Oat Oil Improves the Skin Barrier - The Dermatologist

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Oat Oil Improves the Skin BarrierOat oil is rich in linoleic acid, which is an essential polyunsaturated fatty acid critical for the maintenance of the skin permeability barrier.Michael Southall, PhD, Apostolos Pappas, PhD, Glenn Nystrand, BS, Judith Nebus, MBAJohnson & Johnson Consumer Companies, Inc.The outermost layer of the epidermis, the stratumcorneum, functions as a two-way physical andchemical barrier: it prevents both the penetration ofnoxious agents from the environment into the skin andthe evaporation of water in the opposite direction. Thestratum corneum is formed by corneocytes and intercellularlipids (lamellae), which contain mostly ceramides(50% of the stratum corneum lipid mass), cholesterol(25%) and free fatty acids (10%). 1,2 The specific mixtureand organization of these lipids in the space betweencorneocytes allows the proper maintenance of the permeabilitybarrier. The significance of ceramides for thestratum corneum barrier has been extensively reportedand the essential fatty acid (EFA) linoleic acid (LA), containedin ester linkage in acylceramides (ceramide fractions),seems particularly important for the normal barrierfunction. 2An alteration in stratum corneum lipids has beenidentified in several skin disorders with damaged permeabilitybarrier, including atopic dermatitis (AD). Acompromised barrier increases the penetration of irritants,allergens and pathogens, thus causing or furtheringskin inflammation. 3,4 A defective barrier is not only akey feature of AD, but the degree of skin barrier damagecorrelates with the disease severity. 5 For this reason,emollients that repair and protect the stratum corneumare important for the general skin health as well as for theimprovement of certain eczematous conditions. 4Linoleic Acid and Skin BarrierLA is one of the most significant lipids for the maintenanceof barrier function. 6 In fact, recent studies suggestthat LA is essential for the formation of the lamellarphase of the stratum corneum lipids. 2,7 Additionally,studies showed that stratum corneum free fatty acids,including LA, are important for the maintenance of thesurface “acid mantle,” which, in turn, seems importantfor both the integrity of the permeability barrier andstratum corneum cohesion. 8The importance of LA for a healthy skin barrier hasbeen known since the 1930s, when pre-clinical experimentsdemonstrated that a prolonged fat-free diet wouldlead to severe scaly dermatosis and a significant increasein transepidermal water loss (TEWL), and that oral intakeof LA would reverse these symptoms. 9 Humanclinical studies have subsequently confirmed the reversalTable 1. Lipid Class (%) composition in the oat oil oftriple oatLipid Class %Triglycerides 83.4Free Fatty Acids 6.8Diacylglycerols 8.9Phospholipids 0.9Triglycerides are the most abundant lipids in oat oil. The fatty acids oleic acid (OA) and linoleicacid (LA) are contained in various percentages in each of the four lipid classes (35% to 43% forOA and 36% to 45% for LA).of the cutaneous manifestation of EFA deficiency afterconsumption of LA-rich diet. 10 Since then, studies haveshown skin barrier improvement also via topical applicationof LA or of oils rich in LA (eg, sunflower seedoil). 11,12 In 1975, Prottey et al demonstrated decreasedscaliness and decreased TEWL (ie, improved barrier)in EFA deficient patients treated for 2 weeks with sunflower-seedoil applied to the forearms; interestingly,improvement did not occur in the contralateral forearmtreated with olive oil, rich in oleic acid. 11In preclinical studies, topical LA-rich oils were alsoshown to improve the skin barrier in EFA deficiencymodels or in skin disrupted by sodium laurate; in bothgroups, skin applications of sunflower seed oil normalizedthe high TEWL. 12 Interestingly, linoleic acid fromthe sunflower seed oil application was detected in theepidermal lipids of the EFA deficient group. 12 A laterstudy by Elias et al 6 confirmed these results: in an EFAdeficient preclinical model, the application of pure LAto the skin quickly improved the barrier function (decreasedTEWL), while contralateral application of pureoleic acid produced deterioration of the skin barrier(increased TEWL). In fact, pure oleic acid, in its unbound,free fatty acid form, has been shown to actuallyincrease the skin permeability by disrupting the lamellarlipid arrangement in the stratum corneum and thusfunctioning as a penetration enhancer. 13,14 It is importantto note, though, that the vast majority of oleic componentsin vegetable oils are present in esterified and boundforms. Topical formulations, containing vegetable oils,are designed with additional stabilization to maintain thestructure of the emulsion, to normalize the pH rangeand to prevent microbial growth. All of these factors are2 September 2012 • Supplement to The Dermatologist ®
