It can often take a lot of time and research to get to the bottom of a mysterious skin concern—but sometimes it just happens accidentally, like the day my dermatologist casually alerted me to my vitamin D deficiency based on nothing but the clues I dropped during a routine exam.
I was in her office for my regular mole check, rambling away while she carefully reviewed every freckle on my body. I told her how I'd been handling quarantine life and how much I missed eating cheese (I was on a dairy-free diet at the time). We chatted about my family and my job, and I shared this embarrassing new development where every time I scratched my head, I ended up with flakes in my hair and dead skin under my nails.
"How's your vitamin D?" she asked immediately. (Apparently, it was the combination of my very dry skin, the mention of a low-calcium diet, the assumption that I was spending a lot of time indoors, and the sudden onset of dandruff that raised the alarm.)
I wasn't sure—it had been a while since I'd had it checked. The next day I went to the lab for a quick blood panel, and sure enough, my vitamin D level was "three points away from precipitating calcium outside of [my] bones, which is not good."
I immediately started supplementing my vitamin D and zinc, made a few swaps to my haircare routine (it now incorporates a lot of apple cider vinegar, like a Bragg ACV Rinse and this buildup-balancing ACV shampoo by Acure), and my dandruff has mostly disappeared.
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Prior to that appointment, I knew vitamin D was important for healthy bones and overall immunity—but I had no idea it was so strongly linked to systemic skin concerns like psoriasis, eczema, dandruff, and inflammation. To be clear, vitamin D is certainly not a cure for any of these conditions—but if it helped my scalp, it might help yours, too.
To find out more about the connection between vitamin D and skin health, I spoke to two top dermatologists and a holistic nutritionist. If you're dealing with dandruff or a scaly scalp, here's how to determine if you should supplement with vitamin D.
What are the major types of scalp flaking—and what causes them?
There are two common conditions that account for the majority of flaky, scaly scalp concerns: dandruff (which is a form of eczema) and psoriasis (which is a chronic autoimmune condition).
1. Dandruff and seborrheic dermatitis
The first type is dandruff, a form of eczema that can advance into a more severe condition called seborrheic dermatitis. "This is the most common cause of a flaky scalp," says Corey Hartman, M.D., FAAD, a board-certified dermatologist and an assistant clinical professor of dermatology at the University of Alabama School of Medicine. "It is caused by a yeast that is present on everyone's scalp as part of the normal flora. The yeast, called Malassezia, feeds on the skin's sebum—which is why seborrheic dermatitis is most common on oil-rich areas of the body." He explains that Malassezia sets up an inflammatory reaction in the skin that results in flaking, redness, itching, and greasy patches.
Dr. Hartman also points out that darker-skinned individuals with curly hair are especially prone to seborrheic dermatitis since they're more likely to apply oil to the scalp to manage their hair (as opposed to those with straight hair, who typically wash excess oil away frequently). "I find that many patients with curly hair experience scaly scalp and then apply more oil in an attempt to control the problem—not realizing that they are making the problem worse by further feeding the yeast."
While we know that seborrheic dermatitis involves Malassezia and an irregular response of the immune system, the exact cause is still unclear—and it's believed that a range of other triggers can play a role. "It can sometimes be triggered by a change in temperature," says Eva Simmons-O'Brien, M.D., a board-certified dermatologist and assistant professor of internal medicine at the Johns Hopkins University School of Medicine—for example, in "the winter months, when it's colder outside and there's less humidity in the air." She says others might be more susceptible to dandruff or seborrheic dermatitis when they're under a lot of stress or have used a new hair product (like a hair spray or dye) that causes irritation or sensitivity.
How do you know if your flakes fall in the dandruff and/or seborrheic dermatitis department? "You'll see them—on your shoulders, on your sweater, even in your eyebrows or on your glasses," says Dr. Simmons O'Brien. "You might scratch a bit and feel them coming off. But you won't experience any discomfort from it."
And that takes us to the next condition—psoriasis—which is a lot more uncomfortable.
"Scalp psoriasis is a common inflammatory condition that causes itchy, scaly plaques on the scalp," says Dr. Hartman. "It's caused by an immune dysregulation in the skin that causes skin cells to be produced too quickly and build up into thick plaques." He says that psoriasis can affect the skin on any part of the body and can also affect the joints, which results in psoriatic arthritis. Symptoms of scalp psoriasis include scaly red patches, silvery-white sales, dandruff-like flaking, dry scalp, itching, burning, and hair loss.
In addition to causing those very challenging symptoms, psoriasis can also lead to further complications. "It's an inflammatory condition where the skin has a very difficult time hanging onto hydration, so there's a lot of transepidermal water loss," says Dr. Simmons-O'Brien. "The uppermost layer of the skin, called the stratum corneum, is basically at risk for being injured and invaded by bacteria and viruses in those areas of the psoriatic lesions." The telltale sign of psoriasis is the presence of those lesions—raised areas of skin that are often pink or red. (It's important to note, though, that if you are a person of color, the lesions may not be pink or red, but could actually match your skin tone, be hyperpigmented, or could take on a scaly, gray/taupe appearance.) "They may also feel very tender and sensitive, or they might itch and burn," says Dr. Simmons-O'Brien. "And they often bleed easily when using a brush or shampooing the area."
