What Is a Healthy Vitamin D Level?
Most adults should have a blood vitamin D level of at least 50 nanomoles per liter (nmol/L), according to the Office of Dietary Supplements. Being below 30 nmol/L can have negative health effects, including weakened bones, and being above 125 nmol/L can also cause health problems, per the Office of Dietary Supplements.
According to preliminary results of a study presented at the annual meeting of the American Society for Nutrition, of 491 people with psoriasis, those with the lowest vitamin D levels had the largest proportion of their bodies impacted by the itchy, scaly patches (called plaques) that are a hallmark of this inflammatory skin disease.
In the study, people with the fewest signs of psoriasis on their skin had average vitamin D levels of 67 nmol/L, compared with 56 nmol/L for participants with the most evidence of psoriasis on their skin. In addition, only 25 percent of people with the lowest amount of plaques were vitamin D deficient, versus 39 percent of the people with the highest number of plaques.
These results suggest that upping vitamin D levels would benefit people with psoriasis. But it’s not clear what those levels should be or what the best way is to achieve such levels.
“Maintaining vitamin D levels at a slightly higher threshold than typically recommended for the general population might be beneficial for individuals with psoriasis,” says Danilo Del Campo, MD, a dermatologist at Chicago Skin Clinic in Illinois. “However, the evidence to confirm this is not yet robust, and more studies are needed.”
Sources of Vitamin D
Vitamin D is primarily obtained through sun exposure — the body makes vitamin D when skin absorbs UV rays. It’s also naturally available in a few foods like fatty fish (trout, salmon, tuna, and mackerel) and in smaller amounts in beef liver, egg yolks, and cheese. A number of foods, including milk, breakfast cereals, and orange juice, are fortified with the vitamin.
Because of the risk of skin cancer with increased sun exposure, the American Academy of Dermatology (AAD) doesn’t encourage more time outside to boost vitamin D levels. It can be difficult to get the recommended amount of vitamin D from your diet alone, which is why supplements may be beneficial.
Vitamin D2 vs. Vitamin D3
Vitamin D is available in two forms: plant-derived vitamin D2 or vitamin D3 from animal-based foods (D3 is also produced when skin is exposed to sunlight). Supplements and fortified foods contain both vitamin D3 and vitamin D2.
For vitamin D to be used by the body, it has to be converted, or hydroxylated, first by the liver and then by a process involving the kidneys. Research has found that vitamin D3 is better absorbed by the body, and a meta-analysis of 20 studies found that vitamin D3 is better at raising vitamin D serum levels. According to the Office of Dietary Supplements, D3 might raise blood levels of vitamin D higher and for longer than D2.
Topical Vitamin D for Psoriasis
Topical vitamin D has long been among the treatments for psoriasis, often in combination with topical corticosteroids, according to the AAD.
“Topical treatments for psoriasis often contain synthetic forms of vitamin D,” says Dr. Del Campo. “These compounds are adept at regulating the skin cell growth cycle, slowing the overproduction of skin cells and reducing the inflammation and scaling characteristic of psoriasis.”
That’s because vitamin D helps regulate the immune system, and when levels are low, an overactive immune response may lead to rapid skin cell turnover, a defining feature of psoriasis, Del Campo says. Reduced sun exposure because of physical discomfort or concerns about how psoriasis looks can also contribute to lower vitamin D levels, Del Campo adds.
Topical vitamin D analogues (synthetic vitamin D) are very safe, adds Faranak Kamangar, MD, chair of dermatology at the Palo Alto Medical Foundation, which is part of Sutter Health in California. However, topical treatments don’t alter vitamin D levels in the body.
Phototherapy and Vitamin D
Another common treatment for psoriasis is phototherapy, which involves routinely exposing the skin to an artificial UVB light source for a set length of time. Studies have shown that narrowband UVB (NB-UVB) exposure increases vitamin D levels and decreases disease severity in people with psoriasis.
Researchers have also looked into the role that vitamin D plays in the gut microbiota and gut health (a healthy gut has many implications for overall health). One study showed that deficient levels of vitamin D negatively impacted gut microbiome diversity, and exposure to NB-UVB light increased gut microbiome diversity in individuals who were vitamin D deficient.
Should Everyone With Psoriasis Take a Vitamin D Supplement?
Deirdre Hooper, MD, cofounder of Audubon Dermatology in New Orleans, recommends that everyone with psoriasis take a daily 600 milligram vitamin D supplement.
“It definitely makes sense for psoriasis patients to check their vitamin D levels, and if low, definitely supplement,” says Dr. Kamangar. But if lab levels are normal, it’s unclear how much vitamin D supplements will help, she adds.
A meta-analysis of studies evaluated whether oral vitamin D supplementation improved the Psoriasis Area and Severity Index (PASI) and found no significant differences in PASI after 3, 6, and 12 months of supplementation. Researchers note that other factors are likely involved in the absorption of vitamin D, and more studies are needed to determine how effective vitamin D supplementation is in those affected by psoriasis, including what the optimal dosage might be and potential combinations of supplements.
While low levels of vitamin D are associated with psoriasis, it is also possible to get too much vitamin D, which can cause high blood calcium levels and raise the risk of heart disease. It’s always a good idea to check with your doctor before starting on any supplements.
