Compendium: Trace Elements
for Skin & Hair

Chapter 1: Structure and Renewal of Skin and Hair

Human skin is the largest organ of the body and covers an average area of 1.7 m² in an adult. It forms a physical barrier against environmental influences, regulates body temperature, and houses sensory receptors for touch, pressure, and temperature.

1.1 The Layers of the Skin

The epidermis, as the outermost layer, consists predominantly of keratinocytes. These cells originate in the basal layer (stratum basale), migrate upward over the course of about four weeks, and become increasingly keratinized in the process. Finally, they are shed as dead horny scales — a process known as desquamation.

Beneath the epidermis lies the dermis, in which fibroblasts produce type I and III collagen as well as elastin. These structural proteins give the skin its mechanical strength and resilience. The dermis also contains blood vessels, nerve endings, and the skin appendages — including the hair follicles.

1.2 The Hair Cycle

Each hair goes through a recurring cycle of three phases:

1. Anagen phase (growth phase): The matrix cells in the hair follicle divide at high speed. On the scalp, this phase lasts between two and six years and determines the maximum hair length.
2. Catagen phase (transition phase): Cell division stops and the follicle shrinks. This phase lasts about two to three weeks.
3. Telogen phase (resting phase): The hair remains in the follicle without active growth until it eventually falls out and a new hair takes its place. This phase lasts three to four months.

During the anagen phase, the rapidly dividing matrix cells require a continuous supply of amino acids, vitamins, and trace elements. The melanocytes in the hair bulb, which give the growing hair its color, also depend on certain cofactors.

Chapter 2: Zinc and the Maintenance of Normal Skin

2.1 Zinc in the Epidermis

The concentration of zinc in the epidermis is five to six times higher than in the dermis. This gradient reflects the importance of zinc for keratinocyte differentiation. As a cofactor, zinc is involved in the activity of metalloproteinases, which control the orderly remodeling of the extracellular matrix.

In addition, zinc functions as a component of Cu/Zn superoxide dismutase (SOD1), an antioxidant enzyme that neutralizes superoxide radicals in the skin. Cell division in the basal layer also requires zinc, as the mineral is needed for DNA polymerase and thymidine kinase.

2.2 Dietary Sources and Bioavailability

The EU reference value for zinc is 10 mg per day. The following table shows selected foods and their zinc content:

The bioavailability of zinc from plant sources is limited by phytic acid. Soaking, sprouting, and fermentation reduce the phytate content and thus increase zinc absorption in the small intestine. Animal protein sources provide zinc in a more readily absorbable form.

Chapter 3: Selenium and the Maintenance of Normal Hair

3.1 Selenoproteins in the Hair Follicle

Selenium is incorporated in the form of the amino acid selenocysteine into at least 25 known selenoproteins. In the hair follicle, glutathione peroxidases (GPx) and thioredoxin reductases (TrxR) are particularly important:

• Glutathione peroxidase (GPx): This enzyme catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water or alcohols, respectively. In the rapidly dividing matrix cells of the hair follicle, increased amounts of H₂O₂ are produced as a metabolic by-product, which is neutralized by GPx.
• Thioredoxin reductase (TrxR): This selenoprotein regenerates oxidized thioredoxin and is thus involved in maintaining the intracellular redox balance. The redox balance affects the signaling pathways that influence the hair cycle.
• Iodothyronine deiodinases (DIO): These selenium-dependent enzymes catalyze the conversion of thyroid hormones in tissue. Thyroid hormones influence the hair cycle, and local conversion in the follicle depends on selenium.

3.2 Daily Requirement and Food Sources

The EU reference value for selenium is 55 µg per day. Selenium levels in foods vary greatly depending on the selenium content of the soils on which the plants grew or the animals grazed.

3.3 Absorption and Metabolism

Organic selenium compounds such as selenomethionine are absorbed in the small intestine via the same transport pathways as methionine and have an absorption rate of over 90 %. Inorganic selenium (sodium selenite) is also well absorbed, but its metabolic pathway differs: it is channeled directly into the selenoprotein synthesis pathway without entering the general methionine pool.

Chapter 4: Copper and Normal Hair Pigmentation

4.1 Melanin Biosynthesis

The color of hair is determined by melanin, which is produced by melanocytes in the hair bulb and released to the surrounding keratinocytes. There are two main types of melanin:

• Eumelanin: Brown to black pigment that predominates in dark hair.
• Pheomelanin: Yellow to red pigment that predominates in blond and red hair.

The rate-limiting step of melanin biosynthesis is catalyzed by the enzyme tyrosinase. Tyrosinase is a copper-dependent enzyme: its active site contains two copper ions, which are required for the oxidation of L-tyrosine to L-DOPA and further to dopaquinone. Without available copper, tyrosinase remains inactive.

4.2 Other Copper-Dependent Processes

In addition to melanin synthesis, copper is also involved in the cross-linking of collagen and elastin, via the enzyme lysyl oxidase. This enzyme links collagen fibrils and elastin molecules in the dermis and thus contributes to the stability of the connective tissue in which the hair follicles are anchored.

4.3 Dietary Sources and Daily Requirement

The EU reference value for copper is 1 mg per day. Copper-rich foods include:

Chapter 5: Three Minerals in the Big Picture

Zinc, selenium, and copper act at different points in the biological processes that affect skin and hair. Each mineral has its own area of action evaluated by EFSA:

The three authorized claims under Regulation (EU) No. 432/2012 are as follows:

5.1 Practical Dietary Tips

All three trace elements are found in a varied diet. Foods such as oysters, pumpkin seeds, and nuts provide several of these minerals at once. People who follow a plant-based diet should pay attention to bioavailability: soaking, sprouting, and fermentation can increase the absorption of zinc and copper from plant sources.

When using dietary supplements, the recommended daily intake should not be exceeded. Dietary supplements are not a substitute for a varied diet. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Chapter 6: Frequently Asked Questions

What does “normal” skin or “normal” hair mean in the EU sense?

The term “normal” in the EFSA claims refers to physiologically proper function with an adequate supply of the respective mineral. It does not describe a cosmetic improvement or therapeutic effect, but rather the maintenance of the natural state.

Can all three minerals be obtained from food at the same time?

Yes, many foods contain several of these trace elements. Oysters, for example, are rich in zinc and copper, while Brazil nuts provide both selenium and zinc in significant amounts. At the usual dietary amounts, the three minerals generally do not affect one another adversely.

Do the claims apply to all age groups?

The authorized health claims under Regulation (EU) No. 432/2012 refer to the general adult population. Different recommendations may apply to children, pregnant and breastfeeding women, and people with certain medical conditions. Individual advice from a healthcare professional is recommended.

How can you determine your own nutrient status?

Blood tests at your doctor's office can provide information about your zinc, selenium, and copper status. For selenium, the selenoprotein P level is considered a more meaningful marker than the serum selenium level alone. For copper, ceruloplasmin in the blood is frequently measured.