Vitamin D and Psoriatic Arthritis: What’s the Link?

The trademark symptoms of psoriatic arthritis (PsA) include patches of irritated, scaly, and flaky skin on the elbows, knees, and across the trunk of the body. These symptoms can be uncomfortable all year round.

However, there is often a noticeable worsening of symptoms, or “flare-ups,” during the winter months.^1,2 Days are shorter, and the weather tends to be cooler in the winter. This also means that there is less exposure to natural sunlight, a primary source of vitamin D. Could there be a connection between the reduced amount of vitamin D and the increase of psoriatic arthritis flares?

Vitamin D deficiency

The body needs vitamin D to help with calcium absorption and bone growth. Vitamin D also helps manage the body’s immune and neuromuscular systems. Vitamin D can also play a role in cell growth.³ Not having enough vitamin D in the body is known as vitamin D deficiency. Vitamin D deficiency is linked to many health problems, such as:³

• Type 1 diabetes
• Multiple sclerosis
• Lupus
• Rheumatoid arthritis
• Thyroid disorder
• Cancer
• Parkinson’s disease
• Alzheimer’s disease
• Mental illness

Vitamin D deficiency and psoriatic arthritis

We know that PsA flares have been linked to the winter season. And reduced exposure to natural sunlight can contribute to vitamin D deficiency. Now doctors have begun to explore if there is a connection between vitamin D deficiency and the rise in wintertime psoriatic arthritis flare-ups.

One recent study found that most people with PsA are also vitamin D deficient. Despite this observed connection, doctors were not able to prove that the vitamin D deficiency was the cause of PsA or its related symptoms. Still, doctors note that even though vitamin D deficiency is not the cause of PsA, it does keep the body from doing its job of keeping skin healthy. And, not enough sunlight exposure is a common trigger for the symptoms of PsA.^1,2

How can I prevent vitamin D deficiency?

Since vitamin D deficiency seems to contribute to psoriatic arthritis, it is important to know your level. Finding out if you are vitamin D deficient is easy. All that is needed is a blood test. Healthy vitamin D levels are at or above 20 nanograms per milliliter (ng/ml). The optimal minimum vitamin D level for health is 30 ng/ml or higher. Be sure to talk to your doctor to see what amount is right for you.²

Vitamin D supplements

If your blood vitamin D level is too low, you can add a vitamin D supplement taken by mouth to your diet. Typical doses of vitamin D supplements are between 400 and 1,000 international units (IU) per day. You can also eat foods rich in vitamin D such as oily fish like salmon, halibut, or cod, eggs, shellfish, or dairy products with added vitamin D.⁴

Vitamin D creams for psoriatic plaques

There are also vitamin D creams that can be applied directly to skin plaques. These creams will not raise your vitamin D blood levels, but they can help reduce the plaques.²

Sunlight

While humans clearly need vitamin D for health, most of the body’s vitamin D comes from exposure to sunlight, not foods and pills. Regular, natural sunlight exposure is an excellent way to fight vitamin D deficiency, and it is free.

However, too much sunlight can also have health risks. That is why experts suggest starting out with 5 minutes of direct sun exposure with no sunscreen before 11 a.m. if you are very pale and likely to burn. You can spend more time outdoors in the sun if you have darker skin, or wear sun protection.⁵