What is vitamin D, and how can it improve scalp health?
While vitamin D is most commonly associated with calcium and bone health, it's an extremely important vitamin that functions as a hormone and affects multiple organ systems throughout the body—including the skin—and has been shown to reduce inflammation and help control infections.
"It's been well established that inflammatory conditions of the skin, like eczema and psoriasis, are often associated with—and are made worse by—vitamin D deficiency," says Dr. Simmons-O'Brien. "If you have a flaky scalp, and particularly if you have psoriasis, taking vitamin D is going to help bolster the immune health of the scalp, decrease inflammation, help retain hydration, and help the skin fend off yeast or bacterial organisms." The way the vitamin D is administered matters, though—so you may need to talk to a doc to discuss whether topical treatments or supplements are right for you.
The skin benefits of vitamin D aren't limited to the scalp, of course: You'll likely be interested to know that vitamin D prevents skin aging and helps in skin cell growth, repair, and metabolism, too. One study showed that the use of oral vitamin D not only has great potential in clearing psoriatic skin lesions but also decreases the risk for cardiovascular disease and other disease morbidities.
Of course, if you're dealing with a scalp health issue, vitamin D isn't going to be a one-stop solution to your problems; instead, think of it as the first step to getting your overall skin health in better shape as you target the situation with other treatments. "While vitamin D will not cure seborrheic dermatitis or scalp psoriasis, it can help to strengthen the immune system, which would then indirectly affect the skin in a positive way," confirms Dr. Hartman.
Who should be taking a vitamin D supplement—and how much?
In a word? You. (But how much, exactly, will vary.) "It has been reported that as many as 41% of adults in the United States are deficient in vitamin D," says Dr. Hartman. (Some signs of deficiency include frequent illnesses and infections, fatigue, bone and back pain, depression, poor wound healing, bone loss, hair loss, and muscle pain.)
"Everyone should be taking a vitamin D supplement to ensure that levels are optimal, but especially those with darker skin or who eat a diet low in fish and dairy, use sunscreen frequently, rarely spend time outside, or are elderly or overweight," says Dr. Hartman. (You should find yourself on this list because you do wear SPF every single time you step outside...right? Right.)
As a baseline, the National Institutes of Health recommends 600 IU daily for women between the ages of 19 and 50. (If you're in another category, you can check out the full RDA chart here.) "However, for well-health optimization, most dermatologists suggest that individuals between the ages of 19 and 50 take a minimum of 1,000 to 2,000 IUs daily," says Dr. Simmons-O'Brien. (This is especially important if you know for sure that you're deficient in vitamin D or if you check off any boxes for risk factors. More on those later.)
Dr. Simmons-O'Brien, for example, often recommends 2,000 IU daily to her patients who are 12 and older. "That's to maintain a good value," she says. "If it's anything less than that, it's essentially just not enough, because the value drops very easily and it takes a while to get to where it needs to be."
So, the most accurate way to plan your perfect dosage is to work with a doctor to have your levels checked.
When and why should you check vitamin D levels with a blood test?
Okay, so nobody loves running to the doctor for a blood test, but hear me out: Getting your levels checked is the most surefire way to supplement appropriately and safely, and there are lots of good reasons for doing it.
"If you're experiencing a flaky scalp, I would recommend that you first get vitamin D levels checked to determine what's going on before running out and relying on any single course of treatment, like a dandruff shampoo," says Dr. Simmons-O'Brien. She recommends a "village approach" that utilizes multiple methods of prevention and treatment working in tandem together: supplementing with vitamin D to set a healthy internal foundation, using quality topical products to manage the yeast or bacteria overgrowth, and then possibly seeing a dermatologist for prescription treatment if needed.
It's especially important to get a blood test if you have risk factors or signs of vitamin D deficiency. Depending on your levels, your doctor may recommend a dosage beyond the standard supplementation protocol. (For example, I started with two weeks of a high-dose prescription vitamin D to get my levels up and then switched over to a daily maintenance dose.)
And on the other side, accidentally overcompensating with vitamin D can be dangerous. According to Harvard's T.H. Chan School of Public Health, vitamin D toxicity (which can cause weight loss, irregular heartbeat, and heart and kidney damage) most often occurs from taking supplements—which is why it's not recommended to take more than 4,000 IU daily unless monitored by a doctor. By knowing your true vitamin D level, you'll be able to supplement in the safest way possible.
