Multiple SclerosisPatient friendly summary

  • Lower rates of MS are seen in areas that have more solar UVB radiation.
  • Lower levels of vitamin D are associated with a higher risk of MS.

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system. It affects the brain, optic nerve, and spinal cord.

Autoimmune diseases occur when the immune system attacks normal body tissues rather than foreign organisms. When the body’s own immune cells attack the nervous system, it causes inflammation. With MS, inflammation repeatedly damages the myelin sheath that covers and protects the body’s nerve fibers. This damage causes nerve impulses to slow or stop altogether. The symptoms of MS vary among individuals with the disorder.

Risk factors

Known risk factors for MS include:
  • Epstein-Barr virus infection: People with MS have higher levels of the Epstein-Barr virus antigens. This may be due to an overactive natural immune response that occurs when vitamin D levels are low, such as in winter.  
  • Cigarette smoking: Studies have shown a link between smoking and MS, particularly in those with high Epstein-Barr virus antigens.

Sunlight exposure and multiple sclerosis risk

Studies have shown that sunlight may limit the rates and severity of MS:
  • The disease occurs more frequently with increasing distance from the equator, where there is less solar ultraviolet-B (UVB) light.
  • More sun exposure throughout life is associated with a reduced risk of MS.
  • Fewer disease symptoms are reported in summer, when there is more sunlight.
  • MS occurs more frequently in spring, when vitamin D levels are lowest.

Vitamin D and multiple sclerosis

Vitamin D levels

Observational studies have found that lower levels of Vitamin D are linked to an increased risk of developing MS. 

How vitamin D works

It is not known how vitamin D reduces the risk or severity of MS. However, it is likely that vitamin D suppresses cytokines involved in inflammation. (Cytokines are small molecules that help cells communicate. As a result, vitamin D may lower inflammation.

In winter, vitamin D levels are low. When exposed to an Epstein-Barr viral infection, the body’s natural immune system may overreact. This may trigger development of the autoimmune disease MS.


There are studies showing that lower vitamin D levels are a risk factor for MS. A study from Australia found a 7% reduction in risk of developing MS for each 4 ng/mL (10 nmol/L) increase in vitamin D levels in the blood.

Based on studies of viral infections and vitamin D levels, vitamin D levels above 40 ng/mL (100 nmol/L) may provide protection against MS.


Based on trials with vitamin D supplements, there is limited evidence of reduced MS severity with a higher vitamin D intake.

Find out more...

Do you want to find out more and see the research upon which this summary is based?  Read our detailed evidence summary on multiple sclerosis.

Page last edited: 17 May 2011