Vitamin D Slows Disease Activity in Early-Stage Multiple Sclerosis

• Loss of myelin disrupts communication and leaves lasting damage — When myelin is damaged, the underlying nerves become exposed and vulnerable, leading to a breakdown in communication between the brain and muscles, organs, or other systems. This process disrupts normal function and leaves behind scar tissue, known as lesions, which are seen on MRI scans.⁵

• Symptoms vary widely and depend on where nerve damage occurs — The symptoms of MS vary widely from person to person depending on where the damage occurs in the nervous system. Some people experience numbness, tingling, or muscle weakness, while others develop vision problems, difficulty walking, or cognitive issues like memory loss or brain fog.⁶

• Relapses and remissions often define early MS — Symptoms often appear in flare-ups, known as relapses, followed by periods of recovery, but over time, the damage becomes more constant and harder to reverse. In more advanced stages, MS leads to significant disability, making early detection and treatment essential.⁷

• Early MS goes unnoticed until damage is already underway — Another hallmark of MS is that it often begins silently, with damage accumulating in the nervous system before symptoms are noticeable. This early phase is sometimes called clinically isolated syndrome (CIS), and it can be the first sign that a person is on the path to developing MS.⁸ About 85% of people with CIS eventually go on to develop MS.⁹

• Current treatments suppress immune activity but don’t repair damage — These include disease-modifying drugs that suppress or regulate immune activity, which reduce relapse frequency and slow the development of new lesions.

However, many of these medications come with serious side effects, such as increased risk of infections or liver damage. They also do little to repair existing damage or protect nerves from future injury, highlighting the need for therapies that go beyond immune suppression.^10,11

• Very high doses of vitamin D were used — Half of the participants received 100,000 IU of vitamin D, specifically cholecalciferol or vitamin D3, every two weeks for two years, while the other half received a placebo on the same schedule. This dose is roughly 20 times higher than what you’d find in an average over-the-counter supplement, given under close medical supervision to monitor safety and effectiveness.

• Vitamin D reduced relapse and disease activity on MRI scans — The main goal of the study was to see whether participants developed any new symptoms or signs of disease activity on MRI scans during the 24-month period. In the vitamin D group, 60.3% experienced either a relapse or new lesions on MRI, compared to 74.1% in the placebo group.

• Vitamin D doubled the time before new disease activity appeared — Even more telling, those on vitamin D went an average of 432 days before showing disease activity. Meanwhile, those on placebo showed activity after just 224 days, revealing a far quicker disease progression.

• MRI scans show vitamin D reduced inflammation and nerve damage — Imaging results offered additional support for vitamin D’s impact on slowing disease progression. Only 46.2% of people in the vitamin D group developed new lesions, compared to 59.2% in the placebo group.

When it came to more aggressive disease activity, just 18.6% of those on vitamin D showed these signs, versus 34% in the placebo group. These differences show that vitamin D not only delayed the symptoms, but it also reduced inflammation and nerve damage that could be seen on brain scans.

• High-dose vitamin D was safe and well tolerated — Importantly, the treatment appeared safe even at high doses. Although there were more severe adverse events in the vitamin D group compared to the placebo group, none of these were linked to the supplement itself. In other words, the events were unrelated to the high-dose vitamin D and were likely due to other causes.

• Vitamin D stimulates the cells that rebuild myelin — One of vitamin D’s most important roles in MS is its ability to stimulate the growth of oligodendrocytes, the cells that produce myelin. In laboratory and animal studies, vitamin D boosted the number of neural stem cells and increased their conversion into myelin-producing cells.

In rats with damaged myelin, treatment with vitamin D3 raised the number of oligodendrocyte progenitor cells at the injury site and increased levels of key myelin proteins like MBP (myelin basic protein) and PLP (proteolipid protein). This effect was seen in toxin-based injury models as well as in autoimmune MS-like models, which more closely mimic the human disease process.

• It boosts neurotrophins that drive brain repair and cell survival — Neurotrophins are specialized proteins that help brain cells grow, survive, and repair themselves.

These molecules are known to enhance both neurogenesis (new neuron formation) and oligodendrogenesis (new myelin cell formation). In essence, vitamin D creates a more nurturing environment for repair by promoting the production of molecules that heal damaged brain tissue.