Simply ask your primary care doc or dermatologist to run your levels. (And since you're getting blood drawn anyway, they'll likely recommend running a few other tests—like zinc levels—to get a better snapshot of your overall wellness.)
The standard acceptable range of vitamin D is between 30 to 100 ng/ml, but Dr. Simmons-O'Brien says it's best to aim for a minimum of 50 to 60 ng/ml to create a healthy cushion—partly because it's winter and levels are likely to be lower and partly because we're in a pandemic and your immune system will benefit greatly from sufficient vitamin D, which is important for staying healthy in general.
When's the best time to take a vitamin D supplement?
Dr. Hartman recommends taking your vitamin D supplement in the morning after a high-fat snack to enhance absorption (good news for all you fried-egg-over-avocado-toast fans). "Vitamin D is a fat-soluble vitamin, so it's dissolved best in your bloodstream when paired with high-fat foods," he says, adding that taking vitamin D at the same time every day is also recommended for both consistency and convenience.
"Another reason to take the supplement early in the day is that several studies have shown it may affect sleep," Dr. Hartman says. "High levels of vitamin D have been linked to lower levels of melatonin, the sleep hormone." (And because we believe in protecting beauty sleep at *all* costs, it's best not to mess with it.)
Additionally, Dr. Simmons-O'Brien recommends popping a probiotic along with your vitamin D. "Healthy gut flora enhance the absorption of vitamin D, so it's a good idea to also be taking a high-quality, multi-strain probiotic to get the most out of your vitamin D supplement." (Try Seed, a daily 24-strain, broad-spectrum probiotic and prebiotic.)
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Are there other ways to get vitamin D besides supplements?
You can get a limited amount of vitamin D through your diet: Dr. Simmons-O'Brien recommends fatty fish in particular (try salmon, swordfish, tuna, sardines, and cod liver oil). "Beef liver, eggs, and fortified dairy are also decent sources of vitamin D," says Jessica Waller, CNS, a holistic nutritionist. "If you're plant-based, mushrooms and fortified plant-based kinds of milk are your best bets. Look for a non-dairy milk that specifically states [it's] fortified with vitamin D3."
Just remember that diet alone is rarely (and, honestly, probably never) a sufficient way to get your daily value of vitamin D. Topical vitamin D treatment exists, too, in the form of calcipotriol—but it's available by prescription only, so Dr. Simmons-O'Brien suggests working with a doctor to determine if it's right for you.
And when it comes to getting vitamin D the old-fashioned way, from the sun? Pass, please. "It takes a significant amount of sun exposure to produce enough vitamin D to be useful, and this sun exposure comes with increased risk of skin cancer and premature skin aging," says Dr. Hartman. "We have too many other safe means of obtaining vitamin D that don't contribute to a risk of malignancy." Dr. Simmons-O'Brien also points out that for people with darker skin (those who have skin types three, four, five, and six on the Fitzpatrick scale), it's almost impossible to get sufficient vitamin D through sun exposure since the sun will bypass the layer of skin where vitamin D should be made.
"That's why people of color are often deficient in vitamin D. Those with darker skin types are not able to make it in their skin, so they never have adequate storage levels of vitamin D," she explains. "If you are light brown, medium brown, or darker complected, you'll definitely need to rely on supplementation in addition to diet."
What are the best vitamin D supplements?
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"The Thorne Vitamin D/K2 Liquid offers vitamin D suspended in medium-chain triglyceride (MCT) oil and combined with K2, which helps with absorption," says Waller. "Because vitamin D is a fat-soluble vitamin, it's more bioavailable when taken with an oil." She adds that vitamin K2 is also essential for vitamin D metabolism—and most of our K2 is made by gut bacteria. "If you have any microbiome issues, your K2 production may be decreased, so it's helpful to have a safety net."
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"The Designs for Health Liposomal Vitamin D Supreme supplement combines vitamin D with vitamins K1 and K2," says Dr. Hartman. "By combining vitamins K and D in liposomes (tiny fat spheres used as carriers for vitamin D), the synergy of the two vitamins enhance each other's effects to promote bone and heart health."
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Both dermatologists recommended the Pure Encapsulations brand, which offers hypoallergenic options free from eight common allergen categories. "For those severely deficient in vitamin D, I recommend Pure Encapsulations D3 250 McG (10,000 IU)," says Dr. Hartman. Remember: When supplementing in high doses for a deficiency, it's important that you work closely with a doctor to monitor your vitamin D levels.
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Looking for a supplement for a little one in your life? (The AAP recommends 400 IU of vitamin D daily for all breastfed babies under 1 year old, while some kids might benefit from continued use—so if your child has eczema, for example, talk to your pediatrician.) "Carlson Labs' Kid's Super Daily D3 + K2 is a great option for children who are vitamin D deficient," says Dr. Hartman. "It only contains D3, vitamin K2, and medium-chain triglycerides (MCTs) as the carrier oil, making it a healthier choice for a child than brands [that] add sugar."