Pro-vitamin D: precursor of sun hormone
Pro-vitamin D is the precursor from which skin produces vitamin D with the influence of sun rays. Vitamin D controls important metabolism functions in the body. It has positive effects on bone synthesis and bone density, production of bone stem cells, immune system, muscles, skin and psyche.
Recently, other effects have been discussed: however, they have not been clearly scientifically proven. For example, it is not sure whether vitamin D protects against severe cases of COVID. It seems to be of no advantage to prevent cancer or cardiovascular diseases.
Vitamin D is essential for health; however, it is no magic potion. Persons who want to take special vitamin products should have measured their vitamin D level by a doctor before.
Dietary supplements or light?
Actually, many Central European people have low vitamin D levels. Besides too short periods outdoors in daylight, old age, metabolic disorders, special drugs or diseases can impair vitamin D synthesis. Even full veil hinders vitamin D production. Humans with intensive skin pigmentation and dark skin color require more UVB rays to build vitamin D whereas they often have higher bone density.
Even though in some countries, certain foods are enriched with vitamin D, the intake via food amounts to only 10 to 20 percent.
We derive vitamin D2 from plant sources, like cashews, mushrooms, preferably dried in sun light. D3 comes from animal sources, like sea fish, eggs, milk. The milk of cows frequently put out to pasture and sun light in the barn contains sufficient vitamin D so that one glass of milk a day is sufficient for the body for self-production.
80 to 90 percent the body produces itself with help of sun light. That is why vitamin D is also called sun hormone.
Vitamin D is the generic term for fat-soluble vitamin forms, so-called calciferols. In biochemistry, vitamin D metabolites belong to the group of secosteroids which are similar to steroid hormones.
The sun hormone
UVB rays with a wave length of 280-315 nm transform pro-vitamin D in pre-vitamin D. In further steps, vitamin D is built in kidneys and liver.
To a certain degree, our body can store the vitamin in muscles and fatty tissue.
Basically, however, vitamin D supply is a question of way of life. The solution: day light or sun light with a sufficient percentage of UV on naked skin.
That does not mean sun bathing. A short UVB exposition is enough to build sufficient vitamin D. When hands, arms and forearms are exposed to sun for the period of half the minimal erythema dose two or three times weekly, skin has the possibility to produce vitamin D from pro-vitamin D. The minimal erythema dose, according to skin type, is 5 to 40 minutes; that means skin’s own protection period until it begins to redden.
From pro-vitamin D, 7-dehydrochlesterol, skin builds pre-vitamin D, cholecalciferol, that finally is further transformed to vitamin D, calciferol.
The sun determines the dose of sun hormone.
Self-regulation means that pre-vitamin and vitamin D, in case they are not directly required and further transported in the blood, are degraded to ineffective products. That prevents vitamin D overdose.
Due to this self-regulation, with a short period of UVB exposure the amount of vitamin D production is similar to the amount with exposure over a longer period of time.
Pro-vitamin D: benefits
Pro-vitamin D is a natural component of skin and a precursor in the biosynthesis of cholesterol and vitamin D. Pro-vitamin D regulates the differentiation of skin cells and stimulates the production of skin’s own antimicrobial peptides. Pro-vitamin D, with the chemical term 7-dehydrocholesterol, protects keratinocytes against UVB damages.
If pro-vitamin D is applied to skin, the protein level and the quantity of mRNA for heat shock proteins increase, thereby raising the minimal erythema-effective UVB dose. Pro-vitamin D is also involved in the building of the cornified envelope of skin and full development of corneocytes.
As vitamin D production in skin starts from pro-vitamin D, the topic application of pro-vitamin D has several positive effects on skin, whether improvement of the cornified envelope and barrier function or cell differentiation and activation of antimicrobial peptides as well as protection from UV rays, protection of hair follicles or promotion of melanocyte synthesis.
Moreover, pro-vitamin D has the advantage that skin can use it for vitamin D synthesis in a self-regulation way.
Do high light protection filters inhibit vitamin D production?
The Robert Koch Institute informs that even sun protection filters from factor 20 do block up UVB radiation up to 95% and therefore could induce less or slower vitamin D production. The effect can be compensated for with a somewhat longer stay in the sun.
A study at the John Hopkins University (Journal of the European Academy of Dermatology and Venerology, 2020: Prevalence and correlates of sun protection with sunburn and vitamin D deficiency in sun-sensitive individuals) also dealt with the question. The result: Persons with fair, sensitive skin who frequently used sun protection products and staid in the shadow showed no higher probability for vitamin D deficiency.
The combination of sun protection filters and other sun protection measures, e.g., staying in the shadow, can make sense to prevent the risk of skin damages and vitamin D deficiency.
Pro-vitamin D and sun protection: clever combination
In spring and summer, the days are longer and we probably receive enough UVB-containing sun rays, while in autumn and winter, shorter days diminish the sun light occasion. Therefore, a day cream with UV-filters for spring/summer and a day cream without UV-filters but with pro-vitamin D, 7-Dehydocholesterol, seems to be a cosmetic concept corresponding to the seasonal position of the sun and skin’s ability for vitamin D synthesis from pro-vitamin D.
Pro-vitamin D for use in skincare is derived from cholesterol (e.g., from sustainably produced sheep’s wool). We detect it from following companies, e.g.:
- Evonik: INCI: 7-Dehydrocholesterol, trade name: TEGO Sterol 7-DHC
- MMP Europe: INCI: 7-Dehydrocholesterol, trade name: Skin’ential DC
- Labio Co., Ltd.: INCI: Glycerin, Methyl Cyclodextrin, Aqua, 7-Dehydrocholesterol, trade name: Aqua-pro Vita D3
With or without sun:
Literature
Sunscreen photoprotection and vitamin D status.
Passeron T, Bouillon R, Callender V, Cestari T, Diepgen TL, Green AC, van der Pols JC, Bernard BA, Ly F, Bernerd F, Marrot L, Nielsen M, Verschoore M, Jablonski NG, Young AR.Br J Dermatol. 2019 Nov;181(5):916-931
Young AR, Narbutt J, Harrison GI, Lawrence KP, Bell M, O’Connor C, Olsen P, Grys K, Baczynska KA, Rogowski-Tylman M, Wulf HC, Lesiak A, Philipsen PA.Br J Dermatol. 2019 Nov;181(5):1052-1062
Hawk JLM.Photodermatol Photoimmunol Photomed. 2020 Nov;36(6):417-423
Evaluation of vitamin D plasma levels after mild exposure to the sun with photoprotection.
Pereira LA, Luz FB, Carneiro CMMO, Xavier ALR, Kanaan S, Miot HA.An Bras Dermatol. 2019 Jan-Feb;94(1):56-61
Do sunscreens block vitamin D production? A critical review by an international panel of experts.
Bikle DD.Br J Dermatol. 2019 Nov;181(5):884