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Vitamin D, or the so-called sunshine vitamin, is an essential nutrient, playing a major role in regulating the function of almost every tissue in our bodies, including our bones, muscles, brain, heart, and skin. Nevertheless, research suggests that a significant portion of the worldwide population (about 1 billion people) is vitamin D deficient, making it a hot topic over the past decades and raising the interest in the best methods to achieve its optimal levels.
In this article, we'll take a deeper look into this essential vitamin and discuss the correlation between its low levels and skin disorders.
What Is Vitamin D and Why Is It So Important?
Even though it's referred to as a vitamin, vitamin D is, in fact, not a vitamin but a fat-soluble prohormone, occurring in two main forms – ergocalciferol (or vitamin D2) found in plants and cholecalciferol (or vitamin D3) found in animal-based foods. In humans, the primary source of vitamin D is obtained from sunlight. Specific wavelengths of UVB rays are transformed into pre-vitamin D inside the skin, which is then changed into Vitamin D3 or cholecalciferol [source].
Vitamin D has crucial endocrine and cellular functions in our bodies [source]. The endocrine function of vitamin D refers to maintaining healthy calcium levels in the blood. Vitamin D and calcium work closely together – vitamin D helps the body efficiently absorb calcium from the intestines, while calcium helps build healthy bones and other tissues.
The cellular functions of vitamin D refer to the paracrine and autocrine functions, including the inhibition of cell proliferation (cell growth and division), the promotion of cell differentiation (cell development and maturity, from embryonic cells to mature cells with specific forms and functions), and apoptosis (the programmed cell death important for eliminating pre-cancerous cells).
Therefore, vitamin D plays a crucial role in maintaining many organ systems, promoting a healthy immune system, and preventing cancer. In other words, sufficient levels of vitamin D help with bone loss, depression, diabetes, cardiovascular diseases, weight loss, multiple sclerosis or MS, cancer prevention, as well as skin health.
How Vitamin D Affects the Skin
Research shows that vitamin D plays a major role in the skin – it works closely with the keratinocytes, the most prominent cell type in the epidermis. These are the only cells in the skin and the whole body that are able to synthesize vitamin D from its precursor and have the necessary enzymes to metabolize vitamin D into its active form. Through the interaction with these cells, vitamin D plays a vital role in skin physiology, including:
Epidermal differentiation and proliferation – Vitamin D inhibits the proliferation of the keratinocytes and promotes their differentiation. Cell proliferation refers to increasing the number of cells, while cell differentiation is the process of creating new cell types with specialized functions. Through this mechanism, vitamin D creates the necessary cell homeostasis and prevents the uncontrollable cell growth that may result in skin cancer;
Maintaining the epidermal barrier function – A proper barrier function is vital for keeping the water inside the skin and pollutants and other aggressors out. Vitamin D plays a significant role in maintaining this function by synthesizing the structural proteins inside the epidermis and facilitating the formation of lipids (or ceramides) inside the barrier;
Inducing the keratinocyte apoptosis – Cell apoptosis refers to programmed cell death, which mainly occurs in the early development to eradicate unwanted cells. Vitamin D promotes keratinocyte apoptosis, regulating epidermal formation and inhibiting carcinogenesis. The keratinocyte apoptosis plays a critical role in balancing cell proliferation, maintaining the thickness and formation of the stratum corneum, and eliminating pre-cancerous cells;
Regulating the skin immune functions – Vitamin D modulates cytokine production by keratinocytes. Cytokines are small proteins or peptides that are crucial in controlling the growth and function of other blood cells as well as immune cells. Therefore, they regulate the body's immune and inflammation processes.
Skin Signs of Low Vitamin D
Here are the most common skin disorders that are associated with vitamin D deficiency:
Psoriasis is an inflammatory skin disease that causes itchy, scaly, and red patches on the skin. It's a chronic disease that goes through cycles, flaring up for a certain period (weeks or months) and then subsiding. So far, there's no cure for psoriasis, but the symptoms can be managed with topical forms of vitamin D.
There's no apparent connection between vitamin D deficiency and psoriasis. However, some studies suggest that the loss of anti-inflammatory activity and the loss of anti-proliferation and anti-angiogenic (keeping new blood vessels from forming) functions of vitamin D could cause this skin disorder.
Eczema or atopic dermatitis is another common inflammatory skin disease caused by vitamin D deficiency. Like psoriasis, it typically manifests itself in red, dry, and itchy skin that tends to flare up and subside periodically. Studies suggest that this is caused by the disrupted epidermal barrier function as well as the unbalanced skin's immune system due to the lack of vitamin D.
Acne vulgaris is the most widespread skin disorder affecting millions of people around the world. It is also a chronic skin disease that involves blockage and inflammation of hair follicles and sebaceous glands.
Studies suggest that there are many ways in which the lack of vitamin D may influence the formation of inflammatory acne. First off, it may be caused by the reduced synthesis of interleukin, a type of protein that regulates immune responses and has anti-inflammatory properties.
Furthermore, when vitamin D levels are insufficient, the sebaceous glands secret more fats, providing a breeding ground for acne-causing bacteria, P. acnes, and causing inflammatory acne lesions.
Vitiligo is a skin condition that causes the skin to lose color or pigment in patches due to the loss of its pigment cells or melanocytes. These discolored patches can occur in various body parts, including skin, scalp, and mucous.
Through various mechanisms, vitamin D significantly affects melanocytes and keratinocytes in the epidermis [source]. However, the exact way in which vitamin D affects melanocytes, cells that produce pigment or melanin, is still unclear. Nevertheless, studies suggest that topical application of vitamin D yields great results in treating vitiligo as it reduces the expression of vitiligo-causing cytokines and prevents the destruction of melanocytes.
Studies show that vitamin D deficiency can cause hair loss or alopecia, an autoimmune disorder that causes shedding and bald patches on the scalp as well as other areas of the body in both men and women.
Vitamin D plays a crucial role in the proliferation and differentiation of keratinocytes, skin cells that produce keratin, an essential protein for healthy skin, nails, and hair. The lack of vitamin D in the body disrupts the normal functioning of keratinocytes in hair follicles, causing irregularities in hair cycling that lead to hair loss and shedding.
The Best Sources of Vitamin D
The significant sources of vitamin D are sunlight, food, and supplements. However, too long sun exposure, especially without proper protection, can have negative consequences, like premature skin aging and, in the worst-case scenario, skin cancer. Therefore, try to avoid the sun when it's at its hottest; instead, get your 15-minute dose of sunlight early in the morning. And of course, always wear sunscreen with an SPF of at least 30.
Vitamin D is also found in certain foods, such as liver, red meat, oily fish (like salmon and mackerel), cereal, egg yolk, and mushrooms. So make sure to get enough of these foods, especially during winter, when there's not enough sunlight.
And the third option to get enough vitamin D is through dietary supplementation. But even though you can find vitamin D supplements over-the-counter, it would be best to talk to your doctor before taking them to ensure the proper dosage. Bear in mind that too much vitamin D can cause hypercalcemia, high calcium levels in the blood, causing significant damage to the bones, kidneys, and heart.
All in all, vitamin D is essential for skin health, and its deficiency may cause severe skin disorders. It plays a vital role in skin cell growth and repair, protecting the skin from damage and preventing premature aging.
Besides inflammatory skin disorders and hair loss, other common vitamin D deficiency symptoms that people report are muscle and bone pain. In addition, depression, constant fatigue, and weakened immunity often indicate low vitamin D. Therefore, for the sake of your overall health as well as your beauty, make sure to get enough of this vitamin.