Ankylosing spondylitis Patient friendly summary

  • There is no evidence that sunlight or vitamin D lower ankylosing spondylitis risk.
  • Vitamin D may benefit people with ankylosing spondylitis. It reduces inflammation and improves bone mineral density.

Ankylosing spondylitis (AS) is a lifelong autoimmune disease. The immune system begins attacking healthy cells.

Ankylosing spondylitis is also a form of arthritis.

Symptoms include inflammation, pain, and stiffness (mainly in the spinal joints).

Risk factors

The risk factors for ankylosing spondylitis appear to be:

  • Genetics
  • Environmental (bacterial infections)        

Sunlight exposure and ankylosing spondylitis risk

There is no evidence that sunlight lowers ankylosing spondylitis risk.

Vitamin D and ankylosing spondylitis

Vitamin D levels

Few studies have researched the effects of vitamin D on ankylosing spondylitis. However, there have been reports that people with ankylosing spondylitis have low bone mineral density. In addition:

  • In a 2001 study, alterations in vitamin D metabolism may contribute to low bone mineral density.
  • In Austria, people with ankylosing spondylitis also had inflammation that may affect bone mass density.

How vitamin D works

For those with ankylosing spondylitis, inflammation appears to be a risk factor for low bone mineral density. Vitamin D reduces the production of inflammatory compounds that are part of the immune system. Higher vitamin D blood levels increase calcium absorption from the diet. Thus, there are two ways vitamin D may increase bone mineral density for those with ankylosing spondylitis.


There is no evidence that vitamin D can reduce the risk of ankylosing spondylitis.


Vitamin D can improve bone mineral density and reduce inflammation associated with ankylosing spondylitis.

There are no reported guidelines for using vitamin D to treat ankylosing spondylitis. Results for other diseases, including osteoporosis, indicate that raising vitamin D levels to 30–40 ng/ml (75–100 nmol/L) may be beneficial.

Find out more...

We will be adding a detailed evidence summary on this topic in the near future.  Please check back soon to find out more.

Page last edited: 17 May 2011