Provitamin D: Precursor to the sun hormone
Vitamin D controls important metabolic functions in the body. It has positive effects on bone formation and density, the formation of bone stem cells, the immune system, the musculature, the skin and the psyche.
Recently, other effects have been discussed, but they are not clearly confirmed scientifically. For example, it is not yet possible to say with certainty whether vitamin D protects against severe COVID. It does not seem to play a role in the prevention of cancer and cardiovascular disease.
As essential as vitamin D is to health, it is not a miracle cure. Those who want to take special vitamin supplements should have their vitamin D levels tested by a doctor beforehand.
Dietary supplement or light?
In fact, many Central Europeans have low vitamin D levels. In addition to spending too little time outdoors in daylight, older age, metabolic disorders, certain medications or diseases can impair vitamin D synthesis.
Full-face veiling also impedes vitamin D synthesis. People with strong skin pigmentation and consequently dark skin color need more UVB radiation to produce vitamin D; on the other hand, they usually have a higher bone density.
Even though in some countries certain foods are fortified with vitamin D, only part of it, 10-20 percent, is absorbed through food.
Vitamin D2 is supplied by plant sources, such as cashews, mushrooms dried in sunlight if possible. D3 comes from animal sources, such as sea fish, eggs, milk. If the milk comes from cows with plenty of pasture and sunlight in the barn, it has a vitamin D content sufficient for one glass of milk a day to provide the body with enough to produce on its own.
80 -90 percent is produced by the body itself with the help of sunlight, which is why vitamin D is also known as the sun hormone.
Vitamin D is a generic term for fat-soluble vitamins, the so-called calciferols. Biochemically, vitamin D metabolites belong to the group of secosteroids, which are similar to steroid hormones.
The sun hormone
UVB rays of a wavelength of 280-315 nm convert the provitamin D into pre-vitamin D. In further steps, vitamin D is formed via kidney and liver.
To a certain extent, the body can store the vitamin in muscle and fat tissue.
Basically, however, vitamin D supply is a lifestyle issue. The solution is daylight or sunlight with a sufficient UVB component on uncovered skin.
This does not require sunbathing. A short UVB exposure is already enough to produce enough vitamin D. Exposing hands, arms, and forearms to the sun two to three times a week for half the minimum erythema dose gives the skin an opportunity to build vitamin D from pro-vitamin D. The minimum erythema dose is 5 – 40 minutes depending on the skin type and means the self-protection time of the skin until redness appears.
From the provitamin D, 7-dehydrochlesterol, the skin forms the pre-vitamin D, cholecalciferol, which is eventually further converted to vitamin D, calciferol.
The sun makes the dose of the sun hormone.
Self-regulation means that pre-vitamin D and vitamin D, if not immediately needed and passed with the blood, are broken down into ineffective products. This prevents vitamin D oversupply.
Due to this self-regulation, a short exposure to UVB rays produces a similar amount of vitamin D as comparable radiation over a longer period of time.
Provitamin D: Advantages
Provitamin D is a natural component of the skin and a precursor in the biosynthesis of cholesterol and vitamin D. Provitamin D regulates skin cell differentiation and stimulates the formation of skin antimicrobial peptides. Provitamin D, with chemical name 7-dehydrocholesterol, protects keratinocytes against UVB damage.
When provitamin D is applied to the skin, protein levels increase, as does the amount of mRNA for heat shock proteins, which increase the minimum erythema-effective UVB dose. Provitamin D is also involved in the formation of the corneal envelope of the skin and the maturation of corneocytes.
Since vitamin D formation in the skin originates from provitamin D, topical application of provitamin D has quite a few beneficial effects on the skin, from improving the corneal envelope and barrier function, to cell differentiation and activation of antimicrobial peptides, to protecting against UV rays, protecting hair follicles, and supporting melanocyte formation.
In addition, provitamin D offers the advantage that the skin can use it in a self-regulating manner for vitamin D synthesis.
Can high light protection filters inhibit vitamin D formation?
Information from the Robert Koch Institute indicates that sunscreen filters with a factor of 20 or higher block about 95% of UVB radiation, which means that less vitamin D is formed, or at a slower rate.
This can be compensated for by the fact that sunscreen filters allow us to stay in the sun a little longer.
A study at John Hopkins University (Journal of the European Academy of Dermatology and Venerology, 2020: Prevalance and correlates of sunprotection with sunburn and vitamin D deficiency in sun-sensitive individuals) also addressed this question. According to the study, people with white, sensitive skin who used sunscreen more frequently and stayed in the shade were not more likely to have vitamin D deficiency.
So, combining sunscreen filters with other sun protection measures, such as staying in the shade, can be useful in avoiding the risk of skin damage and vitamin D deficiency.
Provitamin D and sun protection: Cleverly combined
Since we get enough UVB-containing sun rays in spring and summer due to the longer days, while in fall and winter the shorter days give us less opportunity, a day cream with UV protection for spring/summer and a day cream without UV protection containing provitamin D, 7-dehydocholesterol, would be a cosmetic concept in line with the seasonal course of the sun and our skin’s ability to synthesize vitamin D from provitamin D.
Provitamin D for use in skin care is derived from cholesterol (e.g., from sustainably produced sheep’s wool). We can find it from the following manufacturers, for example:
- 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: Cosmacon develops day creams with provitamin D without sun protection and day creams with sun protection, so that your skin is always sufficiently supplied with the sun hormone.
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