Vitamin D

Vitamin D supplements are potentially important for people with RA for two reasons. Vitamin D plays an important role in maintaining adequate calcium levels in the blood and in absorption of calcium. Vitamin D is recognized as important in maintaining bone health and people with RA are at significantly increased risk for osteoporosis and bone loss due to RA disease processes and glucocorticoid use.¹

Vitamin D also plays an important role in immune system function. Abnormalities in the way cells use vitamin D have been linked to various autoimmune diseases. Results from a limited number of studies, indicate that vitamin D supplementation may provide some benefits in RA, including controlling disease activity and improvement of symptoms.¹

Vitamin D and risk for developing RA

Does vitamin D play a role in preventing RA? Results from animal studies have shown that vitamin D supplementation can forestall the development of autoimmune diseases like RA. However, results from studies in humans have been mixed. A recent broad review of studies examining the role of vitamin D and risk for developing autoimmune diseases did point to a potential role for vitamin D, especially in RA.²

Evidence from the Iowa Women’s Health study has lent strong support to the notion that vitamin D plays a key role in RA prevention. The study followed approximately 30,000 women who did not have RA for 11 years and found that those who a low vitamin D intake (less than 200 international units [IU] per day) were 33% more likely to develop RA than those with a higher daily intake of vitamin D.³

Role of vitamin D supplementation in RA treatment

There have been a limited number of studies examining the role of vitamin D supplementation in the treatment of RA. However, there is some evidence that vitamin D may provide benefits in patients with RA who are stabilized on disease-modifying anti-rheumatic drug (DMARD) therapy. In a randomized, controlled trial, patients receiving DMARD treatment who also received vitamin D (50,000 IU per week) had a somewhat greater (but not significantly greater) improvement in Disease Activity Score (DAS28) compared with those who received placebo. Side effects from high doses of vitamin D were generally mild.⁴

Checking your vitamin D level

Your doctor can check your vitamin D level with a simple blood test called 25 hydroxyvitamin D (250HD, for short). This test measures vitamin D levels in blood as either nanograms per milliliter (ng/mL) or in IUs (nanomoles per liter [nmol/L]), with 1 ng/mL equal to 2.496 nmol/L or IUs.  While there is no formal definition for vitamin D deficiency, there are some values that are generally used as a guide for what normal and deficient mean. ¹

• Normal: 250HD level higher than 30 ng/mL (75 nmol/L)
• Insufficient: 250HD level between 20 and 30 ng/mL (50-75 nmol/L)
• Deficiency: 250HD level less than 20 ng/mL (50 nmol/L)
• Toxic: 250HD level greater than 150 ng/mL (375 nmol/L)

Vitamin D sources and supplements

Dietary sources for vitamin D include fish, eggs, fortified milk, and fish oil (cod liver oil). Vitamin D is also produced by the body during exposure to the sunlight. Sun exposure for as little as 10 minutes may be sufficient to prevent deficiencies of vitamin D. There are two important forms of vitamin D in humans: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). For supplements, vitamin D3 is the recommended rather than vitamin D2 because the former is the naturally occurring form of the vitamin and may be more effective at raising blood levels.¹

Vitamin D is contained in most multivitamins in doses from 50 IU to 1,000 IU and is available alone in tablets, capsules, and liquids. There is some debate about how much vitamin D is sufficient. Keep in mind that the safe upper limit for daily vitamin D intake is 10,000 IU. The goal of vitamin D3 supplementation is to achieve a 250HD level in the rang eof 30 to 60 ng/mL for optimal bone health. The optimal vitamin D3 250HD range for immune system effects is less clear. If you would like to use vitamin D supplements, talk to your doctor first. This is especially important with vitamin D, because taking too much of this vitamin can pose a danger to your health. Your doctor can give you a blood test to find out your blood level of vitamin D and, if it’s below normal, your doctor may suggest a daily supplement amount to bring your levels up to normal.¹