Please could you give a brief introduction to vitamin D and its role in the body?
Vitamin D is actually a hormone. For the most part, humans obtain vitamin D through sun exposure. Ultraviolet light from the sun promotes the conversion of a compound in the skin to pre-vitamin D. Through a series of processes in the body, it is eventually converted to the main storage form of vitamin D. The storage form is converted into the active form as various body parts need it.
One of the biggest roles of vitamin D is to help the body regulate calcium levels. A control enzyme in the kidney helps convert the storage form of vitamin D to its active form in order to do this. However, this enzyme exists in other parts of the body where vitamin D is needed, including the immune system and the brain.
Please could you describe the symptoms of multiple sclerosis (MS) and explain what causes them?
Multiple sclerosis (MS) occurs in people with certain genes who are exposed (or not exposed) to things in the environment that appear to influence the risk of the disease. For example, cigarette smoking appears to increase the risk of getting MS. Low vitamin D also predisposes people to getting MS. These genetic and environmental factors create a “perfect storm” that leads to the immune system not working correctly and ultimately causing MS.
The immune system normally works to help do things like attacking viruses and other infectious agents that enter our bodies. In autoimmune diseases such as MS, the immune system is tricked into thinking that parts of the normal body are supposed to be attacked.
The brain and spinal cord functions like a big electrical grid, and the nerve cells have “wires” that are coated by a substance called myelin, which helps the electrical signal move faster along the wires. In MS, this coating is periodically stripped off the nerves. When this happens, the signal can’t get through well, if at all. When the coating is stripped off in an area of the brain or spinal cord that controls things we do or sense, then symptoms emerge. When the body repairs the area, the symptoms may go away fully or completely.
The areas in the nervous system that are affected by MS can be seen on magnetic resonance imaging (MRI) as white “spots” in specific areas of the brain and spinal cord. Sometimes in a person with MS, particularly in the brain, these white spots are found even though no new symptoms had occurred.
Symptoms of MS for most people with the disease usually come in “attacks,” also called “relapses.” These attacks last for at least 24 hours (and usually for several days or weeks). Symptoms during an attack may include numbness, weakness, imbalance, trouble walking, trouble seeing out of one eye, or double vision. Many people may have similar symptoms due to other causes, though, because many diseases can affect the same control areas of the nervous system.
How did your research into vitamin D levels and multiple sclerosis originate?
Others had already shown that low vitamin D increased the risk of getting MS. We wondered if low vitamin D makes MS worse in people who already have the disease, or if it was too late for vitamin D to have an impact once the disease had begun.
In a prior study, we looked at vitamin D levels in children with MS and showed that those who had higher levels of vitamin D in the blood had fewer MS attacks. We didn’t have routine MRI scans, though, so we didn’t know if vitamin D levels correlated with white spots on brain MRI.
What did your research involve?
In this study, we looked at a group of 469 people with MS who had had clinical exams, brain MRI scans, and blood draws every year for 5 years. We measured the vitamin D levels in the blood each year and looked to see if the level at the beginning of each year was associated with having new MS spots in the brain (seen on MRI) by the end of that year.
What we saw was that higher levels of vitamin D did in fact correspond with lower numbers of new spots over the course of the five-year study.
Your research showed that lower levels of vitamin D are associated with a more active disease state in people with multiple sclerosis. Did your research determine whether this association was causative?
This study is not able to prove causation. Since we looked at whether vitamin D levels were associated with later developing new spots, it is less likely that “reverse causality” is occurring (i.e. that people with more active MS somehow have lower vitamin D levels). However, in order to prove causation, a randomized trial of vitamin D supplementation is needed. In fact, we are currently conducting a trial now to answer this very question.
Is there a plausible mechanism by which low vitamin D levels could cause worse multiple sclerosis symptoms?
We know that vitamin D impacts the immune system in several ways, usually moving it away from being in more of an “attack” mode, so it is entirely plausible that vitamin D may impact how active MS is.
Would taking vitamin D supplements prevent these symptoms?
We don’t know yet. Since we haven’t proven causality; it could be a coincidence that vitamin D levels seem to be inversely related to new white spots in the brain in people with MS. The clinical trial of vitamin D supplementation we are currently doing will help to answer that question.
Are there any potential dangers of taking vitamin D supplements?
Yes. Even though vitamin D supplements are available over the counter, vitamin D is still a drug. One of the most concerning potential dangers is high calcium in the blood and urine, which can have many potential bad effects, including causing heart rhythm problems or kidney stones. Since we have not yet proven that they are helpful, taking supplements is something each person should discuss with his or her doctor.
What plans do you have for further research in this field?
In addition to doing the clinical trial I mentioned, we are trying to understand how vitamin D specifically impacts the immune system and genes in people with MS.
How do you think the future of treatments for MS will develop?
There are many treatments for MS that have recently been developed or are currently under development. One challenge is that over time in MS, damage to the nerves can occur in addition to damage to the coating around the nerves. When enough nerve damage occurs, people with MS may have a slow decline in memory, walking, or vision. The current MS treatments do not seem to help much, if at all, once this decline begins. We have some suggestion that higher vitamin D levels are associated with less of a decline, but these data are preliminary.
Where can readers find more information?
More information about the vitamin D clinical trial can be found at:
http://www.clinicaltrials.gov/ct2/show/NCT01490502?term=vitamin+d+and+multiple+sclerosis&rank=6
About Ellen Mowry
Dr. Mowry is an Assistant Professor of Neurology at Johns Hopkins University. She completed medical school at the University of Rochester and a neurology residency at the University of Pennsylvania. After doing a fellowship in multiple sclerosis at UCSF, she joined the faculty there before moving to her current position.
Dr. Mowry’s research focuses on understanding how factors in the environment, many of which can be modified, influence the risk of MS as well as its prognosis. It is her hope that by identifying such factors, changes the way people are exposed to them can reduce the risk of MS and improve the disease for people who already live with it.
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