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General Health - Skin - A student guide

By Holly Taylor BSc(Hons) DipCNM MBANT NTCC

The skin is the largest organ in the body – it measures about two square metres and makes up approximately seven per cent of the body’s weight. Its primary roles are sensation and protection; providing us with information about our environment and acting as a barrier against microbes, chemicals, trauma, light and dehydration. However, it also plays an important role in temperature regulation, vitamin D synthesis, absorption and excretion.

The epidermis

The epidermis is the outer layer of skin. It is composed of four or five layers, depending on the skin thickness and, unlike the underlying dermis, it has no blood vessels or nerves of its own. Instead, the epidermis relies on the interstitial fluid to supply oxygen and nutrients and remove waste. This means that good lymphatic flow is vital to ensure long-term skin health.

The epidermis itself is composed of four kinds of cells:

  • Keratinocytes make up 90% of the epidermal cells. They produce the protein keratin, which helps to waterproof the skin cells. New epidermal cells are produced at the bottom of the epidermis and get gradually pushed up towards the surface. During this time, the cells accumulate keratin, flatten and eventually die. By the time they reach the surface, they are no longer living and become easily sloughed off. In healthy skin, this process should take two to four weeks.
  • Melanocytes, within the epidermis, produce the pigment melanin, which gives skin its colour and provides UV protection. Melanin granules collect inside the keratinocytes and cluster to form a layer over their nuclei, protecting the DNA. The amount and distribution of melanocytes is genetic and determines the skin colouration. A high number of melanocytes result in dark, easily tanned skin, whereas an uneven distribution results in freckles.
  • Langerhans cells are specialised immune cells that reside within the epidermis and provide a first-line defence against foreign invaders that enter via the skin. Their primary role is antigen presentation, engulfing pathogens and presenting them to naïve T-cells to illicit an immune response. Langerhans cells are easily damaged by UV radiation.
  • Merkel cells are located in the deepest layer of the epidermis. They are attached to sensory nerve endings and play a role in sensation.

The dermis

The dermis is a layer of connective tissue, lying directly below the epidermis. It is home to a huge network of capillaries, nerves, lymph vessels, glands, hairs and fibres:

  • Collagen fibres within the dermis bind water and help to give skin its tensile strength.
  • Elastic fibres provide the extensibility and elasticity.
  • Hairs are situated in follicles within the dermis, with each follicle connected to touch-sensitive nerve endings. The follicles are also attached to arrector pili muscles, which contract in response to low temperature or emotional stress, causing the hairs to stand on end. Like skin colour, hair colour is determined by your genetic distribution of melanin.
  • Sebaceous glands are connected to the hair follicles and produce sebum, an antimicrobial substance that helps to condition the hair and skin.
  • Sweat glands in the dermis release sweat into hair follicles or onto the skin surface through pores. This is important for temperature regulation and excretion. Sweat itself doesn’t smell, but bacteria on the skin surface can metabolise it into compounds that have a musky odour!
  • Specialised nerve endings within the dermis provide information about light pressure, deep pressure, pain and temperature.

Skin ageing

Most age-related skin changes occur in the dermis. The collagen fibres decrease in number, break apart and become disorganised and the elastic fibres thicken into clumps and fray, losing their elasticity. In addition, the dermis and subcutaneous fat begin to thin, causing the skin to take on the furrowed appearance we call wrinkles. The sebaceous glands also decrease in size so skin becomes dry, broken and more prone to infection and the number of Langerhans cells starts to dwindle, reducing skin immunity.

As we age, blood vessels tend to become thicker and less pliable. In the dermis, this impairs nutrient delivery and results in a slowing of skin cell migration and reduced healing ability. Within the epidermis, decreased functioning of melanocytes can result in unusual skin pigmentation, such as age spots and greying of the hair, as air bubbles replace the melanin.

