A new report says while vitamin D provides a range of health benefits to people, many may not be getting enough to reap its rewards. Among the potential benefits of the vitamin is its ability to stave off the symptoms of multiple sclerosis.
The report was released in the May issue of the Mayo Clinic Health Letter.1
But the vitamin is primarily being evaluated for people who haven't currently been diagnosed with MS, not for those who already have the disease.
A Vital Vitamin
Vitamin D is a fat-soluble vitamin found in both food and made naturally in the body. It can also be derived naturally from exposure to ultraviolet rays from the sun. That's because the UV rays trigger vitamin D synthesis in the skin.
The vitamin exists in several forms, the most active of which is known as calciferol (cal-SIH-fer-awl). Vitamin D's most active function in the body is to maintain normal blood levels of calcium and phosphorus. Boosting calcium levels helps keep bones strong. The vitamin also works in sync with other nutrients, minerals, hormones and the like to improve bone calcification.
Certain foods contain good sources of vitamin D. Some of the best foods, which contain 90% of the recommended daily allowance (RDA) is 3.5 ounces of cooked salmon, 3.5 ounces of cooked mackerel, and 3 ounces of tuna fish. Other sources include milk, margarine, pudding made with milk, and ready-to-eat cereals.2
MS Prevention?
Additionally, scientists have been studying the benefits of vitamin D as a potential preventive approach for people at risk of developing multiple sclerosis.
In a study by doctors at the University of Wisconsin,3 giving a group of mice supplements of vitamin D a day before inducing a disease similar to MS that's typically used in animal experiments known as experimental encephalomyelitis (EAE) "prevented the appearance of any disability whatsoever."
Next, the investigators wanted to know if vitamin D supplementation halted EAE progression. After inducing the experimental disease in the animals, they were given injections of vitamin D more than a week later. For 40 days after the start of the study, the researchers found that the vitamin D treatment halted progression of the disease, and limited its severity. A second group of mice injected with a solution that did not contain vitamin D showed signs of much more severe EAE by the end of the study.
Environmental Benefits
In addition to animal studies, it's well known that the prevalence of MS is highest in parts of the world where the sun's supplies of vitamin D are limited, such as in the Northern Hemispheres of the world farther from the equator. Cases of the disease are lower in tropical zones, by contrast.4 Based on these findings, adequate vitamin D intake "throughout the year may be beneficial for patients with MS, both to obtain immune-mediated suppression of disease activity, and also to decrease disease-related complications, including increased bone resorption, fractures, and muscle weakness," wrote a team of doctors in the Netherlands in a 2004 review paper.5
The theoretic protective effect of vitamin D against MS has also been studied in people. Last year,6 doctors assessed the risk of MS relative to dietary intake of the nutrient in more than 187,000 women who had previously taken part in two large, unrelated studies—the Nurses' Health Study and the Nurses' Health Study II, which took place collectively from 1980 to 2001.
Of these women, 173 women developed multiple sclerosis during the follow-up study. The researchers discovered that the higher the consumption of vitamin D in the diet, the lower the risk of MS. The same held true for those women who had taken vitamin D supplements, the investigators reported. "These results support a protective effect of vitamin D intake on risk of developing MS," wrote the study authors in the Harvard School of Public Health in Boston.
This doesn't mean you should necessarily supplement your diet with large amounts of vitamin D to treat MS. Most studies have looked only at the vitamin as a preventive therapy. In addition, too much vitamin D can be toxic, experts warn. Since the vitamin is fat-soluble, your body doesn't immediately release it, and over time, it can build to potentially toxic levels. This doesn't happen as much from dietary consumption of the vitamin (unless large amounts of cod liver oil are consumed), but from supplements. The warning signs of vitamin D toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. It can also boost levels of calcium in the blood, causing cognitive or heart rhythm abnormalities.7
The Institute of Medicine has established upper tolerable limits of vitamin D at 1,000 IU per day for infants up to 1 year of age, and 2,000 IU daily for children, adults, and pregnant and lactating women.7
In the meantime, research in this area is still ongoing. The National MS Society says it has funded an Australian study being planned that will evaluate the link between ultraviolet radiation exposure and MS diagnosis or a single attack of MS symptoms. Additionally, doctors at the University of Wisconsin are studying why vitamin D apparently reverses or prevents EAE in mice.4
1. Mayo Clinic Health Letter. 2005 May.
2. National Institutes of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Vitamin D. Available at: http://ods.od.nih.gov/factsheets/vitamind.asp. Accessed May 20, 2005.
3. Cantorna MT, Hayes CE, DeLuca HF. 1,25-Dihydroxyvitamin D3 reversibly blocks the progression of relapsing encephalomyelitis, a model of multiple sclerosis. Proc Natl Acad Sci USA 1996 Jul 23;93(15):7861-4.
4. National Multiple Sclerosis Society. Inside MS. More Sunlight, Less MS? Available at: http://www.nationalmssociety.org/IMSJan04-Sunlight.asp. Accessed May 27, 2005.
5. VaAmerongen BM, Dijkstra CD, Lips P, Polman CH. Multiple sclerosis and vitamin D: an update. Eur J Clin Nutr 2004 Aug;58(8):1095-109.
6. Munger KL, Zhang SM, O'Reilly E et al. Vitamin D intake and incidence of multiple sclerosis. Neurology 2004 Jan 13;62(1):60-5.
7. National Institutes of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Vitamin D. Available at: http://ods.od.nih.gov/factsheets/vitamind.asp#h6. Accessed May 27, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
