Earlier this year a study was published that verified, for the first time, an upper, safe limit for vitamin D, but what if, like many in the northern hemisphere, you are deficient in this hormone-like vitamin? Could a vitamin D deficiency be a trigger for your psoriasis? Several studies published in the last year make the connection between a vitamin D deficiency and psoriasis severity so should you be supplementing, sunbathing, or is there a reason to avoid vitamin D for naturally healthy skin?

In this extended post we will be taking a look at:

• Optimal vitamin D levels
• The prevalence of vitamin D deficiency across the world
• Who is at risk of vitamin D deficiency
• How vitamin D might affect the skin
• Can vitamin D supplements help reduce psoriasis symptoms?
• The different vitamin D supplements available
• Should you take vitamin D for psoriasis?

Optimal Vitamin D Levels

The recent study looked at more than a million adults over the age of 45 and analysed data to determine the optimal range for vitamin D levels in the blood as regards risk of cardiovascular events and overall mortality. What they found was that a serum calcidiol level of 20 to 36 ng/mL, offered the most significant risk reduction for serious cardiovascular disease and death during the 54 month study period.

This works out to around 50nmol/l to 90nmol/l when testing for calcidiol (25 hydroxyvitamin D). Unfortunately, few people are ever tested for vitamin D levels and so can be deficient for many years with adverse effects on bone health, the immune system and the health of the skin.

The Prevalence of Vitamin D Deficiency

Anyone living at 52°N is unlikely to get sufficient UVB exposure from October to April for optimal vitamin D synthesis, and those at 42°N get little UVB exposure from November to February. At 32°N or closer to the Equator there is enough UVB radiation year round to meet most people’s need for vitamin D synthesis on the skin.

A study looking at patients’ vitamin D levels in 11 European countries found that 36% of elderly male and 47% of elderly female subjects had a deficiency of the vitamin (van der Wielen et al., 1995). In a study carried out in Boston, researchers found that 73% of elderly black subjects were vitamin D insufficient, compared with 35% of elderly non-Hispanic whites (Harris et al., 2000).

Vitamin D synthesis declines with age but it is not only the elderly who are at risk of low vitamin D levels; another Boston-based study found that by the end of winter nearly two thirds of healthy, young adults had insufficient vitamin D levels (Tangpricha et al., 2002).

Vitamin D Deficiency – Who’s at Risk

Those at the highest risk for vitamin D deficiency include people who do not get regular exposure to sunlight, either because of the climate where they live or due to a lifestyle that involves spending most of their time indoors.

As such, the elderly, along with other adults and children in institutions such as nursing homes are at risk, as are those convalescing from an illness in hospital. Dark-skinned people are also at a higher risk as the synthesis of vitamin D on the skin is less significant when the skin’s pigment, melanin, blocks absorption of ultraviolet B rays.

Anyone with a gastrointestinal issue such as Crohn’s disease, Celiac sprue, short bowel syndrome or cystic fibrosis is also at a higher risk of becoming vitamin D deficient because of impaired absorption of the vitamin, even when supplementing.

Some medications also raise the rate at which vitamin D is broken down and excreted from the body, including Dilantin, phenobarbital, and rifampin (all of which increase activity of liver enzymes p450). Drugs which block cholesterol production (such as statins) may also predispose a person to a deficiency of vitamin D as 7-dehydrocholesterol is the substrate from which the active vitamin form is created.

Vitamin D Deficiency and the Skin

The effect of low vitamin D levels on the skin is not yet thoroughly understood. It may, however, be hypothesised that impaired absorption of calcium caused by low vitamin D levels will adversely affect the structure of the skin as calcium is essential for healthy cell development and the protective barrier of the skin.

Higher vitamin D levels are also connected to inhibited production of tumor necrosis factor-alpha (TNF-α), which is thought to be a factor in the occurrence and persistence of the lesions seen in psoriasis. TNF-α is an inflammatory agent the production of which is, ironically, stimulated by exposure to UVB.

Those looking to boost their skin’s production of vitamin D through sunbathing may see little difference then, or even a worsening of their psoriasis symptoms. Taking a vitamin D supplement would, perhaps, be preferable, especially as this also reduces the risks of skin cancer that increase with sun exposure.

Calcitriol itself, the active form of vitamin D, has been seen to inhibit cell proliferation but encourage cell differentiation, having a beneficial effect on two of the mechanisms associated with the development of psoriatic lesions. Keratinocytes, those cells responsible for the skin plaques familiar to psoriasis sufferers, may be a target for treatment using vitamin D supplementation it seems, especially as the vitamin also exerts an immunoregulatory effect.

This effect is due to calcitriol’s influence on T-cell activation and both antigen-presenting cells and dendritic cells; in effect, vitamin D helps the body to recognise its own cells so as not to attack them, as well as helping maintain a robust response to foreign invaders.