Factors influencing skin health

With an increasing focus on anti-ageing and the rising incidence of chronic skin conditions, skin health is becoming a hot topic for CAM practitioners. But, with everything from early life experiences through to diet having a potential influence, it’s often difficult to know where to start!

Nevertheless, many age- and disease-related changes in the skin can be accelerated by nutrient deficiencies or free-radical exposure. By understanding the roles of different nutrients in skin health and working to optimise antioxidant defence mechanisms, it’s possible to make positive changes for your clients, while you investigate any other underlying imbalances.

Nutrients and the skin

Vitamin D

The skin has a unique relationship with vitamin D. Not only is it the site of vitamin D synthesis, it is also a target tissue for biologically-active vitamin D metabolites. It has been known for a while now that vitamin D regulates the growth and differentiation of keratinocytes, hence the use of vitamin D analogues as a conventional treatment for hyper-proliferative skin disease psoriasis. However, more recently, researchers have discovered that the cells that produce sebum are also vitamin D responsive, sparking new interest in its role as a possible treatment for acne(1).

From a free radical protection point of view, vitamin D helps protect human keratinocytes against the photo-damage caused by UVB(2)-activated protein kinases(3), which mediate inflammation and apoptosis as part of the cellular response to oxidative damage.

Vitamin D is also able to influence the maturation, differentiation and migration of antigen-presenting cells such as Langerhans cells(4), and induce increases in the secretion of antimicrobial proteins, such as cathelicidin, by keratinocytes and immune cells(5). Moreover, vitamin D is known to help modulate the immune system by regulating T-cell activation and cytokine production, as well as supporting the action of the T-regulatory cell subset. 

These are important considerations when working with atopic eczema, where immune responses are imbalanced and antimicrobial peptide production is compromised. In one trial, oral vitamin D3 supplementation (4000iu) for three weeks was shown to significantly increase the expression of the antimicrobial protein in atopic eczema sufferers, suggesting that vitamin D might be an effective therapy to improve innate immunity in atopic conditions(6).

Vitamin A

Vitamin A plays an important role in the regulation of keratinisation and skin cell shedding, ensuring a smooth skin surface texture. In addition, the metabolites of vitamin A are able to down-regulate sebum production, by suppressing sebaceous gland activity, helping to reduce oiliness. This is the basis for the use of high dose vitamin A (Roaccutane) for acne vulgaris – a skin disease that is characterised by hyperkeratinisation and over-production of sebum(7).

Vitamin A’s benefits also extend to UV protection. Retinoic acid is able to block the UV induction of a family of enzymes that are responsible for the breakdown of collagen within the dermis. It also stimulates keratinocyte and fibroblast proliferation and is able to inhibit UV-induced skin pigmentation. This results in increased collagen production, which helps to thicken and plump the dermis, making it more resistant to trauma(8).

Vitamin E

Vitamin E is the predominant barrier antioxidant in human skin. It helps to protect skin cells against oxidative damage, where it works in combination with vitamin C. It has also been shown to slow melanoma growth, by promoting tumour cell apoptosis and inhibiting angiogenesis. As well as working within the skin, vitamin E is delivered to the skin surface via the action of sebaceous glands, where it has an additional photo-protective role(9). Since sebaceous gland activity decreases with age, older skin may benefit from topical applications containing vitamin E, to boost free radical defences.

Vitamin C

Vitamin C plays an important role in regulating collagen gene transcription, as well as being an important cofactor for three enzymes that participate in the hydroxylation of proline and lysine in collagen biosynthesis. Vitamin C concentration in the skin ranges from 0.4 to 1mg/100g. Upon exposure to a variety of stressors, including UV light, vitamin C concentration in skin decreases. Interestingly, oral supplementation with vitamin C plus vitamin E has been shown to help reduce negative effects, such as erythema, induced by UV stress(10).