Oat Oil Improves the Skin BarrierTable 2. Fatty acid (%) composition in the oat oil of triple oatPhospholipid Diacylglycerol Free Fatty Acid TriglyceridesPalmitic 16:0 12.9 15.3 16.7 14.7Stearic 18:0 3.2 2.3 1.9 1.6Oleic 18:1 (n-9) 35.0 42.9 38.3 42.7Linoleic 18:2 45.3 36.1 39.2 37.0The majority of fatty acids are esterified in the triglyceride fraction of oat oil.beneficial for maintaining the quality of the vegetable oilin the formulation.The importance of lipid emulsions containing LA inrepairing the barrier function has been highlighted in afew studies. A recent study investigated the barrier repairability of two topical emulsions containing a mixture oflipids, after the skin was damaged by sodium lauryl sulfate(SLS). 15 The emulsion containing LA in combination withceramides III, IIIB, VI, phytosphingosine and cholesterolproduced a significantly faster barrier recovery comparedto the emulsion containing only ceramides III and IIIB.OatOat is a natural agent that contains a variety of activecompounds, including: lipids with a high percentage ofunsaturated fatty acids, starches and hydrocolloid β-Dglucan,avenanthramides and other antioxidants (mostlyphenolic esters), saponins and vitamins. 16,17 The total lipidcontent is relatively high (around 6% to 12% in groats)compared to other cereals; of the groat lipids, about 41%are triglycerides and 5% free fatty acids. 18 Oats are particularlyrich in unsaturated fatty acids, with polyunsaturatedLA (18:2) and monounsaturated oleic acid (18:1)accounting for approximately 40% and 36% (averages) ofthe total groat fatty acid pool, respectively. 18 Other fattyacids include palmitic acid (16:0, about 19%) and minimalamounts of linolenic, stearic and myristic acids. 18 Itshould be noted, though, that the percentages of oat oilfractions reported in the literature vary depending oncultivars, storage and extraction method. 18The chemical polymorphism of oats is at the basis oftheir multiple beneficial effects, including barrier protection,moisturization, anti-inflammatory, soothing, cleansing,etc. For decades, oat-containing emollients have beenused in various eczematous conditions and recent studieshave confirmed their importance in the treatmentof AD 19-21 and xerosis. 22 Oat is currently used in topicalformulations either as colloidal oatmeal or as its separatedfractions. Colloidal oatmeal is derived from the wholedehulled grain and is categorized as an over-the-counter(OTC) skin protectant drug, regulated by the FDA. 23 Additionalrecent investigations have focused on the specificbiological effects of active compounds extracted from oat,such as avenanthramides and oat oil. Avenanthramides arephenolic molecules that have shown potent anti-inflammatoryactivity both in vitro and in vivo. 17 Oat oil hasalso been recently studied for its beneficial dermatologicaleffects and it is likely that its LA fraction plays a major rolein the maintenance of the epidermal water barrier. 24Oat Oil ExperienceIn view of its potential benefits, oat oil has been recentlyincorporated in new topical products. In this article,we review a novel moisturizer formulated with amixture of three active oat compounds (triple oat): colloidaloatmeal, avenanthramides and oat oil. Each oatingredient is carefully sourced to ensure quality andconsistency. The specific oat crop, used in the manufactureof this oat oil, is grown from selected soils in aparticular region of northwestern Europe, virtually freeof the risk of pollution. Additionally, the extracted oatoil is carefully processed to retain its biologically activecompounds and its quality is assured through standardizationof extraction procedures with non-toxic solventsand relatively low temperatures.The oat oil in triple oat contains more than 70% unsaturatedfatty acids. LA, in particular, constitutes approximately37% of the total fatty acid fraction, presentin part as free fatty acid, and in part esterified tovarious lipids (mostly triglycerides) (Tables 1, 2). Thehigh phospholipid content and relatively high unsaturatedfatty acid content found in oat oil are very differentfrom other natural oils. Most extracted natural oils (eg,olive oil) are primarily composed of triglycerides, withno phospholipids, and very few fatty acids.A 2-week study was performed to evaluate the effectivenessof a triple oat lotion (colloidal oatmeal, oat oiland oat extract) on individuals with mild to moderate itchdue to extra dry skin on the lower legs. Twenty-nine patientsapplied the triple oat lotion twice a day for 2 weeks.Clinical evaluations demonstrated significant improvements(p
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