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Laurance Johnston, Ph.D.

Periodically, I've discussed how sunshine and sunshine-generated vitamin D are good for individuals with spinal cord injury and dysfunction (SCI/D). For example, previously I reviewed how the lack of sun exposure and the vitamin-D deficiency that may ensue is associated with multiple sclerosis (MS). This update revisits the issue, highlighting studies that have emerged since then supporting this association.

Sunshine & Vitamin D

In brief review, skin synthesizes vitamin D when exposed to the ultraviolet-B (UVB) component of sunshine.  UVB exposure can vary greatly depending upon many factors, including time of day (more midday), season (more in summer), latitude (more near the equator), altitude (more in the mountains), weather conditions, and sunscreen use.

In the case of latitude and season, if you live north of about 37 degrees (roughly, a line from Richmond to San Francisco), you will have little vitamin-D production during winter months because the sunís zenith angle is so low that the atmosphere absorbs most UVB rays before they can reach you. In my case, because I live in sun-drenched Albuquerque, New Mexico (35 degrees) at 6,000-feet elevation, I will have at least some UVB exposure throughout the year.

Because it is fat soluble, excess, sun-produced vitamin D is stored in body fat and can be later used in sun-deficient periods. 

It should be emphasized that sun exposure, not food, is our primary natural source of vitamin D.  With the exception of oily fish foods, (e.g., salmon, sardines, mackerel, and cod liver oil), relatively few foods naturally contain much vitamin D. Although numerous other foods, like milk, have been vitamin-D fortified, their consumption is generally not enough to generate health-optimizing vitamin-D levels.

Overall, we have become a vitamin-D-deficient society because most of us work indoors and have been indoctrinated to avoid sun exposure. Unfortunately, the lack of this nutrient is implicated in the development of numerous disorders, including osteoporosis, cancer, cardiovascular disease, diabetes, and, the focus of this article, multiple sclerosis..

Immune-System Influence

Scientists have shown that vitamin D plays a critical role in maintaining an effective immune system. Virtually any disorder involving the immune system will be influenced by the lack of this crucial vitamin. This appears to be the case for MS, an autoimmune disease that causes the body to attack its own central nervous system (CNS). 


Although MS is influenced by multiple interacting genetic, environmental, nutritional, hormonal, immunological, and viral factors, its prevalence is strongly correlated with exposure to UVB-containing sunlight capable of producing vitamin D and, in turn, the factors affecting such exposure.

Overall, MS incidence increases the farther you live away from the equator; e.g., there is more MS in the northern than southern US.  Growing up in the north increases your odds of acquiring MS as an adult, but even as an adult your risk can be lowered by moving south (e.g., from overcast Seattle to sunny Phoenix).

In an example involving elevation, Swiss who live at lower altitudes have more MS than those who live further up in the mountains with greater exposure to vitamin-D-producing UVB radiation.

In a nutritional example, Norwegians who live near the ocean and, as a consequence, eat more vitamin-D-rich seafood have a lower MS risk than those who live inland, even though both groups lack sufficient sunlight to generate vitamin D through much of the year.

All these correlations strongly suggest that vitamin-D deficiency is a key factor in MS development and expression.

Sample Studies

Recent studies supporting the vitamin D-MS link include the following:

     Studying 95,000 women, Harvard University scientists concluded that vitamin-D intake was associated with a substantially reduced risk of developing MS (2004).

     Using the Department of Defenseís Serum Repository of over seven-million individuals, Harvard investigators determined that military personnel with higher vitamin-D levels were less likely to acquire MS (2006).

     A 2013 Iranian study showed that MS severity is correlated with vitamin-D levels. Patients with lower vitamin-D levels tended to have severe relapsing-remitting MS as opposed to the milder relapsing-remitting form of MS, and were more disabled.

     Finnish investigators demonstrated that high dose vitamin D resulted in fewer brain lesions, less disability, and better walking (2012).

     A French study (2012) showed that monthly high-dose vitamin D resulted in a reduction in relapse rates. Those patients who obtained the highest levels of vitamin D in their blood had a 75% reduction in relapse rates.

     Swedish scientists determined that people with the highest vitamin-D levels were 61% less likely to develop MS than people with low levels (2012).

     Following up on observations indicating that the risk of developing MS peaks in people born during May (i.e., gestation over the winter) and decreases in those born in November (i.e., gestation over the summer), English investigators showed that MS-inclined May newborns not only had lower vitamin-D levels but also a greater number of autoreactive immune cells, i.e., the type which can turn on the body (2013).


Clearly, studies suggest that vitamin-D deficiency is associated with an increased risk of developing MS or expressing MS symptoms. As such, if you are concerned about MS, evaluate your vitamin-D levels (a simple test), and if low, take a vitamin-D supplement or get more sun exposure.  Itís a no-brainer; the odds are it will help you one way or another.

Adapted from article appearing in December 2013 Paraplegia News (For subscriptions, call 602-224-0500) or go to