Vitamin D

To sit outside in the sun or not to sit outside in the sun—that is the perennial question we ask ourselves when torn between protecting our skin from UV damage or getting our recommended daily amount of vitamin D. But with all the other methods available, like through diet, oral supplements, or topicals, how necessary is baking in the sun? (Spoiler: it isn't, and will never be.) . 

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin and one of the most critical vitamins for biological function. Our skin is an important natural reservoir for its production, triggered by UV light into synthesis. Dhingra breaks it down: Our gut (via diet) and skin (via sunlight) are the two main sources of vitamin D, which is made in two forms—vitamin D3 in the skin and D2 and D3 in the gut—both of which are further modified by our kidneys. Needless to say, inadequate sunlight exposure and poor diet are the two most common reasons for vitamin D deficiency.1

"Someone’s ability to manufacture vitamin D also depends on a person’s skin type (color), sex, body mass index, physical activity, alcohol intake, and vitamin D receptor polymorphisms (variances, which are genetic)," Herrmann says. It's tricky to say how much vitamin D each person needs because it varies with climate, time of year, skin color, and diet, but according to the National Institutes of Health, the average (non-deficient) adult should aim for 600 International Units (IU) per day in their diet. Look to fortified foods like milk as well as salmon, eggs, and mushrooms as great food sources of vitamin D.

Dhingra says the chief function of vitamin D is maintaining a calcium balance in our bodies, but it also has functions well beyond this—for instance, the role it plays in skin health. As Zeichner puts it, "Generally speaking, skin health is best improved when your body has a full store of vitamin D." Below are the main ways vitamin D benefits the skin.

• Decreases inflammation: "The most important practical use of Vitamin D in the skin to date is as a mild-to-moderate anti-inflammatory, used clinically as a cream in the treatment of conditions like psoriasis, eczema, and vitiligo," Dhingra says. "Vitamin D dials down exuberant inflammation, alleviating symptoms for those suffering from these conditions."
• Protects the skin: Dhingra adds that vitamin D functions as a steroid, working within a cell’s nucleus to stimulate proliferation, regulate function, and potentially stabilize genes. A 2012 study suggests that Vitamin D may play a protective role in cancers broadly, and skin cancer specifically.2
• Decreases environmental damagers: Herrmann and Gerstner say as an antioxidant, topical vitamin D can also squelch damaging environmental oxidants that cause premature aging.
• Normalizes cell turnover: Zeichner says vitamin D analogues have been shown to normalize cell turnover and prevent the build-up of dead cells on the skin's surface that lead to psoriasis plaques.

Side Effects of Vitamin D

Zeichner says topical vitamin D is generally safe to use daily, but like any skincare product, Dhingra says it could cause irritation, depending on how it’s created. Herrmann warns that many of these products are oil-based, which could be too heavy in acne-prone skin and cause pore-clogging.

When taken orally, Dhingra says it’s fairly difficult to consume a significantly excessive amount of vitamin D but that the fat-soluble vitamin can cause excess calcium buildup with nausea, vomiting, mental changes, increased urination, and kidney failure. "This is only ever in the setting of extreme supplementation, which should only be done with a qualified medical professional," Dhingra says. In general, Gerstner recommends not exceeding 4,000 IU a day, but always check with your physician and discuss any supplements or vitamins before adding them to your regimen.

How to Take/Apply It

When taking a vitamin D supplement, Zeichner recommends doing so along with a fatty meal (healthy fats, that is) for best absorption.

If using a topical vitamin D prescription, follow the application instructions from your doctor. If you choose to use a topical vitamin D for anti-aging, Herrmann says combining it with other antioxidant vitamins, growth factors, or retinoids can create a "super" product, working on multiple anti-aging pathways. 

Vitamin D can also be found in some OTC beauty products. "Medically, I often use a prescription cream-based vitamin D analogue to maintain clearness for psoriasis and other inflammatory skin diseases," Dhingra says. However, Dhingra adds that outside of its clinical uses in fighting inflammatory skin diseases, the evidence is not concrete enough to strongly recommend everyone implement a vitamin D-based product in their skincare line for normal skin health.

For sun-stimulated vitamin D, Dhingra says sunscreen is critical, as well as limiting exposure to no more than 10 to 15 minutes daily, and minimizing the amount of skin you expose.

Other Forms

Herrmann says all methods (injectable, oral, topical, and sun-stimulated) of vitamin D are effective for skin health but adds that a true deficiency is more easily treated by injectable or oral supplementation.

According to Zeichner, daily vitamin D supplementation (via either diet or nutritional supplements) is an effective way to replenish low vitamin D levels and is a safer option than sun exposure. "This approach has numerous clear-cut health benefits without an increased risk of premature wrinkles or skin cancer," Dhingra says. If you're concerned that you might be deficient, Williams says to consult your board-certified dermatologist to have your vitamin D level checked with a blood test to determine the appropriate dosage.

Finally, let's address the controversial method of sun exposure. Is it possible to get enough vitamin D from the sun while still protecting yourself from skin cancer? The derms say yes. As Zeichner explains it, our bodies naturally make vitamin D in response to sun exposure. However, the amount you need to produce adequate vitamin D is quite low. "In fact, incidental sunlight exposure, even when you are wearing sunscreen, is enough," Zeichner says. "It is a total myth that you need to sunbathe to increase your vitamin D levels." Need some more convincing? Dhingra further explains it: Essentially, sunlight exposure can be measured by how much it takes to cause your skin to turn slightly pink a day after exposure, which will clearly vary depending on how much melanin your skin possesses. According to Dhingra, your body will hit max production of skin-based vitamin D well before this, so baking at the beach is certainly not necessary.