Q. I keep reading about the use of vitamin D with autoimmune diseases. How important is it for Sjögren’s patients?
A. Vitamin D is important in bone and cartilage homeostasis. New evidence indicates that vitamin D may have extraskeletal benefits on several systems including the immune system. Autoimmune diseases such as systemic lupus (SLE), and Sjögren’s have been associated in a few studies with low vitamin D levels. However, the significance of low vitamin D levels in disease pathogenesis and prevention is unclear.
What are the sources of vitamin D? Vitamin D has two precursors, Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D3 is synthesized mainly in the skin by the action of ultraviolet light. Vitamins D2 and D3 are found in very few dietary sources, such as fish oils or fortified dairy products, as well as supplements.
Recommendations regarding desirable levels are based upon evidence related to bone health. Some controversy exists, but experts such as the International Osteoporosis Foundation suggest that a minimum level of 30 ng/mL is necessary to decrease the risk of falls and fracture.
Vitamin D deficiency is very prevalent in the general population and some studies indicate a higher prevalence of vitamin D deficiency in certain autoimmune diseases. However, these studies have not been conclusive. As an example, in SLE patients, recent studies have indicated the prevalence of vitamin D deficiency to range between 38% and 96%. The wide variation can be attributed to many factors, such as the age of the patients recruited, geographic location, season at the time of the study, ethnicity, medications used and the accuracy of the vitamin D assay method used.
In Sjögren’s, few small trials have been performed to assess the prevalence of low vitamin D levels and the association with disease severity. No conclusive data has been assembled to indicate that subjects with Sjögren’s have lower vitamin D levels than healthy subjects, or to suggest a pathogenic relationship between lack of vitamin D and development of disease.
Patients with Sjögren’s can be prone to vitamin D deficiency. Photosensitivity, where exposure to ultraviolet light triggers a rash is prevented by avoiding exposure to sunlight, could contribute to lower levels of vitamin D. Furthermore, certain medications may aggravate vitamin D deficiency. Chronic corticosteroid and hydroxychloroquine use are suspected to affect vitamin D concentration and activity respectively.
In summary, although there are no guidelines regarding optimal vitamin D levels for extraskeletal and immune system health, it would be reasonable to recommend that patients be screened for vitamin D deficiency and treated with supplementation. The American College of Rheumatology recommends a daily intake of 800–1000 IU per day of vitamin D in patients on treatment with steroids.
by Stamatina Danielides, MD
This information was first printed in the The Moisture Seeker, SSF's patient newsletter for members.