More than 14,000 members of MyMSTeam report that they take vitamin D supplements. They’re not alone — according to Dr. Michael Kornberg, an assistant professor of neurology at Johns Hopkins University, almost all Americans are vitamin D-deficient.

Is this lack of vitamin D a cause of multiple sclerosis (MS), and could taking supplements prevent MS or ease its symptoms? MyMSTeam recently spoke with Dr. Kornberg so he could answer these questions and help people living with MS better understand the role that vitamin D plays in the condition.

What Is Vitamin D?

Vitamin D plays several roles in health. It helps the gut absorb calcium, which is essential for bone health. Vitamin D also helps control cell growth, affects neuromuscular and immune function, and reduces inflammation.

Your body naturally produces vitamin D through sun exposure. However, it’s not always easy — or safe — to soak up the sun. You may live in an area without many hours of sunlight, or you might not be able to go outside very often. When you do go outside, your clothing and sunscreen can block the sun’s rays. This is great for preventing skin damage and skin cancers, but it can prevent vitamin D absorption. Other factors, such as obesity or aging, can make it challenging to keep vitamin D at adequate levels.

Vitamin D deficiencies have been linked to the development of multiple health conditions, including rickets and osteoporosis. Researchers have also found that vitamin D may have an association with several autoimmune diseases, including MS.

Do Low Vitamin D Levels Cause MS?

Some correlation has been observed between vitamin D levels and MS. People from countries with lower levels of sunlight have higher risk factors for developing MS. In addition, a study of more than 7 million U.S. military personnel found that, among white study participants, those who had higher levels of vitamin D were much less likely to go on to develop MS than those with low levels. (Study participants of other races did not show the same effects; this may be due to genetic factors, or it simply could be that the sample sizes of people of other races studied were not large enough to find an association.)

Some researchers suggest that vitamin D’s positive impact on the immune system could explain a correlation between MS and the vitamin.

Can Vitamin D Supplementation Help Prevent MS?

It’s unclear whether increasing vitamin D levels with supplements actually lowers the risk of developing MS. “There's actually a lot of evidence [indicating] that people with MS are just genetically predisposed to having lower vitamin D,” Dr. Kornberg said. “Low vitamin D might be more of an association than a cause.”

Researchers think that the sun exposure associated with higher vitamin D levels might have effects that curb the risk of developing MS, because sunlight helps suppress the immune system activity that causes MS. In other words, it might be the sun, not the vitamin D, that keeps MS from developing.

Still, if you’re worried about developing MS, increasing your vitamin D levels is a good way to improve your overall health, even if it’s not necessarily a way to prevent MS. “I generally do recommend vitamin D supplementation,” Dr. Kornberg said. “If you're supplementing with normal amounts, it's very low risk.”

Can Taking Vitamin D Help People With MS?

Currently, scientific research is unclear on the role of vitamin D supplements in easing symptoms and halting MS activity and disease progression. Some clinical trials have shown evidence that vitamin D supplements helped reduce the physical effects of MS and the risk of relapses, but these studies had small numbers of participants and used widely varying dosages of vitamin D. Other reviews of studies have found different results. According to a Cochrane meta-analysis, vitamin D supplements do not affect MS disability progression or relapse rates.

Some MyMSTeam members report improvement after taking vitamin D supplements. “It made a world of difference to my whole health,” one MyMSTeam member said. “My memory and response times improved, and no more slurring words.”

Another member said, “I take vitamin D and try to sit in the sun a bit every day. They say it helps. I think so.” Other members said that they didn’t want to feel as if a lack of vitamin D caused them to develop MS. In response to a study that stated that vitamin D levels didn’t affect MS symptoms, a MyMSTeam member said, “On a positive note, I don't need to feel like my life of living like a vampire (office worker that commutes in the dark and doesn't see the light of day) ‘caused’ me to get MS.”

How Can You Get More Vitamin D?

It’s usually best to get your vitamins through what you eat, if possible. However, it’s difficult to increase your vitamin D intake through food alone, as only a few foods, such as fish and eggs, naturally contain vitamin D. In some countries, certain foods, like milk, are fortified with vitamin D, but this fortification can be unreliable, prompting many people to use supplements to maintain adequate vitamin D levels.

According to the Institute of Medicine, adults up to age 70 should take at least 600 international units (IUs) of vitamin D per day. Adults older than 70 should get at least 800 IUs of vitamin D daily.

People taking vitamin D supplements should aim to have a blood level higher than 40 nanograms per milliliter, Dr. Kornberg said. “There are a number of ways that you can take vitamin D as a supplement to achieve this level,” he said. “The traditional way is taking high-dose vitamin D2 once a week — specifically, 50,000 IUs of vitamin D2 weekly. Another option is a form of vitamin D called vitamin D3, which is usually taken on a daily basis. People generally take a daily dose of between 1,000 and 5,000 units of vitamin D3,” he said.

As Dr. Kornberg noted, there are two types of vitamin D supplementation: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both types are useful for raising vitamin D levels, although there is evidence that vitamin D3 is more resistant to varying temperatures and humidity and is considered to be more potent than vitamin D2. Vitamin D3 is derived from animal products (sheep’s wool), while vitamin D2 is plant-based — a factor that may be important to know for those following plant-based diets. Whichever form of vitamin D you take, the most important part of taking supplements is consistency.

Using Vitamin D Supplements Safely

With the right doses, vitamin D supplements are safe to take. However, an overly high level of vitamin D can cause a condition called hypercalcemia, in which the calcium levels in the blood are too high. Hypercalcemia can cause kidney stones and harm the bones. In addition, taking more than 4,000 IUs of vitamin D per day may cause gastrointestinal symptoms (such as nausea, vomiting, and constipation), weight loss, weakness, heart problems, and kidney damage.

Vitamin D supplements also may interact with other drugs, such as the cholesterol treatment Lipitor (Atorvastatin), the heart medicine Lanoxin (Digoxin), steroids, thiazide diuretics, and stimulant laxatives. If you’re taking other medications, speak with your doctor before starting vitamin D supplements to find out if they’re right for you and what a safe dosage will be. Always talk to your medical care team before starting a new nutritional, vitamin, or herbal supplement.

You Are Not Alone: Finding Support for MS

MyMSTeam is the social network for people with multiple sclerosis and their loved ones. On MyMSTeam, more than 161,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you curious about whether vitamin D supplements or more sunlight might be impacting your MS symptoms? Have you seen changes after boosting your vitamin D levels? Share your experience in the comments below, or start a conversation by posting on your Activities page.