Vitamin C in the Skin - Simplified

Vitamin C in the Skin – Simplified
Vitamin C in the form of ascorbic acid (aka; L-ascorbic acid) is a potent antioxidant with many rejuvenating benefits for the skin. When vitamin C levels in the skin are sufficient, it repairs and impedes environmental aging, preserving skin's health and youth longer. 

Skin layers - shield
The primary role of the skin is to encompass and shield internal tissues and organs from the external environment. The skin's main structure is composed of two layers, the epidermis, and the dermis.

The epidermis – surface layer
The non-vascular epidermis is composed of many layers of cells migrating towards the surface of the skin. During migration, the cells undergo a complex transformation into a water-resistant barrier that resists dehydration and external invasion of the internal tissues before eventually shedding. A continuous rejuvenating process that protects and replaces skin cells. 

The dermis – tissue layer
The vascular dermis, mainly composed of collagen fibers, fibroblasts, and blood vessels, provides structure, support, and nutrients to the epidermis. It is believed, nutrient delivery does not reach the outermost layers of the epidermis (the stratum corneum); thus, a topical application of nutrients to the skin's nutrient-deficient epidermal layers may be beneficial to maintaining the overall health and youth of the skin. 

Passing through the lipid barrier - skin's brick wall
One role of the lipid barrier is resisting access to external substances. Studies indicate water-soluble vitamin C in the form of ascorbic acid will not pass through the lipid barrier unless formulated at a pH below 4.

Saturation levels - skin's reservoir
"Optimum skin concentrations of the vitamin are not yet known." [source]

A popular pigskin study confirmed, "L-ascorbic acid must be formulated at pH levels less than 3.5 to enter the skin. Maximal concentration for optimal percutaneous absorption was 20%. Tissue levels were saturated after three daily applications; the half-life of tissue disappearance was about 4 days. Derivatives of ascorbic acid including magnesium ascorbyl phosphate, ascorbyl-6-palmitate, and dehydroascorbic acid did not increase skin levels of L-ascorbic acid." [study] 

A simple analogy - skin's fuel
Think of vitamin C as skin's fuel. Topical C levels must be refueled before depletion to maintain optimum antioxidant benefits. 

For best results, refuel the skin's C topical levels every 24 hours.

Self-maintenance - is key
Once vitamin C passes through the lipid barrier, it fuels the skin with a reservoir of antioxidants that it cannot be washed or rubbed off and remains active in the skin for several days after application unless prematurely depleted* by exposure to environmental assaults.

*Skin repeatedly exposed to environmental assaults such as unprotected sun exposure, nicotine, ozone, etc. may benefit from an additional 1-2 pump overlay of any of our nutrient cocktails per application.

Maintain C levels - inside out
It is believed that the epidermis's non-vascular structure and barrier, is the main roadblock to sufficient nutrient delivery; thus supplying vitamin C through both, topical application and dietary (supplements, fruits, and vegetables), ensure all layers of the skin are sufficiently supplied; enabling the skin to function properly, restore itself and remain healthier longer.

Feeding the skin - less is best 
Skin will do what it should naturally with the right nutrient balance (both topically and dietary); start with less until you find the right balance; as skin improves and adjusts, reduce or add topical nutrient supply.  

