Vitamin D, often referred to as the “sunshine” vitamin, has attracted significant attention over the past decades due to a considerable proportion of the global population being deficient in this essential nutrient. Initially known for its importance in bone formation, increasing evidence suggests that vitamin D plays a role in the proper function of various tissues in our bodies, including the brain, heart, muscles, immune system, and skin. As a result, its deficiency has been linked to a wide range of diseases, such as cancers, autoimmune disorders, cardiovascular conditions, and neurological disorders. In this review, we will focus on the dermatological perspective of this disputed vitamin and its impact on the skin.
Sources of Vitamin D
There are three primary sources of vitamin D: sunlight, dietary intake, and vitamin D supplements. Sun exposure is a well-known source of vitamin D, as the skin synthesizes it when exposed to sunlight. Historically, the effect of sunlight on vitamin D was observed when comparing the fragile skulls of Persians (who covered their heads from sunlight) to the stronger skulls of Egyptians (who exposed their heads to sunlight). This process of vitamin D synthesis in the skin occurs through UVB radiation, converting 7-dehydrocholesterol to previtamin D3, which is eventually released into the bloodstream.
Diet and supplements are the other sources of vitamin D. Some natural dietary sources include cod liver oil, cheese, egg yolks, fatty fish like mackerel and salmon, tuna fish, and beef liver. However, it can be challenging for many individuals to obtain adequate vitamin D from their diet alone, so foods like milk, orange juice, yogurt, and cereal are often fortified with vitamin D. Additionally, vitamin D supplements in the form of vitamin D2 or D3 are readily available over-the-counter.
Vitamin D Levels: There have been different cutoff values used to define normal thresholds for vitamin D levels. In the past, a level of 50 nmol/L was often considered insufficient, while some studies used 37.5 nmol/L as the minimum level of sufficiency. However, recent evidence suggests that an optimal vitamin D level should be 75 nmol/L or higher to cover all physiological functions of vitamin D.
Factors Influencing Vitamin D Levels: Various factors can influence vitamin D levels in the body. Nutrient deficiencies, limited sun exposure, impaired kidney function (which affects conversion to the active form of vitamin D), and inadequate absorption from the digestive tract can all lead to vitamin D deficiency. Diets lacking in vitamin D-rich foods can be associated with specific dietary choices, such as milk allergy, lactose intolerance, ovo-vegetarianism, and veganism.
Synthesis of Vitamin D3 in the Skin: The production of vitamin D in the skin is influenced by environmental factors like latitude, season, time of day, weather conditions, air pollution, and surface reflection, all of which affect the amount of UVB radiation reaching the skin. Personal factors, such as age (elderly people have thinner skin, reducing vitamin D synthesis) and obesity (overweight individuals may have lower vitamin D levels), can also play a role. Skin type is another important factor, as lighter skin types (type I) can produce up to six times more vitamin D than darker skin types (type VI). Lifestyle choices, clothing habits, and sun avoidance practices also impact vitamin D synthesis.
https://pubmed.ncbi.nlm.nih.gov/22425213/
7-Dehydrocholesterol is converted to previtamin D3 in the basal (stratum basale) and suprabasal layers of the epidermis of the skin.
Certain practices, like using sunblocks and sunbeds, can also influence vitamin D production. Sunblocks effectively block UVB radiation, but their impact on vitamin D deficiency remains uncertain, as certain areas of the skin may still be exposed. Regular use of tanning beds emitting UVB radiation may lead to higher 25(OH)D concentrations, but there are concerns about their potential link to skin cancer.
To synthesize Vitamin D3 in the skin, a few conditions must be met, including an UV index of more than 3. The World Health Organization advises getting 5 to 15 minutes of casual sun exposure to the hands, face (although I don’t recommend exposing your face to the sun for Vitamin D production; instead, focus on other parts of your body like legs and arms) two to three times a week during the summer months. This kind of sun exposure as you go about your daily life can make a significant difference in Vitamin D production
Vitamin D3 is produced in our body from cholesterol and is considered a steroid hormone known as 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). It belongs to a group of fat-soluble vitamins, which means that we need fats and cholesterol in the skin to produce Vitamin D3. It’s essential to note that reducing cholesterol may not always be the best solution; instead, the key is to balance cholesterol levels to support optimal Vitamin D synthesis.
