Trace elements are also minerals, and are only called trace elements when they make up less than 0.01% of the body mass of humans. Essentially, trace elements are involved in the formation of enzymes, and they are therefore essential. The most important trace elements are:

• Selenium
• Zinc
• Iron
• Iodine and
• Copper

Furthermore, manganese, molybdenum, boron, chromium and vanadium also belong to the group of trace elements

Selenium

Selenium is an essential trace element, which significantly contributes to the formation of over 20 important proteins. These proteins protect the body against oxidative processes which can damage cells and DNA, and are also responsible for cell differentiation and cell proliferation. In addition to this, they are important for the metabolism of the thyroid gland.
A balanced supply of selenium seems to contribute to a healthy functioning immune system.
Generally German soil contains relatively little selenium, particularly in south Germany. In different countries, the intake of selenium can be very different depending on the composition of the soil. Herring and tuna in particular contain a great deal of selenium.

Zinc

Zinc is the most important component of the immune system and is involved in a variety of functions. Zinc is involved in the composition of over 200 enzymes.
Zinc is equally important in the metabolism of sex hormones such as testosterone, thyroid hormones, insulin, prostaglandins and growth hormones.  
Zinc is also an important exception in the group of heavy metals in terms of its functions.   

Iron

Iron is quantitatively the most important trace element in the human body. A human body contains 3-5g of iron, two-thirds of which is bound to haemoglobin. In this role iron is extremely important because as a component of red blood cells, it enables the transport of oxygen in the blood.
Iron is also a component of important groups of enzymes, and is therefore involved in energy metabolism. In addition to this, iron is involved in the regulation of oxygen and peroxide. The absorption of iron is significantly promoted by the presence of vitamin C.

Iodine

Iodine is an essential trace element, which is above all vital for the formation of thyroid hormones. Thyroid hormones control many important functions of the body. Iodine is also well known as an antioxidant and it traps free radicals.

Copper

Copper facilitates the absorption and activation of iron and therefore promotes the formation of blood. Copper is also involved in the cell-mediated immune response and is an essential factor in the metabolism of pigment. Without copper, melanin cannot be formed. Melanin is a colour pigment which is present in skin and hair.