Sunlight exposure is the primary source of vitamin D for most people in South Asian countries like Sri Lanka. Solar ultraviolet-B radiation (UVB; wavelengths of 290 to 315 nanometers) stimulates the production of vitamin D3 from 7-dehydrocholesterol (7-DHC) in the epidermis of the skin. Hence, vitamin D is actually more like a hormone than a vitamin; a substance that is required from the diet. Vitamin D3 enters the circulation and is transported to the liver, where it is hydroxylated to form 25-hydroxyvitamin D3 (also known as: Calcifediol; the major circulating form of vitamin D). Then, in the kidneys, the 25-hydroxyvitamin D3-1-hydroxylase enzyme catalyzes a second hydroxylation of 25-hydroxyvitamin D, resulting in the formation of 1, 25-dihydroxyvitamin D3 (calcitriol, 1α, 25-dihydroxyvitamin D) – the most potent form of vitamin D. Most of the physiological effects of vitamin D like photoprotection and wound healing in the body are related to the activity of 1, 25-dihydroxyvitamin D3. Keratinocytes in the epidermis possess hydroxylase enzymes that locally convert vitamin D to 1,25-dihydroxyvitamin D3 the form that regulates epidermal proliferation and differentiation. So, when vitamin D is deficient in human bodies our overall immunity against various pathogens goes down. Subsequently, low immunity causes various skin problems.
Functions of Vitamin D in the human skin
- Photoprotection – mechanisms that help living organisms to cope with molecular damage caused by UV sunlight. Photodamage refers to skin damage induced by ultraviolet (UV) light. Currently, due to the damage of Earth’s ozone layer, all species of this planet has to face increasing amount of UV radiation. Depending on the dose, UV light can lead to DNA damage, inflammatory responses, skin cell apoptosis (programmed cell death), skin aging and skin cancer. Some studies, mainly in vitro (cell culture) studies and mouse studies where 1, 25-dihydroxyvitamin D3 was topically applied to skin before or immediately following irradiation have found that vitamin D exhibits photoprotective effects. Documented effects in skin cells include decreased DNA damage, reduced apoptosis, increased cell survival and decreased erythema (redness). The mechanisms for such effects are not known, but one mouse study found that 1,25-dihydroxyvitamin D3 induced expression of metallothionein (a protein that protects against free radicals and oxidative damage) in the stratum basale of the skin. It has also been assumed that non-genomic actions of vitamin D contribute to the photoprotection; such effects of vitamin D involve cell-signaling cascades that open calcium channels.
- Wound healing – 1,25-dihydroxyvitamin D3, the active metabolite of vitamin D, regulates the expression of cathelicidin, an antimicrobial protein which helps in mediating innate immunity in skin by promoting wound healing and tissue repair. One human study found that cathelicidin expression is upregulated during early stages of normal wound healing. Other studies have shown that cathelicidin modulates inflammation in skin, induces angiogenesis and improves reepithelialization (the process of restoring the epidermal barrier to re-establish a functional barrier that protects underlying cells from environmental exposures). However, more research is needed to determine the role of vitamin D in wound healing and epidermal barrier function and whether oral vitamin D supplementation or topical treatment with vitamin D analogs is helpful in healing surgical wounds.
Correlation between acne and Vitamin D
While hormonal imbalance and overall hygiene are primary causes of acne, a poor immune system due to low amounts of vitamin D in your system can also increase oil production in your skin cells. Overactive sebaceous glands can produce too much oil and combine with skin cells to plug pores. When the pores in the skin become plugged, bacteria on the skin multiply, causing skin lesions. These blocked, oil-producing lesions lead to the unsightly blemishes that can afflict the skin at any time of a human’s life. When the human body lacks sufficient amounts of Vitamin D, immunity is severely impaired. Consequently, the body lacks the ability to fight with pathogenic bacteria residing in the clogged sebaceous glands. When the body has sufficient amounts of Vitamin D, it reduces the amount of bacteria in your system by boosting your immune system, reducing the level of acne.