Sources
Linus Pauling Institute Vitamin C and Skin Health
Nutrients. 2017 Aug; 9(8): 866. The Roles of Vitamin C in Skin Health [PubMed]
Indian Dermatol Online J. 2013 Apr-Jun; 4(2): 143–146. Vitamin C in Skin Health [PubMed]
J Invest Dermatol 2001 Nov;117(5):1212-7. Aging- and photoaging-dependent changes of enzymic and nonenzymic antioxidants in the epidermis and dermis of human skin in vivo. [PubMed]
GItal Dermatol Venereol. 2015 Dec;150The skin barrier function: differences between intrinsic and extrinsic aging. [PubMed]
Clin Dermatol. 2011 Jan-Feb;2Dry skin in the elderly: complexities of a common problem. [PubMed]
Free Radic Biol Med. 2002 Nov 15;33(10):1355-62. UVR-induced oxidative stress in human skin in vivo: effects of oral vitamin C supplementation. [PubMed]
Dermatol Surg. 2001 Feb;27(2):137-42.Topical L-ascorbic acid: percutaneous absorption studies. [PubMed]
J Clin Aesthet Dermatol. 2015 Sep; 8(9): 39–47.The Tricky Tear Trough A Review of Topical Cosmeceuticals for Periorbital Skin Rejuvenation. [PubMed]
Skin Pharmacol Physiol 2004 Jul-Aug;17(4):200-6. Topical activity of ascorbic acid: from in vitro optimization to in vivo efficacy. [PubMed]
J Cutan Aesthet Surg 2016 Jul-Sep; 9(3Neocollagenesis and Neoelastinogenesis: From the Laboratory to the Clinic. [PubMed]
Comput Biol Med. 2016 Aug 1;75:151-9.Assessment of penetration of Ascorbyl Tetraisopalmitate into biological membranes by molecular dynamics. [PubMed]
Skin Res Technol. 2008 Aug;14; In vitro antioxidant activity and in vivo efficacy of topical formulations containing vitamin C and its derivatives studied by non-invasive methods. [PubMed]
Guang Pu Xue Yu Guang Pu Fen Xi. 2012 Dec;32. The study of absorption efficiency and restoring effects of collagen and ascorbic acid on aged skin by fluorescence and reflection spectroscopy. [PubMed]
J Drugs Dermatol. 2012 Jan;11(1):51-6.Split-face study of topical 23.8% L-ascorbic acid serum in treating photo-aged skin. [PubMed]
J Cosmet Dermatol. 2006 Jun;5(2):150-6An immunohistological study of anhydrous topical ascorbic acid compositions on ex vivo human skin. [PubMed]
J Invest Dermatol 2002 Apr;118(4):565-72. Vitamin C regulates keratinocyte viability, epidermal barrier, and basement membrane in vitro, and reduces wound contraction after grafting of cultured skin substitutes. [PubMed]
J Invest Dermatol. 2005;125:826–832. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin. [PubMed]
Clin Cosmet Investig Dermatol 2015; 8: 591–599.Phosphatidylcholine liposomes as carriers to improve topical ascorbic acid treatment of skin disorders. [PubMed]
Int J Pharm 2001 Mar 14;215(1-2):51-6.Comparison of human skin or epidermis models with human and animal skin in in-vitro percutaneous absorption. [PubMed]
Pak J Biol Sci. 2015 Jan;18(1):11-8.Effects of Oral Vitamin C Supplementation on Anxiety in Students: A Double-Blind, Randomized, Placebo-Controlled Trial. [PubMed]
PLoS Med. 2005 Sep; 2(9): e307. Misleading Information on the Properties of Vitamin C [PubMed]
Nutr J. 2003; 2: 7. Vitamin C in human health and disease is still a mystery? An overview [PubMed]
Eur L Clin Nutr. 1990 Jun;44(6):447-60.Effects of age and intake on vitamin C disposition in females. [PubMed]
Nutrients. 2013 Dec; 5(12): 5161–5192. Myths, Artifacts, and Fatal Flaws: Identifying Limitations and Opportunities in Vitamin C Research [PubMed]
Proc Natl Acad Sci U S A. 2001 Aug 14; 98(A new recommended dietary allowance of vitamin C for healthy young women [PubMed]
Am J Clin Nutr. 2007 Oct;86(4):1225-31.Dietary nutrient intakes and skin-aging appearance among middle-aged American women. [PubMed]
J  Am Coll Nutr 2001 Feb;20(1):71-80. Skin wrinkling: Can food make a difference? [PubMed]
Free Radic Biol Med. 2002 Nov 15;33(10):1355-62. UVR-induced oxidative stress in human skin in vivo: effects of oral vitamin C supplementation.[PubMed]