Using Vitamin D to Treat Psoriasis

Using vitamin D analogues, such as calcipotriene, 1,24-dihydroxyvitamin D3 and 1,25(OH)2D3, to treat psoriasis is not a new concept and these have been found to be as effective as strong topical corticosteroid creams (Fogh et al., 1994). These supplements are also well tolerated when used for psoriasis treatment over the longer term.

There has been an increase in the use of combination therapy for psoriasis involving a topical steroid plus a vitamin D analogue in recent years and such prescriptions appear to make up around 10% of treatments in the US (Davis and Feldman, 2013).

Many topical and oral treatments for psoriasis have adverse effects, especially when taken long-term, making combination therapies an attractive option for patients. These combination therapies are now more likely to work by affecting the hyperproliferation of keratinocytes that is the result of T-cell mediated autoimmune activity. Vitamin D application appears to be a therapy that works via such a mechanism (Raut et al., 2013).

A study published earlier this month found that those with atopic dermatitis were able to achieve improvements in their vitamin D levels through supplementation over a three week period (Hata et al., 2013). However, there was no observable change in symptom severity during that time. Longer studies are obviously needed to really assess the effects of improved vitamin D status. A recent Cochrane review (Mason et al., 2013) noted the following observations from a raft of clinical studies:

• Dithranol (vitamin D combined with a corticosteroid), and tazarotene work better for psoriasis than placebo.
• For body and scalp psoriasis, vitamin D and corticosteroid combined fared better than either alone.
• Vitamin D generally outperformed coal tar for psoriasis.
• Potent corticosteroids outperformed vitamin D when applied to scalp psoriasis.
• Topical potent corticosteroids were less likely to cause adverse effects (such as irritation and burning) than topical vitamin D.
• Combined corticosteroid and vitamin D therapy was better tolerated than vitamin D alone but as well tolerated as potent corticosteroids.

The authors of this latest Cochrane review recognise, however, that the long-term risks of skin dermal atrophy with prolonged treatment of chronic plaque psoriasis with corticosteroids remain unknown.

Other research has found that the stimulation by TNF-α of inflammatory interleukin 1-alpha in human keratinocytes taken from those with psoriasis is suppressed by both vitamin D and vitamin A (retinoic acid) (Balata et al., 2013) offering yet another possibility for combination therapy for psoriasis using nutraceuticals.

Vitamin D and Rosacea

Despite all of these studies finding promise in the use of vitamin D for psoriasis therapy, a study published this month found that patients with rosacea actually tended to have higher levels of vitamin D in their system than controls free of the skin disease (Ekiz et al., 2013).

These results need to be looked at carefully, however, as more patients with rosacea had a deficiency of vitamin D even though average levels were higher. In addition, none of the participants had particularly high levels of vitamin D, with the average for patients vs. controls being 21.4 ± 9.9 and 17.1 ± 7.9 ng/ml, respectively (putting almost all of them below the recommended level for serum calcidiol).

The prevalence of vitamin D deficiency in patients with rosacea was 38.6% and 28.1% in healthy controls, which all amounts to there being no clear positive correlation of skin health with vitamin D status and a necessity for more research to improve our understanding of these connections.

Which Vitamin D Supplement is Best – Vegan or Animal-Derived?

Supplements of vitamin D come in either D2 form (ergocalciferol) or as D3, also known as cholecalciferol. D2 is usually sourced from irradiated fungi, such as yeast, and is the vegan-friendly form of the supplement. Most D3 is animal-derived, usually from fish or from lanolin (sheep fat).

Non-animal sourced D3 is, however, also available now courtesy of a process where rice bran and mushrooms are exposed to UVB light. These forms used to be thought inferior to vitamin D3 from animal sources but the research now supports the idea of equipotency between D2 and D3 in terms of building blood calcidiol to optimal levels when taken at a dose of 1000IU per day (25mcg) (Holick et al., 2008).

This was confirmed again recently by Urbain, et al (2011), in a placebo-controlled trial which saw patients’ vitamin D levels rise after just two weeks of daily supplementation with vitamin D2 from button mushrooms exposed to UVB to convert the ergosterol on their surface to ergocalciferol.

Conclusions

The most sensible approach to treating psoriasis with vitamin D appears to be to ensure a regular, but not excessive, supply of the vitamin through supplementation, fortified foods and/or sun exposure (in moderation to ameliorate skin cancer risks).

Patients may also wish to talk to their physician about the use of topical vitamin D treatment, making sure to let them know if an oral supplement is already being used so as to prevent hypercalcemia. More controlled trials are clearly needed to fully elucidate the risks and benefits of vitamin D for psoriasis.

Further reading:

What is psoriasis?
Psoriasis symptoms and diagnosis.
Guttate psoriasis