• Vitamin D reprograms microglia from destroyers to healers — Another key finding involves vitamin D’s influence on microglia, the immune cells that patrol the brain. In MS, microglia often switch into a destructive state (called the M1 phenotype) that releases inflammatory signals and toxins.

Vitamin D shifts these cells away from that pro-inflammatory state and toward a healing one (the M2 phenotype), which helps clear debris and supports regeneration. Studies showed that vitamin D reduced markers of inflammation like TNF-α and IL-6 while boosting anti-inflammatory signals like IL-10 and TGF-β1, both of which help protect nerve cells and support remyelination.

• It calms astrocytes and helps protect the blood-brain barrier — Astrocytes, another type of brain cell involved in MS, also respond positively to vitamin D. When brain tissue becomes inflamed, astrocytes multiply and contribute to scarring and further damage.

Vitamin D helps dial down this response, decreasing the number of reactive astrocytes and reducing their production of harmful molecules like nitric oxide and vascular endothelial growth factor (VEGF). This shift reduces direct damage to neurons and stabilizes the blood-brain barrier, the brain’s defense system that is often compromised early in MS.

• Vitamin D strengthens the brain’s first line of defense — The review also highlighted vitamin D’s ability to reinforce the blood-brain barrier itself. The active form of the vitamin increased the expression of tight junction proteins that seal the spaces between endothelial cells and block harmful substances from entering the brain.

It also reduces the production of cell adhesion molecules that would normally allow immune cells to sneak into the brain. In mouse models of MS, vitamin D treatment led to fewer immune cells entering the central nervous system, lower rates of demyelination, and reduced oxidative stress.

• It helps defend brain cells from oxidative stress — In both animal and cell studies, vitamin D lowered reactive oxygen species (ROS) levels and increased the activity of antioxidant enzymes like glutathione peroxidase and superoxide dismutase. It also increased the expression of Nrf2, a master regulator of your body’s internal antioxidant defenses.

These changes reduce cellular wear and tear and create a biochemical environment that supports healing instead of degeneration. Taken together, the evidence supports vitamin D’s emerging role as a powerful neuroprotective agent in MS.

1. Sensible sun exposure is the ideal way to optimize vitamin D — Research shows that people who live closer to the equator and are exposed to higher amounts of sunlight all year-round have a lower risk of MS.¹⁴ However, if your diet contains large amounts of seed oils, extra caution is needed.

These oils, rich in linoleic acid (LA), an omega-6 fatty acid, oxidize quickly under UV light. This reaction on your skin’s surface generates breakdown byproducts that promote inflammation and damage cellular structures, including DNA. If you’ve been consuming seed oils regularly, it’s best to reduce your intake for four to six months before increasing sun exposure.

During this time, limit sunlight to early morning or late afternoon, avoiding peak hours between 10 a.m. and 4 p.m. People with higher body fat may require additional time for LA to clear from tissues, since LA is stored in fat and released slowly.

Those with darker skin will also need longer exposure times to produce the same amount of vitamin D as those with lighter skin. Use the “sunburn test” as a guide — monitor your skin and avoid any redness. Staying below that threshold helps ensure you’re getting the benefit without harm.

2. Take high-quality vitamin D3 if necessary — For individuals living in northern climates or those with limited sun exposure, supplementing with high-quality vitamin D3 is often necessary to achieve and maintain optimal vitamin D levels.

Vitamin D3 is synthesized naturally in your skin when it’s exposed to sunlight, specifically ultraviolet B (UVB) rays. On the other hand, vitamin D2 is typically derived from plant sources, including yeast and mushrooms exposed to UV light.

While both forms are available as supplements, research has uncovered distinct differences in their effectiveness. Vitamin D3 is significantly more effective than D2 at raising blood vitamin D levels.¹⁵ Testing your vitamin D levels is necessary to ensure you’re taking the right amount of vitamin D3.

3. Maintain optimal vitamin D levels through regular testing — Testing your vitamin D status twice per year allows you to adjust your sun exposure and supplementation to stay in the optimal range. For neurological health and immune balance, aim for serum levels of 60 to 80 ng/mL (150 to 200 nmol/L).

4. Optimize vitamin D metabolism with synergistic nutrients — It’s important to understand that magnesium, calcium, vitamin D3, and vitamin K2 must be properly balanced for optimal overall health. Focus on a nutrient-dense diet with foods rich in these synergistic nutrients, but consider supplementation if needed.