Vitamin D and Psoriasis
According to Mayo Clinic, Psoriasis is a common skin condition that changes the life cycle of skin cells. Psoriasis causes cells to build up rapidly on the surface of the skin. The extra skin cells form thick, silvery scales and itchy, dry, red patches that are sometimes painful. When you have psoriasis, there is a thick, patch like, layer of dry skin cells on the outer layer of your skin. It can be itchy. There are different kinds of psoriasis — and the condition is associated with a poor immune system, where in certain instances, low vitamin D levels. The “Journal of Investigative Dermatology” showed that when exposed to ultraviolet-B rays, the element of sunlight that kick starts the vitamin D production system in the body, vitamin D levels increased significantly and the symptoms of psoriasis disappeared. Similarly, a study in “Rheumatology International” also found that increasing vitamin D levels helped to improve psoriasis symptoms.
Vitamin D Deficiency
Sunlight is a resource found in plenty in tropical countries like Sri Lanka. These tropical countries that close to the equator are blessed with bountiful sunlight throughout the year. Yet, due to social stigma about skin color and various reasons, we often cover our exposed skin from sunlight. Also, due to increased harmful UV radiation in the sunlight we are forced to shield our skin against it. In addition to reduced amounts of sunlight for our skin, our modern diets are filled with oily fast food lack in many essential nutrients; including vitamin D. So, in the general population, vitamin D deficiency is a growing threat that is often ignored. A study conducted in United States in 2010 confirmed that 42% of U.S adults were vitamin D deficient. Currently experts suggest, Vitamin D insufficiency affects almost 50% of the population worldwide. An estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency (VDD). This pandemic of hypovitaminosis D can mainly be attributed to lifestyle (for example, reduced outdoor activities) and environmental (for example, air pollution) factors that reduce the exposure to sunlight.
Vitamin D supplementation
Sunshine vitamin or in other terms vitamin D is immensely important for prevention of chronic diseases including skin conditions. High prevalence of vitamin D insufficiency is a particularly important public health issue because lack of vitamin D is an independent risk factor for total mortality in the general population.
Even though, our main source of vitamin D is sunlight, we cannot seek the sun for vitamin D. The American Academy of Dermatology does not recommend getting vitamin D from sun exposure (natural) or indoor tanning (artificial) because ultraviolet (UV) radiation from the sun and tanning beds can lead to the development of skin cancer. Skin cancer is the most common cause of cancer in United States. It is estimated that one person dies from melanoma, the most serious form of skin cancer, every hour in the United States. So, it is clear that due to environmental pollution, it is impossible to absorb sufficient amounts of vitamin D from sunlight.
So, one might ask how can we gain essential amounts of vitamin D without sunlight?
Answer is pretty simple. Getting vitamin D from a healthy diet, which includes naturally enriched vitamin D foods, fortified foods and beverages, and/or vitamin supplements, and practicing sun protection offer a healthier and safer alternative. Dietary sources (foods naturally rich in vitamin D, fortified foods and beverages) and vitamin supplements are available all year-round and can easily be incorporated into a healthy lifestyle. Good sources include fortified milk, cheeses and yogurt, fortified cereal, and oily fish like salmon and tuna. Research shows that vitamin D supplements are well tolerated, safe and effective when taken as directed by a physician. It is also suggested to measure the serum 25-hydroxyvitamin D level as the initial diagnostic test in patients at risk for deficiency.
Based on currently available scientific evidence that supports a key role of calcium and vitamin D in skeletal health, the IOM Recommended Dietary Allowance (RDA) for vitamin D is:
- 400 IU (International Units) for infants/children 0-1yr
- 600 IU for children, teenagers and adults 1-70yr
- 800 IU for adults 71+ yr
It is very important to anyone to be concerned about getting enough vitamin D and he or she should discuss with his or her doctor about the options for obtaining sufficient vitamin D from foods and/or vitamin supplements.
As the amount of vitamin D a person receives from the sun is inconsistent and increases the risk of skin cancer, the IOM’s RDA was developed based on a person receiving minimal or no sun exposure.
In conclusion, research shows that vitamin D is a key player in preventing various skin problems. Not just skin problems the “sunshine vitamin” is essential for overall well-being of a human. So understanding the importance of this wonderful vitamin, which is often ignored or taken for granted, can create a healthier, and happier population.
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