As we’re reported in recent months, research results continue to underscore the importance of vitamin D: a once-overlooked nutrient, among whose very few good food sources sockeye salmon ranks number one.
Fortunately, humans are hard-wired to generate ample amounts of vitamin D when UV sunrays strike their skin. Unsurprisingly, people in northern temperate zones display vitamin D levels that range from sub-optimal to decidedly deficient.
These shortages, which stem from poor sun exposure, aren’t severe enough to produce overt symptoms like rickets, but appear to raise the risks of bone fractures and several common cancers (see “Vitamin D vs. Cancer” and “Vitamin D and Cancer: A Sunny Follow-Up Story”).
And a Harvard study published late last year supports the conclusions of a 2004 Harvard investigation: the first to reveal a connection between multiple sclerosis (MS) and low body levels of vitamin D.
In the 2004 study, researchers led by Harvard's Kassandra Munger used data from two large epidemiological studies conducted in women: the Nurses' Health Study (92,253 women) and Nurses' Health Study II (95,310 women).
This earlier analysis showed that the risk of MS was 33 percent lower among the women whose total vitamin D intake ranked in the highest fifth (quintile), compared with those in the lowest fifth.
And the authors also found that the risk of MS was 41 percent lower among women who took 400 IU or more of supplemental per day, compared with women who reported taking no supplemental vitamin D. No association was found between vitamin D from food and MS incidence, probably because the average American diet contains so little.
Multiple sclerosis (MS) afflicts some 350,000 people in the United States, making it among the most common neurological diseases in young adults. Worldwide, MS affects 2 million people.
Significantly, rates of MS are higher in northern regions of the globe and lower in sunnier tropical climes.
Here’s the scoop on the new Harvard study, followed by our report on some related research in lupus and fibromyalgia.
Studies suggest vitamin D deficiency may play a role in MS
As we've noted, MS is more common in northern latitudes. In addition, vitamin D prevents MS from developing in
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Harvard-based authors Kassandra Munger and Dr. Alberto Ascherio
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animals.
And two years ago, Finnish researchers reported intriguing findings that received little attention (Soilu-Hanninen M et al 2005):
- MS patients had lower tissue levels of vitamin D from June to September, compared with healthy controls. (Levels were the same in both groups during winter months.)
- MS patients’ vitamin D stores were higher when their symptoms were in remission.
Last month, another team led by Harvard's Kassandra Munger published the results of a study that seems to strengthen the connections between vitamin D and MS (Munger KL et al 2006).
Drawing on samples stored by the US Department of Defense, they examined blood from 257 military personnel diagnosed with MS and 518 healthy controls, and divided the samples into five categories (quintiles), based on the amounts of vitamin D in the blood (nanomoles per liter or nmol/L).
The Harvard-led team found that the risk of MS among non-Hispanic Caucasians decreased as blood levels of vitamin rose. Specifically, every 50-nmol/L increase in vitamin D (25-hydroxyvitamin D) cut the risk of MS by 41 percent.
And the people whose blood showed the highest levels of vitamin D enjoyed a 62 percent lower risk of developing MS.
Further, the inverse correlation between high vitamin D levels and risk of multiple sclerosis was particularly strong among personnel whose blood was drawn before the age of 20, suggesting that having high levels in early adulthood may be particularly protective.
The relationship between vitamin D and MS was weaker among blacks and Hispanics. However, the researchers noted that the smaller numbers of these individuals and their very low levels of vitamin D (due to having more UV-blocking pigment in their skin) may have made a relationship between vitamin D and MS harder to detect.
It is important to note that this study does not prove a cause-effect relationship, although the researchers could propose no other plausible explanation.
While the authors noted some unlikely possibilities, they came to the only logical conclusion: “The results of our study suggest that high circulating levels of vitamin D are associated with a lower risk of multiple sclerosis.” (Munger KL et al 2006)
Vitamin D in lupus and fibromyalgia
In addition to MS, there may be links between low body levels of vitamin D and these two conditions.
Let's take a look at two recent investigations.
Lupus study yields positive results
Systemic lupus erythematosus, better known as lupus, is an autoimmune condition that mostly afflicts women.
Researchers at the Medical University of South Carolina in Charleston knew that evidence from animal and clinical studies suggest that vitamin D inadequacies plays a factor in other autoimmune diseases (rheumatoid arthritis, multiple sclerosis, and type-1 diabetes), but this possible connection had never been well-studied in lupus.
After comparing vitamin D levels in 123 people with lupus and 240 healthy controls they detected a statistically significant in trend toward lower vitamin D levels in Caucasian lupus patients.
Specifically, 67 percent of the lupus patients were vitamin D deficient, with African Americans showing about half as much (15.9 ng/ml) compared to Caucasians (31.3 ng/ml).
As the Carolina team said (Kamen DL et al 2005), “These results suggest vitamin D deficiency as a possible risk factor for SLE [lupus] ...”.
Muscle pain linked to low vitamin D levels
Three years ago, researchers at the University of Minnesota Medical School in Minneapolis set out to measure the prevalence of vitamin D deficiency in patients with “… persistent, nonspecific musculoskeletal pain syndromes refractory to standard therapies” (Plotnikoff GA, Quigley JM 2003).
This is a set of symptoms many physicians might diagnose as "fibromyalgia". This term simply means "pain in muscles and fibers", and it refers to a mysterious condition characterized by patterns of pain in the muscles and fascia (connective tissue bands) of the back, often accompanied by fatigue. Fibromyalgia has no certain cause or cure.
The Minnesota team recruited 150 men and women patients aged 10 to 65, from six broad ethnic groups, and tested their vitamin D levels.
All of the African American, East African, Hispanic, and American Indian patients had deficient levels of vitamin D: specifically, 20 ng/mL (nanograms per milliliter) of vitamin D or less.
And 93 percent of all the muscle-pain patients had deficient blood levels of vitamin D (12.08 ng/mL on average), with no differences detected between non-immigrants and immigrants, or between men and women. The severity of deficiency was greatest among young women, East Africans, and African Americans.
In addition, 28 percent of all patients were severely deficient in vitamin D (8 ng/mL or less).
Unsurprisingly, the researchers concluded that people with chronic, non-specific muscle pain are very likely to lack sufficient vitamin D. And the deficiency was not limited to people normally considered at low risk for vitamin D deficiency, such as elderly and housebound individuals.
While they could not conclude that vitamin D deficiency was causing the muscle pain, they wisely suggested that doctors screen all patients with this kind of muscle pain for vitamin D status, if only to prevent its associated problems, from weak bones to increased cancer risk.
Sources
- Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA. 2006 Dec 20;296(23):2832-8.
- Grant WB. Epidemiology of disease risks in relation to vitamin D insufficiency. Prog Biophys Mol Biol. 2006 Sep;92(1):65-79. Epub 2006 Feb 28. Review.
- Kamen DL, Cooper GS, Bouali H, Shaftman SR, Hollis BW, Gilkeson GS. Vitamin D deficiency in systemic lupus erythematosus. Autoimmun Rev. 2006 Feb;5(2):114-7. Epub 2005 Jun 21. Review.
- Soilu-Hanninen M, Airas L, Mononen I, Heikkila A, Viljanen M, Hanninen A. 25-Hydroxyvitamin D levels in serum at the onset of multiple sclerosis. Mult Scler. 2005 Jun;11(3):266-71.
- Plotnikoff GA, Quigley JM. Prevalence of severe hypovitaminosis D in patients with persistent, nonspecific musculoskeletal pain. Mayo Clin Proc. 2003 Dec;78(12):1463-70.
