Trace element

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Trace element (also called micro- element ) is generally called a chemical element that occurs only in low concentrations or in traces; if the concentration is extremely low, it is also referred to as ultra-trace element .

The abundances of chemical elements differ considerably, if you consider their occurrence in the solar system , in planet earth , in rocks of the earth's crust , in the water of oceans or, for example, in the human body . Within the respective frequency distribution, the common elements are separated from the rare trace elements as quantity elements.

While in geochemistry the proportions and accompanying elements of rocks and minerals in concentrations below 0.1% or 1000 ppm are referred to as trace elements , analytical chemistry usually prefers a threshold value of 100 ppm or 100 µg / g (= 100 mg / kg) or 0.01%. The more narrowly defined biological term must be distinguished from this:

In biology, chemical elements are called essential trace elements which are ( essentially ) necessary for a living being - colloquially mostly related to humans - and which occur in the organism in mass proportions of less than 50 mg / kg. At concentrations of less than 1 µg / kg, the term ultra-trace elements is sometimes used. Microelements belong to the group of micronutrients .

Trace elements essential for humans

Too little or even the lack of essential trace elements causes deficiency diseases in living beings . Such deficiency symptoms - such as anemia due to iron deficiency or an enlargement or hypofunction of the thyroid gland due to iodine deficiency - make the indispensability (essentiality) of an element obvious. On the other hand, trace elements - like any substance above a certain dose - can also have detrimental consequences in excessive amounts.

Trace elements are usually ingested when eating and drinking with food that contains them in trace amounts. With reduced intake, increased excretion or increased need, the body may be insufficiently supplied with trace elements. Possible reasons for this are

  • Eating habits - e.g. B. low selection, one-sided preference, special forms of preparation or separation processes of food
  • Regional conditions - for example very little occurrence in arable land or drinking water
  • increased loss, for example from diarrhea or profuse sweating
  • changed conditions for uptake, excretion and need in different metabolic diseases

Medically, iron (Fe) is assigned to trace elements because of its mode of action; humans contain an average of around 60 mg / kg.

Fluorine (F), on the other hand, is not one of the essential trace elements, but fluoride (F - ) has a caries- preventing effect. The Federal Institute for Risk Assessment (2006) recommends an average total amount of 3.1 mg per day as an appropriate fluoride intake for adults, including for pregnant and nursing mothers. A similar value of 0.05 mg / kg body weight for daily intake is recommended by the EU Commission's Scientific Advisory Committee on Food Safety (2013). The daily maximum recommended amount ( Tolerable Upper Intake Level , UL) is 7 mg for adults or 0.1 mg / kg body weight. Excessive fluoride intake can lead to fluorosis of the teeth ( dental fluorosis ) and the skeleton ( osseous fluorosis ).

For a number of trace elements in very low concentrations ( boron , bromine , cadmium , lead , lithium ) it is still unclear whether they only occur as an accidental (“random”) component in humans or whether they have any physiological function.

Collection of trace elements

Trace elements (or ultra-trace elements) essential for humans are:

Trace elements may be essential for humans

element Good source Importance to the body Recommended intake per day
chrome Meat, whole grain products, vegetable oils, beer (in Western Europe steel (processing, cookware) is the most important source) unexplained / controversial, glucose metabolism 20–100 µg (estimate), 30–140 µg
Cobalt Animal products of all kinds Part of cobalamin (vitamin B 12 ), only essential as such 0.2 µg, no recommendation
iron Pork liver, sauerkraut (The spinach recommended earlier has a high iron content, but because of the oxalates and tannins it also contains, this iron can only be absorbed to a small extent. Iron from plant-based foods is generally poorly absorbed due to the simultaneous intake of reducing food components, especially ascorbic acid (Vitamin C) , the absorption rate of vegetable iron can be increased up to seven times.) Part of many enzymes and z. B. of hemoglobin 10-15 mg
Iodine Marine fish, crustaceans, edible algae Part of the thyroid hormones 200 µg
copper Whole grains, nuts, cocoa, some green vegetables, ruminant entrails, fish and shellfish Part of numerous redox enzymes 1-1.5 mg
manganese Black tea, nuts, whole grains and green leafy vegetables Activator and component of numerous enzymes → antioxidative metabolism, cartilage and bone synthesis , gluconeogenesis 1 mg, 2-5 mg
molybdenum Omnipresent (ubiquitous) Part of the universal molybdenum cofactor 50-100 µg
nickel Part of urease , methyl coenzyme M reductase , some hydrogenases , carbon monoxide dehydrogenase 25-30 µg
selenium Animal proteins from farm animals fed with selenium (Central Europe) → eggs, meat Part of 30–50 selenoproteins such as glutathione peroxidase 1.5 µg / kg, 30-70 µg
Silicon Millet, beer essential component of the mucopolysaccharides in epithelia and connective tissue About 1.4 g in the human body. 30 mg
Vanadium Legumes, nuts, seafood various effects in the body, such as stimulation of glycolysis in the liver , inhibition of gluconeogenesis - essentiality unexplained <10 µg
zinc Animal foods, especially cheese, offal, muscle meat, some types of fish and especially shellfish Zinc-dependent enzymes are involved in almost all life processes, e.g. B. synthesis of collagen , thymulin , testosterone or breakdown of alcohol by alcohol dehydrogenase involved 12-15 mg, 7-10 mg

