ZINC IS ESSENTIAL FOR HAIR HEALTH

Zinc is the second most abundant trace metal in humans after iron and is required for the function of over 300 enzymes.  Found in almost every human cell and tissue, zinc is vital to several biological functions, including hormone production, cellular growth and digestion.  Zinc, like other biomarkers including hormones, free radicals, antioxidants and macro-or micronutrients can be measured with blood tests.

Zinc is tightly regulated in the body and concentration in the blood changes only slightly in cases of low zinc in the body.

The skin and hair are primarily affected by zinc deficiency or sub-optimal zinc levels in the body.  Zinc supplementation has been shown to support recovery from the most common causes of hair loss: telogen effluvium, alopecia areata and androgenic alopecia.

ZINC REGULATION IN THE BODY

Low levels of zinc in the body can be corrected by decreased loss of zinc in the faeces and urine.  If this is not enough to balance reduced zinc levels, changes to certain metabolic pathways can reduce physiological need of zinc, or zinc can be released by the breakdown of lean muscle mass.

The triage theory predicts that essential proteins can resist low zinc levels for a longer period than non-essential proteins. The proteins that will not be protected are those required for sexual reproduction or any type of growth (including hair growth).  The prioritised protection of some proteins in comparison with others, could explain the ability of the body to maintain blood zinc levels when zinc availability is low.

ZINC REQUIREMENTS, ABSORPTION AND DEPRIVATION

Zinc requirements are calculated to be 3.1 mg per day for men and 2.6 mg per day for women over 16 and under 60 years of age.  This requires an approximate intake of 11 mg for men and 7 mg for women from the diet per day based on an absorption model that puts average zinc bioavailability at 30% as determined by the World Health Organisation.

Zinc absorption is influenced by phytate intake, this should be considered when evaluating zinc intake.  Phytates are found in grains, legumes, nuts and seeds.  Zinc deprivation equates to a sub-optimal intake of 3-5 grams per day.  At around 50% lower than the recommended daily intake, there will be a subtle drop of zinc in the blood.

According to the World Health Organisation, phytates can lower zinc absorption to as little as 15%, a high phytate diet is a risk factor for zinc deficiency.  Other risk factors for low zinc include the consumption of alcohol, smoking, high fat diets and excessive exercise.  In clinical practice, low zinc is contributing to malnutrition, malabsorption, and chronic inflammation.

Nutrient-poor food such as cereals and other processed foods that are consumed on a regular basis in the UK is an accepted contributor to micronutrient deficiency within the population.  Dietary zinc restriction at 30% results in a decrease in blood zinc levels, at 40% the decrease will be clinically evident in the hair and nails, at 50% liver cells will have a reduced zinc concentration.  This preferential zinc distribution in low zinc conditions, explains the resistance to hair follicles in the early stages of zinc deprivation.

ZINC DEPENDENT KERATIN CELL GROWTH

Keratin cells continue through the cell growth cycle if it remains anchored to the scalp.  Zinc is essential for cell cycle progression through normal growth checkpoints.  The concentration of zinc in the cell will determine the progression of the cell from one stage to the next.

Mild zinc deficiency in the cell stalls cell cycle progression and leads to ‘sleeping’ cells with defective and damaged DNA that is reversed when zinc is resupplied.  ‘Sleeping’ cells will not grow even when anchored to the scalp.  A larger number of ‘sleeping cells’ in the growing hair fibre will appear as thinner hair strands that have a shorter growth phase and go into resting phase earlier.

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.

ZINC AND TELOGEN EFFLUVIUM

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.

Telogen effluvium is characterised by a decrease of the anagen to telogen ratio in the hair growth cycle due the reduction of keratin production in the hair matrix. At any time, 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 there are fewer hairs in anagen stage, there will be an increased in hair shedding.  At first this may be a few more hairs in the plughole or left on your pillowcase.  More severe cases can involve more extreme hair loss, sometimes handfuls of hair can be lost at a time.

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 (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 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.

ZINC AND ALOPECIA AREATA

Alopecia areata is characterised by round or oval patches of hair loss on the scalp area.  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.

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.

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.

INCREASING ZINC AVAILABILITY

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.

THE FINAL WORD

Zinc is essential for a robust immune system, DNA synthesis, cell differentiation, protein-protein interactions and steroidogenic action.  Zinc reduces hair loss by reducing the production of DHT, increasing protein synthesis and balancing the immune response by modulating T-cell populations.  Zinc supplementation is a reliable way to resolve the most common types of hair loss in men and women.

REFERENCES

  1. Impairment of cystine-35S incorporation into skin protein by zinc-deficient rats. The Journal of nutrition, 101 (4), pp.445-452.
  2. Oral zinc therapy for zinc deficiency‐related telogen effluvium. Dermatologic therapy, 25 (2), pp.210-213.
  3. 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. 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. Cutaneous androgen metabolism: basic research and clinical perspectives. Journal of investigative dermatology, 119(5), pp.992-1007.