, for example coagulation of the blood, transportation of oxygen, activation of enzymes.
These elements can be divided into three groups:
- essential elements, the so-called bio-elements
- neutral elements, without which metabolic processes can occur undisturbed
- toxic elements, harmful for the organism.
Essential elements are classified as macro - and microelements.
Microelements are the elements present in body fluids and tissues in the concentration exceeding 1 µg/g of wet tissue (µg - one millionth part of a gram -10-6g). These are: chlorine (Cl), phosphorus (P), magnesium ( Mg), potassium (K), sodium (Na), calcium (Ca).
Microelements are the elements present in body fluids and tissues in the concentration below 1 µg/g of wet tissue. These are: arsenic (As), chromium (Cr), tin (Sn), zinc (Zn), fluorine (F), iodine (I), cobalt (Co), silicon (Si), lithium (Li), manganese (Mn), copper (Cu), molybdenum (Mo), nickel (Nor), selenium (Se), vanadium (V), iron (Fe).
Toxic elements, harmful for health, are in the first place aluminium (Al), mercury (Hg), cadmium (Cd) and lead (Pb).
Harmfulness of chemical elements depends on various factors, but most important are: concentration of a given element in the body and period of exposure to its activity. The ability of the body to eliminate toxic elements is an important one; the organs involved in this function are the kidneys, liver and alimentary tract. Harmful effect of toxic elements depends on the ability of the organism to repair their toxic effect. Such protective and defensive part can be played by vitamins.
Toxic elements tend to accumulate in parenchymatous organs, in particular in the liver, kidneys, pancreas. At prolonged exposure to toxic elements they may also accumulate in other tissues, for example lead and aluminium in bones, lead, mercury and aluminium in the brain tissue, and cadmium in the hair bulbs.
Progress in science and development of technology has made the methods of quantitative evaluation of elements more and more specific and exact. High sensitivity characterises absorption atomic spectrometry (ASA), spectrometry of atomic emission with excited plasma (ICP-AES), or neurone activation technique (NAA). Modern analytic equipment permits analysis of concentrations of many elements from one sample. It makes it possible to measure many elements in a short time from a small quantity of material, which is important in biological tests.
The content of elements can be determined in body fluids: blood, serum, urine, cerebro-spinal fluid or in tissues. It should be noted, however, that the content of elements in serum or in blood does not reflect current concentrations of these elements in the body, because of equalising mechanisms which maintain the same concentration of elements in the blood on the expense of tissue reseves. Thus, in spite of seemingly correct concentration in serum, the content of elements in the body can be insufficient. The concentration of elements in the blood is directly affected by, for example, presently used diet.