Vitamin D and Multiple Sclerosis
If your New Year’s resolutions include living a healthier lifestyle, one aspect to consider is whether vitamins – aside from their other health effects – provide any benefits in multiple sclerosis (MS).
The best evidence is for vitamin D. The sunshine vitamin is manufactured in the skin by ultraviolet (UV) light (primarily UV-B). This reaction produces vitamin D3 (also called cholecalciferol), which is converted to a biologically active form (called calcitriol) in the kidneys and immune cells. While the main role of vitamin D is to promote healthy bones, this connection to the immune system makes it potentially very interesting for MS.
A number of studies have indicated that vitamin D has important effects on the immune system. It suppresses the activation of T cells, which are known to be key players in MS; shifts the immune response to a less inflammatory profile; and induces other immune cells (called regulatory T cells, or Tregs) to modulate the immune response (Armas and colleagues. J Am Acad Dermatol 2007;57:588-593). It has also been suggested that vitamin D acts to dampen the immune system’s feedback loop to limit the negative effects of inflammation (Hayes and colleagues. Cell Mol Biol 2003;49:277-300).
The recommended dietary allowance (RDA) of vitamin D is about 200 IU/day, or roughly the amount of vitamin D found in a half-teaspoon of cod liver. The RDA is higher for people over age 50 (400 IU/day) and age 70 (600 IU/day). The main source is sunlight. The few foods that naturally have vitamin D include fish, liver, egg yolks and reindeer meat. However, many foods are enriched with vitamin D (milk, soy milk, orange juice, margarine) – which was originally intended to prevent the bone disease called rickets.
Even with a well-balanced diet, it isn’t always possible to reach the RDA of 200-700 IU/day. With low sun exposure in the northern hemisphere during the winter months, most people have some degree of vitamin D deficiency. The problem is even more acute in people with darker skin, which is far less efficient than lighter skin in synthesizing vitamin D. And what little sunlight we do receive is often ineffective at producing vitamin D because of the skin blocks that are commonly used to protect against skin cancer.
As a result, the Canadian Community Health Survey (2004) found that about 80-90% of adults had an inadequate intake of vitamin D – the poorest track record among all the vitamins.
A number of early studies suggested that low vitamin D levels are associated with a higher risk of developing MS (Munger and colleagues. JAMA 2006;296:2832-2838; free full text at http://jama.ama-assn.org/content/296/23/2832.long). A study in the Netherlands also found that vitamin D protected against the development of MS – but only in women (Kragt and colleagues. Mult Scler 2009;15:9-15). Vitamin D levels are typically lower in women compared to men, suggesting that they may be more at risk of vitamin D insufficiency, just as they are more at risk of developing MS. In support of this notion, a study in France found that the connection between sun exposure and MS was much stronger for women compared to men (Pierrot-Deseilligny and colleagues. Brain 2010:133;1869-1888).
So it may be that vitamin D plays a role in MS. But that doesn’t mean that taking supplements (or increasing your sun exposure) will be effective as a treatment. That needs to be looked at separately.
Thus far, some studies have found that people with higher levels of vitamin D have fewer relapses (Smolders and colleagues. Mult Scler 2008;14:1220-1224; Mowry and colleagues. Ann Neurol 2010;67:618-624), and less disease activity seen on MRI (Mowry and colleagues. Ann Neurol 2012;72:234-240). Some studies have also suggested that people with lower sun exposure or lower vitamin D levels have a higher risk of developing disability (Tremlett and colleagues. Neuroepidemiology 2008;31:271-279; D’hooghe and colleagues. Mult Scler 2012;18:451-459; McDowell and colleagues. Neuroepidemiology 2011;37:52-57; Neau and colleagues. Rev Neurol [Paris] 2011;167:317-323, article in French).
However, only four trials have looked at whether vitamin D works as an actual MS treatment and the results have not been encouraging. A one-year trial of people taking an interferon-beta found that adding vitamin D3 reduced disease activity on MRI and had a modest effect on disability, but there was no effect on the rate of relapses (Soilu-Hanninen and colleagues. J Neurol Neurosurg Psychiatry 2012;83:565-571). Two other studies of vitamin D3 supplements found no effect (Kampman and colleagues. Mult Scler 2012;18:1144-1151; Mosayebi and colleagues. Immunol Invest 2011;40:627-639; ). A study of vitamin D2 supplements (which are not as effective as D3 supplements) also found no effect, and people on higher doses (6,000 IU/day) actually did a little worse than people on lower doses (1,000 IU/day) of vitamin D2 (Stein and colleagues. Neurology 2011;77:1611-1618). So more is not necessarily better.
All of the evidence thus far has been systematically analysed and the results have just been published (Pozuelo-Moyano and colleagues. Neuroepidemiology 2012;40:147-153). The conclusion: inconclusive. So the jury is still out on vitamin D for MS. We’ll know more once the results of three ongoing studies (called CHOLINE, SOLAR and EVIDIMS) are released.
In the meantime, daily vitamin D3 may be a help and will do little harm, so you may want to consider taking supplements (2000-4000 IU) – at least during the dark, winter months.
Canadian Community Health Survey: www.hc-sc.gc.ca/fn-an/surveill/nutrition/commun/art-nutr-eng.php#a3
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