Niacin

Niacin is important for the endogenous production of NAD+, a coenzyme vital for hundreds of enzymatic reactions. Cell culture studies have shown that, in states of niacin-deficiency, keratinocytes are more sensitive to photo-damage, as a number of the enzymes that repair DNA and regulate ageing, transcription, apoptosis and stress resistance are unable to function without NAD+. This leads to unrepaired DNA upon photo-damage and a subsequent increase in cell death. This is supported by animal studies, in which genomic instability and increased rates of skin cancer are seen in niacin deficiency models(11).

Pantothenic acid

Pantothenic acid is needed to make co-enzyme A, which is a cofactor in fatty acid oxidation and synthesis. As part of acetyl-CoA, co-enzyme A is a basic building block for sex and adrenal hormones. According to Leung et al; factors that stress the body, or divert pantothenic acid down the sex hormone synthesis pathways, can result in a disordered fatty acid metabolism that drives the seborrhoea and hyperkeratinisation present in acne vulgaris.

Putting this theory to the test, Leung gave 100 Chinese acne sufferers 10g of pantothenic acid a day, in four divided doses, and applied a pantothenic-rich skin cream four to six times a day. After two to six months, the acne sufferers’ symptoms had significantly improved and their skin condition could be maintained with a 1-5g dose of pantothenic acid per day(12).

Data from laboratory studies also suggest that pantothenic acid plays an important role in skin healing processes. During in vitro tests, adding calcium-D-pantothenate to cultured human skin cells, given an artificial wound, increased the number of migrating skin cells and their speed of migration. These effects have been verified in animal tests, where administration of oral pantothenic acid and application of pantothenol ointment to the skin have been shown to accelerate the closure of skin wounds and increase the strength of scar tissue(13). 

Zinc

The skin contains about 20% of the body’s zinc load, with the majority being concentrated in the epidermis. Mechanistic details of the role of zinc in the skin are still being investigated; however, we do know zinc has potent antioxidant actions that help to protect against UV radiation and inflammation and have been linked to decreased risk of various cancers(14).

Zinc has also been shown to enhance wound healing. It serves as a cofactor in numerous transcription factors and enzyme systems that augment the elimination of necrotic tissue by white blood cells and promote keratinocyte migration during wound repair. Zinc is also a key cofactor for many of the collagenase enzymes that control collagen synthesis and modelling during wound repair(15).

Zinc deficiency has been shown to exacerbate certain aspects of immune dysfunction, such as the Th2-dominant allergy profile and compromised skin barrier function. In a mouse model of eczema, a zinc-deficient diet exacerbates skin eruptions and results in increased serum IgE levels. In addition, the T-regulatory cells of the deficient mice also maintain a suppressive function compared to controls(16).

Moreover, zinc levels have been shown to be lower in acne sufferers than healthy controls(17) and a number of trials have shown high-dose zinc to be useful in both acne vulgaris(18) and rosacea(19). Potential mechanisms of action include: antioxidant, anti-inflammatory, antimicrobial and suppression of vasodilation and vascular permeability. 

Copper

When working with zinc long-term, it is also important to provide a suitably balanced amount of copper, to avoid upsetting the delicate ratio between these two minerals, since both are vital for skin function. Copper is an important component of several metalloenzymes, which play a role in skin health. The enzymes that carry out the conversion of

L-tyrosine to melanin, the formation of keratin from prekeratin, the conversion of carotene to retinal and the cross-linking in collagen and elastin tissues, via the enzyme lysyl oxidase, all rely on a copper as a cofactor(20).

Sulphur

Sulphur is needed to make 3_-phosphoadenosine-5_-phosphosulphate (PAPS), which is used in the biosynthesis of many essential body compounds, including dermatan sulfate – a glycosaminoglycan found mostly in skin(21). Consequently, sulphur has a long history of use for a variety of dermatological disorders, such as acne and dandruff, as well as supporting wound healing via keratin production. It has a history of folk usage as a remedy for skin rashes and sulphur-containing baths have a long history of use for the treatment of psoriasis(22).

