A discussion organised by the Consortium of Multiple Sclerosis Centres (CMSC) has considered the role of vitamin D in multiple sclerosis (MS).
Researchers concluded that, while evidence is only circumstantial as to the vitamin’s ability to prevent relapses, its multiple health benefits justify its recommended use by all MS patients.
Discussion concerning the link between MS and vitamin D was conducted by Dr Emmanuelle Waubant, a professor of Clinical Neurology and Paediatrics at the University of California, San Francisco, and Dr Ellen Mowry, an associate professor of Neurology and Epidemiology at Johns Hopkins University in Baltimore, and moderated by June Halper, the chief executive officer of CMSC.
According to Dr Waubant, research on the role of vitamin D in MS needs to take several factors into account, in addition to vitamin intake. Transport proteins, enzymes, hormones, and transcription factors are involved in the processing of vitamin D, and might affect the outcomes of supplements consumed.
Nevertheless, the vitamin has receptors scattered throughout the body, including on immune cells such as microglia, macrophages, and B- and T-cells — all key components of MS pathology.
Scientists know that vitamin D is crucial for many aspects of the immune response, and studies have shown that its levels in patients’ blood can determine the frequency and severity of infections. On the cellular level, vitamin D prompts cells to take on a more anti-inflammatory appearance, by secreting less inflammatory and more anti-inflammatory signalling factors. It also shifts T-cell composition to a more anti-inflammatory state, and prevents activated T-cells from entering the brain.
There is, therefore, little doubt that vitamin D provides a range of valuable health effects — effects of importance to everyone, but of particular importance to people with MS.
An entirely different question is whether vitamin D has specific benefits in MS, either by preventing disease development or by hindering relapses in people who are already ill.
Studies showed that children who have lower vitamin D levels more often develop MS as adults. And, as Dr Waubant pointed out, the supplement levels often recommended in children to prevent deficiency syndromes, like rickets, are far lower than those recommended for children at high risk of developing MS.
Several observational studies also demonstrated that MS patients who have higher blood levels of vitamin D tend to relapse less frequently, according to Dr. Mowry. These studies often find a linear relationship between the two — that is, for every unit of increase in vitamin D levels, the risk for relapse decreases accordingly.
Studies using magnetic resonance imaging (MRI) to determine MS progression have also seen a link between blood levels of the vitamin and the prevention of new lesions. One study showed that vitamin D levels were linked to the loss of gray matter in the brain. If these results are confirmed in other studies, they would indicate that vitamin D has rather strong neuroprotective properties.
“Since loss of neurons seems to drive MS progression, perhaps vitamin D could be … test[ed] in individuals with progressive MS to see if it has any impact on worsening in those patient populations,” said Dr Mowry.
One study did test the safety of high-dose supplements. Participants receiving up to 40,000 IU per day did not have a dangerous increase in serum calcium levels, the scenario clinicians worry about when prescribing high doses of vitamin D. However, Dr Waubant warned MS patients against increasing the dose of supplements on their own, as there are no studies investigating long-term effects of very high doses — and too much of a potentially good thing does not necessarily produce better effects.
A particular group of patients needs to be mentioned in this context — pregnant women with MS. Currently, no studies have explored relapse risk and vitamin levels in this group, although neurologists recommend a 50 percent to 100 percent increase in supplementation.
“OBGYNs tend to be conservative about vitamin D, because there are some data in animal models of pregnant animals [showing] that too high vitamin D levels could have a negative impact on the development of the nervous system. But we’re talking here about levels that are really way below that risk,” Dr Waubant said.
Nevertheless, the findings are observational only, and cannot tell us anything about the cause of a lowered relapse risk. The association between higher vitamin D blood levels and lower relapse rates might be explained by other factors, such as UV-light or melatonin, another factor produced in the skin that is dependent on sunlight. Studies have shown that UV-light seems to be protective in MS, independent of vitamin D levels.
To really conclude that vitamin D impacts the disease, randomized prospective clinical trials are needed. One such trial, the VIDAMS study, is currently underway. The study explores if high-dose supplements — 5000 IU per day — differ from standard 600 IU/day treatment in terms of relapse prevention and MRI measures. (This study, being conducted at a number of U.S. sites, is actively recruiting patients.)
It is crucial for researchers to investigate vitamin D’s impact, regardless of underlying MS treatment. One study found an effect in MS patients receiving interferon beta, but not in non-treated patients. This line of inquiry has not been explored with other treatments.
Studies also need to explore if effects differ depending on gender and ethnicity. Dark-skinned people have a lower production of vitamin D when exposed to sunlight, and physicians sometimes report they also have poorer outcomes.
A key point underscored by the researchers is the need for patients to stay on the supplements prescribed them. “It’s not something that you can just sort of rebuild the bank and then it’s fine. You really have to continue on the vitamin D if you want your levels to be maintained at a specific level,” Dr. Mowry said.
Many patients prefer to improve their vitamin D levels naturally, rather than by taking supplements. Studies, however, show that this is not an easy task considering modern lifestyles. “So, it’s pretty rare to find somebody who is able to maintain an adequate vitamin D level from food alone,” said Dr. Mowry.
The researchers also agreed that it is not advisable to stop taking supplements even during the summer months, when people spend more time in the sun.
“In terms of sun exposure, I think really we tend to overestimate the amount of sun exposure that we’re receiving, in terms of how much can have an effect on the vitamin D levels,” Dr Waubant concluded.
The possible link between MS and vitamin D levels will also be discussed at the CMSC 2016 Annual Meeting in Maryland on June 1–4.
Source: Multiple Sclerosis News Today © Copyright 2014 - 2016 BioNews Services, LLC (26/04/16)