ZINC; ESSENTIAL FOR HAIR HEALTH

Zinc is required for the function of over 300 enzymes and is the second most abundant trace metal in humans after iron.  Found in almost every human cell and tissue, zinc is vital to several biological functions, including hormone production, cellular growth and digestion.

Zinc raises testosterone levels in the body which increases hair growth. Zinc is essential for the protein synthesis and cell changes needed for an epidermal cell to develop into a mature keratin cell within the hair matrix.  Zinc also balances immune response by modulating the behaviour of the immune system.

Zinc supplementation has been shown to support recovery from telogen effluvium, alopecia areata and androgenic alopecia.

ZINC AND TELOGEN EFFLUVIUM

Telogen effluvium is characterised by a decrease of the anagen to telogen ratio due the reduction of keratin production in the hair matrix. More than 90% of all hairs should be in growing phase (anagen) and around 10% will be resting or in preparation to shed (telogen).  When the percentage of hairs in telogen phase reaches around 30-40% there will be a greatly reduced number of hairs on the scalp, this is often a cosmetic concern for a hair loss patient.

When there are fewer hairs in anagen stage there will be an increased in shedding.  At first this may be a few more hairs in the plughole or left on your pillow case.  More severe cases can involve more extreme hair loss, sometimes handfuls.  Once the anagen to telogen ratio gets to around 70% anagen and 30% telogen, there will be a noticeable decrease in hair thickness.  As the percentage of hair in anagen gets lower, hair will appear to grow slower and appear fine and lacklustre.  Hence the saying ‘it’s fine, but there’s a lot of it’.

In telogen effluvium cases, the fallen hair features a bulb of keratin at the root that signifies hair has gone through a compete and typical cycle in a reduced period of time (Park et al, 2020).  This keratin bulb is formed in catagen phase when the hair fibre detaches from the blood supply keeping the hair embedded in the scalp until it sheds.  If the keratin bulb is not sufficiently formed enough to provide a stable anchor, there will be further shedding as the hair fibres begin to detach prematurely.Zinc controls and regulates keratin proliferation and differentiation, in moderate doses zinc significantly inhibits hair follicle regression into catagen phase.

Zinc controls expression of keratin polypeptides due to its influence on keratinolytic enzyme activity.  Hsu and Anthony [1] demonstrated zinc was necessary for the incorporation of sulphur into L-cysteine and then into the proteins in the skin and hair matrix.  Cysteine is a key component of all keratin proteins due to its ability to form the disulphide bridges that make up the rigid and fibrous hair matrix.

Whilst most cases of telogen effluvium are acute and self-resolving, chronic telogen effluvium can last over a period of years.  Karashima et al [2] treated 4 telogen effluvium patients with 75mg zinc and found hair loss resolved or improved.

Hair cycle; growth and regression of the hair follicle

ZINC AND ALOPECIA AREATA

Alopecia areata is characterised by round or oval patches of hair loss on the scalp area.  This is classed as an autoimmune condition with a complex genetic influence.  There several associated diseases and complex genetic influence.  There several associated diseases and conditions such as allergies and asthma.  The hair follicle suffers no permanent injury and hair will often spontaneously regrow after a period.

Alopecia areata is histologically characterised by an infiltration of T cells in the dermal papilla after immune activation.  Complications arise when the T cell population is imbalanced.  Zinc supplementation decreases the activity of proinflammatory cells that cause destruction to the hair follicle.  Clinical features include round or oval patches of hair loss on the scalp area. This is an autoimmune condition with a complex genetic influence. There are several associated diseases and conditions such as allergies and asthma.  The hair follicle suffers no permanent injury and hair will often spontaneously regrow after a period.

A case study by Park et al, demonstrated the therapeutic effect and changed serum zinc concentration after zinc supplementation in patients with alopecia areata who had low zinc levels but were not zinc deficient [3].  After supplementation with 50 mg zinc gluconate per day for twelve weeks, the positive response group had a mean serum zinc concentration increase of 40.9 µg/dL compared to the negative response group with a mean serum zinc concentration increase of 7.7 µg/dL.  In the positive response group, the lowest level of serum zinc was 71 µg/dL.

ZINC AND ANDROGENIC ALOPECIA

Androgenic alopecia is type of hair loss that affects the front and top pf scalp.  Male pattern hair loss generally presents as a receding hairline and / or loss of hair on the scalp.  Female pattern hair loss generally appears as a widening of the parting, a recession at the temples or diffuse hair loss.

Androgen dependant hair loss such as androgenic alopecia develops after altered androgen metabolism results in an increase of dihydrotestosterone (DHT) and a decrease of testosterone in the hair follicle.  DHT reduces hair growth by enhancing expression and translation of genes that encourage premature entry into catagen phase [4].

Zinc is important for the function of hydroxysteroid dehydrogenases that convert adrostenediol, dehydroepiandrosterone and androstenedione to testosterone.  These hydroxysteroid dehydrogenases also inactivate DHT into adrostenediol lowering the concentration of local DHT [5].

Zinc also increases local levels of testosterone allowing binding of growth factor to sustain normal hair growth.

Testosterone and the hair growth cycle

THE FINAL WORD

There are several ways to increase the level of zinc in your diet, if you suspect that your hair is thinning and/or shedding abnormally:

  1. Eat more foods containing zinc: Oysters contain the most zinc per serving than any other food at 74 mg per serving or 493% of the RDA. Red meat such as beef contains the second highest amount of zinc at 7 mg per serving, and poultry contains 2.4 mg per serving.  Beans, nuts and dairy products all include zinc. If you are vegan or vegetarian, you may require as much as 50% more of the RDA for zinc than meat-eaters.
  2. Reduce processed foods:  Processed food contains lower levels of zinc and other essential nutrients for hair health.  Avoid food, such as flavoured yoghurts, with added modified maize starch.
  3. Lower your alcohol intake: Alcohol induces changes in zinc metabolism that can lead to zinc deficiency.
  4. Begin zinc or hair loss supplementation: Zinc can also be found in numerous forms of zinc dietary supplements such as zinc gluconate, zinc sulphate, and zinc acetate.
  5. Limit starchy foods to one portion a day:  High phytate food like bread, potatoes and rice can inhibit absorption of zinc.

Zinc is essential for a robust immune system, DNA synthesis, cell differentiation, protein-protein interactions and steroidogenic action.

REFERENCES

  1. Hsu J and Anthony W, 1971. Impairment of cystine-35S incorporation into skin protein by zinc-deficient rats. The Journal of nutrition, 101 (4), pp.445-452.
  2.  Karashima et al 2012. Oral zinc therapy for zinc deficiency‐related telogen effluvium. Dermatologic therapy, 25 (2), pp.210-213.
  3. Park et al. The therapeutic effect and the changed serum zinc level after zinc supplementation in alopecia areata patients who had a low serum zinc level. Annals of dermatology. 2009 May 1;21(2):142-6.
  4. Chen et al, 2020. Dihydrotestosterone regulates hair growth through the Wnt/β-catenin pathway in C57BL/6 mice and in vitro organ culture. Frontiers in pharmacology, 10, p.1528.
  5. Chen et al, 2002. Cutaneous androgen metabolism: basic research and clinical perspectives. Journal of investigative dermatology, 119(5), pp.992-1007.

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