The most readily available form of sulphur is MSM, which can be used internally as a supplement or applied topically in skin creams. In a recent study by Berardesca et al; an MSM-based cream containing milk thistle was shown to be effective at reducing skin redness, papules and itching in acne rosacea sufferers(23).

Silicon

Silicon contributes to prolyl-hydrolase enzyme activity, which is important for collagen formation(24). It is also present in various glycosaminoglycans, including hyaluronic acid, which helps bind water in the skin, and keratin sulphate, an important component of skin, hair and nails(25). Silicon can be supplied in its inorganic form or as the silicon-rich herb horsetail.

Antioxidants

As a consequence of modern life, skin is constantly exposed to high levels of oxidative stress, which can accelerate signs of ageing and exacerbate certain skin diseases. The main culprits are reactive oxygen species (ROS), which are generated from both internal and external sources.

In psoriasis, oxidative stress can influence certain cellular pathways involved in inflammation and gene expression. The activation of these pathways results in the release of growth factors and cytokines, which causes an over-proliferation of skin cells(26).

ROS levels have also been found to be higher in rosacea sufferers than healthy controls. In rosacea, ROS, often triggered by exposure to UV light, induce inflammatory mediators that stimulate fibroblasts and alter collagen turnover in the dermis. The damaged dermal matrix then permits accumulation and prolonged retention of inflammatory mediators(27).

Disordered oxidative balance has also been demonstrated in acne vulgaris patients. In these cases, ROS are produced by white blood cells in response to colonisation of the skin follicles by the P. acnes bacterium. Squalene, a lipid in sebum, normally helps to protect the skin from lipid peroxidation, but, in the face of excessive ROS generation, it also becomes oxidised. The oxidised squalene then stimulates hyper-proliferative behaviour of keratinocytes and actually promotes acne lesion formation(28).

Since free radical processes play such a central role in both skin ageing and many skin diseases, it stands to reason that antioxidants could provide a useful therapeutic option. This is demonstrated in a recent double-blind, placebo-controlled trial, where psoriasis patients receiving antioxidant supplements containing 50mg CoQ10, 50mg _-tocopherol and 48mcg selenium per day for 30-35 days showed significant improvement in their symptoms and markers of oxidative stress, compared to a control group(29). In other studies, astaxanthin, a powerful carotenoid antioxidant, has been shown to quench free radicals and help protect the collagen fibres from damage(30), increase the moisture and elasticity in the skin(31), as well as reducing sebum production and skin inflammation(32).

Essential fatty acids

Essential fatty acids are found in the membrane of every single cell in the body, including skin cells, where they help to maintain membrane fluidity. When consumed in the correct ratio, essential fatty acids are also strongly anti-inflammatory, an outcome that is particularly relevant when dealing with skin conditions such as acne and eczema.

Epidemiological studies show that communities that maintain a diet high in omega 3 fatty acids have low rates of acne(33). In addition, recent research has shown that inhibition of the inflammatory mediator leukotriene B4 reduces sebum production and improves acne symptoms(34). This is particularly relevant since fish oil is well documented to have leukotriene B4-inhibiting(35) and androgen-lowering(36) properties in humans.

The increasing prevalence of atopic eczema has been linked to an excess consumption of omega 6, which favours the formation of the inflammatory eicosanoid PGE2 and promotes the Th2 subset(37). In clinical trials, both DHA(38) and hemp seed oil(39) have been shown to improve eczema symptoms and perinatal supplementation with fish oil has been shown to lower atopic eczema rates among infants with a family history of allergies(40).

So, while it is important to appreciate that nutrients, antioxidants and essential fats are not the be-all and end-all, a good skin support formula, an antioxidant complex and the correct balance of essential fats can provide an excellent basis for a skin health protocol. This approach not only provides prompt symptom improvements, it also allows you to gain the client’s confidence so you have extra time to address their more complex imbalances.


Article References

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