Vitamin D update

Subject:  Vitamin D may provide protection against developing Multiple Sclerosis, rheumatoid arthritis and other diseases.  This may explain the latitudinal variation in MS and increasing incidence with age in RA.

A piece of medical trivia that has always bugged me is the distribution of multiple sclerosis (MS).  Historically MS has been a disease of "Place."  The further from the equator you lived, the more likely you were to get it.  There is also a genetic component to MS incidence; certain populations that are more prone to developing the disease. This pattern has decreased in recent years as different population groups have migrated and as a result MS has become a disease of "race and place."

A recent paper from the Harvard School of Public Health suggests that Vitamin D may protect against MS.[1]  If so, this offers a possible explanation for the latitudinal variation sometimes seen in MS.  Researchers examined the data collected from the Nurses' Health Studies in which over 187,000 women were followed. Women who received over 400 IU of vitamin D a day from diet and supplements had a 41% lower chance of getting MS.  The same group of researchers had previously looked at antioxidant vitamins, (A, beta carotene, C, and E) and seen no protective benefit against MS.[2]

Vitamin D is manufactured in the skin when exposed to ultraviolet radiation from sunlight.  The closer to the equator one lives the more sun exposure and the more vitamin D made.  The further from the equator the less vitamin D is made.

Another recent study noticed a protective effect against rheumatoid arthritis (RA).  Examining the health records of 30,000 women, researchers noted that adequate levels of vitamin D decreased RA incidence by about 30%.[3] Both conditions, MS and RA, are thought to occur when the body's immune system turns against itself. Vitamin D may work by calming overactive immune cells. There is some animal evidence to support this idea. Mice with symptoms like those of multiple sclerosis or rheumatoid arthritis improve with vitamin D treatment.

Vitamin D is a steroid hormone that helps the body absorb and retain calcium. Too much can be toxic, while too little causes brittle bones. The vitamin occurs naturally in some foods, such as liver and fatty fish, and is often added to others. One cup of fortified milk contains about half of the estimated adult daily need. But most of our vitamin D is home grown; the body makes it in response to sunshine. The daily dose can be achieved by soaking up bright sunshine on the face and hands for 15 minutes, three times a week - weather permitting.  Many people, particularly the elderly, are vitamin D deficient.  This may explain why rheumatoid arthritis is more common in the elderly.


There is general agreement that a low vitamin D status is one of the causes of osteoporosis. Low vitamin D can lead to a disturbed muscle function. Besides rheumatoid arthritis and multiple sclerosis, data also show low vitamin D levels play a role in tuberculosis, inflammatory bowel diseases, hypertension, and specific types of cancer. Some intervention trials have demonstrated that supplementation with vitamin D or its metabolites can:[4]
(a) Reduce blood pressure in hypertensive patients;
(b) Improve blood glucose levels in diabetics;
(c) Improve symptoms of rheumatoid arthritis and multiple sclerosis

Information like these studies can leave us confused.  The current popular wisdom is that sun exposure is dangerous because it increases risk of skin cancer.  In avoiding sun exposure are we not opening the door to other risks as yet unclear?  When trying to sort through this balance, of risk versus benefit there is a little detail we must remember.  For still unknown reasons, people feel better with regular sun exposure.[5]  Although this isn't the bottom line, it should count for something.

References:
1 Neurology. 2004 Jan 13;62(1):60-5. Vitamin D intake and incidence of multiple sclerosis. Munger KL, Zhang SM, O'Reilly E, Hernan MA, Olek MJ, Willett WC, Ascherio A.
2 Neurology. 2001 Jul 10;57(1):75-80. Intakes of carotenoids, vitamin C, and vitamin E and MS risk among two large cohorts of women. Zhang SM, Hernan MA, Olek MJ, Spiegelman D, Willett WC, Ascherio A.
3 Merlino, L. A. et al. Vitamin D intake is inversely associated with  rheumatoid arthritis. Arthritis and Rheumatism, 50, 72 - 77, (2004).
4Br J Nutr. 2003 May;89(5):552-72.   Vitamin D in preventive medicine: are we ignoring the evidence?
Zittermann A.
5 BMC Dermatol. 2002 Apr 12;2(1):6.    Impact of UVA exposure on psychological parameters and circulating serotonin and melatonin. Gambichler T, Bader A, Vojvodic M, Bechara FG, Sauermann K, Altmeyer P, Hoffmann K.


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