Position in the periodic table of chemical elements:

H   Hey
Li Be   B. C. N O F. No
N / A Mg   Al Si P S. Cl Ar
K Approx Sc   Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y   Zr Nb Mon Tc Ru Rh Pd Ag CD In Sn Sb Te I. Xe
Cs Ba La * Hf Ta W. re Os Ir Pt Au Ed Tl Pb Bi Po At Marg
Fr. Ra Ac ** Rf Db Sg Bra Hs Mt Ds Rg Cn Fl Lv
  * Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho He Tm Yb Lu
  ** Th Pa U Np Pooh At the Cm Bk Cf It Fm Md No Lr
The four basic organic elements Set elements essential trace elements probably essential trace elements

Biological importance for humans


Iron is required by the body, among other things, for building important proteins and for regenerating red blood cells and muscles. Iron deficiency is the most common cause of anemia . This manifests itself initially through rapid exhaustion during physical activity and, in the manifest stage, also through pale, rough skin and brittle fingernails and hair.

Iron is available in sufficient form in many foods. The actual iron content of a food is of secondary importance for iron absorption. What is more important is which foods are combined. This is due to the fact that a number of food components strongly promote or inhibit iron absorption. A combination with vitamin C is particularly beneficial for the absorption of iron from plant sources. On the other hand, substances in coffee, black tea and spinach , for example, formerly wrongly recommended as a good source of iron, inhibit iron absorption particularly strongly.

important sources of iron
Food source Iron content
Pork liver
Chicken egg yolk
Beef liver
Blood sausage
White beans


  • Ivor E. Dreosti: Trace Elements, Micronutrients, and Free Radicals , 1st Ed., Totowa: Humana Press, New Jersey 1991, ISBN 978-0-89603-188-3
  • Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition. Spectrum Akademischer Verlag, Heidelberg 2007, ISBN 978-3-8274-1800-5 .
  • Donald Voet, Judith G. Voet: Biochemistry. 3. Edition. John Wiley & Sons, New York 2004, ISBN 0-471-19350-X .
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  2. a b Federal Institute for Risk Assessment: Maximum levels for boron and fluoride in natural mineral waters should be based on drinking water regulations , BfR Opinion No. 024/2006 of February 7, 2006, p. 13.
  3. ^ A b Opinion of the EU Commission Scientific Advisory Committee on Food Safety, EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA): Scientific Opinion on Dietary Reference Values ​​for Fluoride. In: EFSA Journal. Volume 11, No. 8, August 2013; DOI: 10.2903 / j.efsa.2013.3332 .
  4. Dental fluorosis
  5. Review ( Memento from September 26, 2011 in the Internet Archive ) (PDF; 103 kB) Food Standards Agency (FSA)
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  12. K. Schwarz: New essential trace elements (Sn, V, F, Si): Progress report and outlook. In: Trace Element Metabolism in Animals-2. University Park Press, Baltimore MD 1974, p. 366.
  13. FH Nielsen, HH Sandstead: Are nickel, vanadium, silicon, fluorine, and tin essential for man? A review. In: Am J Clin Nutr , 27, 1974, pp. 515-520, PMID 4596029
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