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‘The skin as a mirror of health’...

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01 September 2016, at 1:00am

Lee Danks in the 8th in his series for Royal Canin asks: what role does diet truly play in skin vitality?

“HIS COAT LOOKS GREAT – WHAT’S HE BEING FED?” It’s a sound bite often heard when a glossy coat or a dander-free dog is greeted in the park, and for good reason: there are many links between skin and coat health and nutrition. This article aims to lend merit to a few quotes which you may use in a consultation room scenario when advising on an itchy dog or scratching cat. 

‘The skin is a multi-functional organ’ 

As the largest organ in the body – composing 12% of the body-weight of the adult dog – the integument arguably fulfils more functions than any other. At face value it’s responsible for a pet’s appearance: changes to colour serve as a physiological indicator in the case of flushing red with vasodilation through to the jaundice, pallor or pettichiae as a marker of pathology.

A good coat is often a thing of beauty and in addition, the way in which hair is held by arrector pili muscles at the follicle can communicate much to us, particularly in times of stress.

The long primary hair is accompanied by up to 10 to 15 finer, shorter secondary hairs in the cat whereas the dog usually has only three to five.

Coat colour, density and growth rate are largely genetically determined and this in turn can influence a pet’s dietary requirements. 

‘The skin and coat are responsible for 30% of the dog’s daily protein requirements’

When a diet is protein-deficient or fails to deliver a sufficient supply of essential amino acids, signs are most often seen at the level of the skin. Let’s remember also that this depends not only on the protein composition and source (albeit plant or animal), but also its digestibility. Nutritionally balanced pet foods should focus on this feature, particularly when formulated for dermatological cases.

‘Think bricks and mortar’

This analogy has been with us since the 1970s and still rings true today. Dermatologists may argue that the primary role of the skin is as an environmental barrier. This complex barrier needs to be responsive and flexible to movement, incorporate sensory and thermo-receptors but most importantly needs to deal with the desiccating, irritant, sometimes toxic outside world. It is the pet’s “first line of defence”.

The epidermis has a stratified structure. From the cornified and constantly-shedding outer stratum corneum to the basal cell layer of keratinocytes, there are sequential stages which result in flattened protein-rich cells, called corneocytes which give the outer skin its structure. These corneocytes are surrounded by a specialised lipid matrix: the mortar between the bricks.

The most likely way an agent can penetrate through the epidermis is by traversing a tortuous pathway around the cells. The intracellular lipids, primarily consisting of fatty acids, sterols and ceramides moderate this ingress while at the same time have a role in moderating skin hydration and cell differentiation.

‘Thick skin is a gift’

Overall, canine skin is thinner than human skin despite the fact that it has a greater number of cell layers. In addition, individual dogs prone to atopic (CAD) or flea allergy dermatitis are reported to have poor barrier function, much the same as people with psoriasis, icthyosis, eczema/ atopic dermatitis, essential fatty acid deficiencies and winder-induced xerosis.

For this reason, many patient management solutions focus on correcting the “leaky” skin structure which favours antigen penetration or secondary complications. From a dietary standpoint, it has been demonstrated that one particular cocktail of four B-vitamins and one amino acid bene t the skin in vivo following nine weeks of feeding, demonstrated by reductions in trans- epidermal water loss (TEWL).

‘Essential means essential’

Fatty acids have long been used to help manage dermatoses in cats and dogs, with a particular focus on omega-3 and omega-6 polyunsaturated fatty acids (PUFAs).

Those which are essential, either as precursors or end-point eicosapentanoic and docosahexanoic acids (EPA/DHA), can’t be synthesised de novo in the cat or dog, and therefore are required in the diet.

Beyond providing the essentials, PUFAs are often supplemented in skin diets. The omega-6 series is most frequently associated with the physical characteristics of healthy skin and coat, whereas omega-3s are more often linked to cellular activity and cell membrane composition and fluidity, therefore function.8

Disorders of fatty acid metabolism, namely enzyme deficiencies, are also considered a predisposing or aggravating factor for canine atopic dermatitis3, further supporting their use in this population.

‘Adverse food reactions are the lucky ones’ 

As obscene as it may sound, when general practitioners and dermatologists find it difficult to distinguish between food and environmental allergies, a dietary link to aetiology is relatively easy to manage.

Diet may indeed trigger food- induced CAD, as described within the summation theory from the American College of Veterinary Dermatology (ACVD) appointed Task Force on Canine Atopic Dermatitis.

Where this is so, placing a patient on a strict elimination diet trial is invariably easier (with both a diagnostic and long-term management view) than positively identifying an environmental allergen, executing complete avoidance, de-sensitisation or immunosuppression.

One can see that over the course of these few phrases, some of the numerous links between diet and skin can be made plain.

With this recognition we can engage clients who present us with a dermatological dilemma, and choose poignant take-home sound bites to reform the way they feed their pet, for better long-term health. It’s easily-recalled behaviour-changing messages such as these which can really make the difference.

References and further reading

  1. Dethioux, F. (2008) Nutrition, skin health and coat quality. Veterinary Focus 18 (1): 40-46.
  2. Elias, P. and Friend, D. (1975) The permeability barrier in mammalian epidermis. Journal of Cell Biology 65: 180-191.
  3. Furhmann, H., Zimmermann, A., Guck, T. and Oechtering, G. (2006) Erythrocyte and plasma fatty acid patterns in dogs with atopic dermatitis and healthy dogs in the same household. Canadian Journal of Veterinary Research 70: 191-196.
  4. Hill, P. and Olivry, T. (2001) The ACVD taskforce on atopic dermatitis (V): biology and role of in ammatory cells in cutaneous allergic reactions. Veterinary Immunology and Immunopathology 81: 187-198.
  5. Marsella, R. and Sousa, C. (2001) The ACVD taskforce on atopic dermatitis (XIII): threshold phenomenon and summation of effects. Veterinary Immunology and Immunopathology 81: 251-253.
  6. Mundt, H. and Stafforst, C. (1987) Production and Composition of dog hair. Edney, A. (ed.) Nutrition, Malnutrition and Dietetics in the Dog and Cat. British Veterinary Association: 62-65.
  7. Pibot, P. (2008) Feline and canine coats: breed variations in texture and length. Veterinary Focus 18 (1): 2-3.
  8. Schumann, J., Basiouni, S., Guck, T. and Fuhrmann, H. (2014) Treating canine atopic dermatitis with unsaturated fatty acids: the role of mast cells and potential mechanisms of action. Journal of Animal Physiology and Animal Nutrition 98: 1,013- 1,020.
  9. Watson, A., Fray, T., Bailey, J., Baker, C., Beyar, S. and Markwell, P. (2006) Dietary constituents are able to play a bene cial role in canine epidermal barrier function. Experimental Dermatology 15: 74-81.