The stratum corneum is the outermost layer of mammalian skin. This layer primarily acts as a barrier to protect us from external environmental stresses and to prevent excessive transcutaneous water loss. The cells of the stratum corneum, corneocytes and the lipids between them, Ceramides, accomplish this important function. Disruptions of this barrier, through either physical trauma caused by dermatitic conditions like eczema or by simple aging, result in this important function being compromised. The result is decreased elasticity, increased susceptibility to infection and increased water loss which can lead to aging conditions such as wrinkles and fine lines, as well as an overall dullness to the skin's texture. 36, 37
Plants contain structures which are nearly 100% chemically identical to human Ceramides. These plant-derived, or phyto-derived, Ceramide products can aid in creating the protective barrier in the epidermis. Supplementation with an oral agent of Ceramide replaces the components lost through aging and has hydration effects. 38
The moisturizing effect comes from the Ceramides being carried directly to the stratum corneum via the blood. This direct method improves the functionality of the Ceramides and produces results not seen in cosmetic topical applications. 39
Ceramides have become an important compound for skin protection. Lipid depletion and replenishment studies have shown that Ceramides play an essential role in establishment and maintenance of the water-retaining properties of skin. Since it is known that Ceramides decrease with age, it has been suggested that increased transepidermal water loss is the result of their reduced presence in the skin. In short, Ceramides play an important role in preventing moisture loss which can be caused by physical trauma or aging. 4o
It is also known that Ceramides inhibit Melanogenis and are thought to promote a pigment lightening effect. Melanogenis is a process by which the skin produces pigments that give our skin its unique tone and color. This is particularly helpful for hyper-pigmentation which causes age spots and other discolorations of the skin. In an in vitro study using B-16 melanoma cells, the melanogenic effect of Ceramides was observed. Ceramides exhibited a stronger whitening effect when compared to ascorbic acid, arbutin, and ellagic acids. 41, 42
The moisturizing effect of Ceramides was established in several clinical studies. These studies show that Ceramides are absorbed via the digestive system and carried to the stratum corneum by blood, where it circulates, and produces a significant effect in promoting a water barrier in the layers of the skin. Therefore, Ceramides in the stratum corneum of the skin play important roles for maintaining a barrier function and protecting the skin from harm. 43