Maintaining a healthy balance of cholesterol and fats in your diet is crucial for the production of Vitamin D3 in your skin. It’s important to understand that your body needs these components to efficiently produce the vitamin, supporting overall well-being and various vital functions in the body. So, don’t shy away from healthy fats and ensure you get moderate sun exposure to support adequate Vitamin D levels. As always, consult with your healthcare provider for personalized advice on maintaining a balanced diet and getting the right amount of sun exposure for your individual needs.
Overall, vitamin D plays a crucial role in various bodily functions, and its deficiency can have significant implications for overall health, including dermatological health. Addressing and managing vitamin D deficiency is essential to promoting better health outcomes.
Vitamin D has a wide range of functions in the skin, affecting differentiation, immunity, antimicrobial activity, photoprotection, and the pathogenesis of various skin diseases. However, further research is needed to fully understand the complex interactions between vitamin D and the skin and its potential therapeutic applications for skin conditions.
- Skin Differentiation and Proliferation: Vitamin D plays a crucial role in regulating the skin differentiation process. It increases the expression of certain proteins and structures in keratinocytes while inhibiting proliferation, leading to the formation of the cornified envelope and promoting skin differentiation.
- Cutaneous Antimicrobial Effects: Both vitamin D and its receptor (VDR) regulate the skin barrier formation and induce the innate immune response in the skin. They activate receptors that lead to the induction of antimicrobial peptides, which are responsible for killing invasive organisms.
- Vitamin D and Cutaneous Innate Immunity: Vitamin D has a historical link with innate immune function and has been shown to modulate gene expression in response to bacterial challenges, leading to enhanced bacterial killing.
- Vitamin D and Cutaneous Adaptive Immunity: Vitamin D influences T-cell cytokines, leading to the modulation of cytokine production by T cells. It can suppress Th1 cytokines and promote Th2 cytokines, as well as induce regulatory T cells (Tregs) that suppress immune responses by other T cells.
- Hair Follicle Cycling: Vitamin D and its receptor (VDR) have roles in the postnatal maintenance of the hair follicle, and VDR activation is associated with hair cycle progression.
- The Sebaceous Gland: Vitamin D’s effects on sebaceous glands may be related to growth regulation and other cellular functions in these glands.
- Photoprotection: Vitamin D has been found to exhibit photoprotective effects in the skin, including reduced DNA damage, apoptosis, and erythema caused by ultraviolet (UV) light.
- Wound Healing: Vitamin D regulates the expression of cathelicidin, an antimicrobial protein that promotes wound healing and tissue repair.
- Vitamin D and Skin Diseases: Vitamin D deficiency has been implicated in various skin disorders, including skin cancer, psoriasis, acne, hair loss, vitiligo, and atopic dermatitis.
- Skin Cancer: Vitamin D may have a protective effect against certain skin cancers, and its deficiency has been linked to increased skin cancer risk in some studies.
- Psoriasis: Vitamin D deficiency may contribute to psoriasis pathogenesis, and topical calcipotriol (a vitamin D analog) is used in the treatment of psoriasis.
- Acne and Rosacea: Vitamin D may play a role in modulating acne by inhibiting Th17 differentiation. However, the association between vitamin D levels and rosacea is still not fully understood.
- Hair Loss: Vitamin D and VDR may have roles in hair follicle cycling and hair loss. Studies have shown associations between vitamin D levels and various types of hair loss.
- Vitiligo: Vitamin D may protect the epidermal melanin unit and restore melanocyte integrity in vitiligo patients. Some studies have shown an association between vitamin D deficiency and vitiligo.
- Pemphigus Vulgaris and Bullous Pemphigoid: Vitamin D deficiency has been observed in patients with these autoimmune bullous disorders.
skinscalpcoach.com 
Leave a comment