Multiple sclerosis risk is shaped by controllable environmental factors including vitamin D deficiency, smoking, teenage obesity, low sun exposure, and air pollution, according to Gram Research analysis of a 2026 review. Vitamin D supplementation reduces disease activity in early MS, while adolescence emerges as the critical prevention window when the developing immune system is most vulnerable to these triggers. Both individual actions (maintaining healthy weight, avoiding smoking, getting adequate vitamin D) and public health policies (improving air quality, designing walkable neighborhoods) are necessary for effective prevention.
Multiple sclerosis (MS) isn’t just about genes—your environment plays a huge role in whether you develop this disease. According to Gram Research analysis, scientists have identified several modifiable risk factors including vitamin D deficiency, smoking, obesity during teenage years, air pollution, and UV exposure. The good news? Many of these factors can be controlled through lifestyle changes and public health improvements. A new review in Revue neurologique highlights that adolescence is a critical window when your immune system is most vulnerable, making prevention efforts during teenage years especially important. Researchers found that vitamin D supplementation and maintaining healthy weight during youth could significantly reduce MS risk.
Key Statistics
A 2026 review in Revue neurologique identified six major modifiable environmental risk factors for multiple sclerosis: vitamin D deficiency, low UV exposure, smoking, adolescent obesity, air pollution, and chemical exposures.
Mendelian randomization studies cited in the 2026 review provide strong evidence that vitamin D deficiency and high body weight actually cause increased MS risk, not just correlate with it.
According to the 2026 review, adolescence represents a critical vulnerability window when the maturing immune system is uniquely sensitive to metabolic and environmental MS triggers.
The 2026 review found that vitamin D supplementation stands out as a validated intervention capable of reducing disease activity in people with early multiple sclerosis.
The Quick Take
- What they studied: What environmental factors (things in your surroundings and lifestyle) increase the risk of developing multiple sclerosis, and which ones can be prevented or changed?
- Who participated: This was a comprehensive review of existing research rather than a single study with participants. Scientists analyzed hundreds of studies about MS risk factors across different populations worldwide.
- Key finding: Vitamin D deficiency, smoking, teenage obesity, low sun exposure, and air pollution are major controllable risk factors for MS. Adolescence (ages 13-19) is the most critical time when your body is most vulnerable to these environmental triggers.
- What it means for you: You can reduce your MS risk by maintaining healthy vitamin D levels, avoiding smoking, staying active and at a healthy weight during teenage years, and supporting clean air policies in your community. However, having these risk factors doesn’t guarantee you’ll develop MS—genetics also play a role.
The Research Details
This research is a comprehensive review article, meaning scientists examined and summarized findings from hundreds of existing studies about multiple sclerosis and environmental risk factors. Rather than conducting their own experiment with participants, the researchers looked at patterns across many different studies to identify which environmental factors most strongly influence MS development.
The scientists used a special research method called Mendelian randomization to determine which factors actually cause MS (not just associated with it). This method uses genetic information to prove that certain environmental factors truly increase disease risk, rather than just appearing together by chance.
The review organized findings by life stage, with special attention to adolescence—the teenage years—because this is when the immune system is still developing and appears most vulnerable to environmental triggers.
Review articles are important because they synthesize large amounts of research into clear patterns. By examining many studies together, scientists can identify which risk factors are most important and most changeable. This helps doctors and public health officials focus prevention efforts where they’ll have the biggest impact. The focus on adolescence matters because preventing disease during this critical window could stop MS from developing entirely, rather than just treating it after it starts.
This review was published in a peer-reviewed medical journal (Revue neurologique), meaning other experts checked the work for accuracy. The authors used rigorous methods like Mendelian randomization to establish cause-and-effect relationships, not just correlations. However, as a review article, it synthesizes existing research rather than providing new experimental data. The strength of conclusions depends on the quality of studies reviewed.
What the Results Show
The research identified six major environmental risk factors that can be modified: vitamin D deficiency, low UV exposure, smoking, obesity during adolescence, air pollution, and chemical exposures. Among these, vitamin D deficiency and high body weight showed the strongest evidence of actually causing MS, based on genetic studies.
Vitamin D supplementation emerged as the most proven intervention—studies show it can reduce disease activity in people with early MS. This is significant because it’s an inexpensive, accessible treatment that works through your immune system.
Adolescence (roughly ages 13-19) stands out as a critical vulnerability window. During these years, your immune system is still maturing, making it uniquely sensitive to metabolic changes and environmental triggers. This means prevention efforts targeting teenagers could have outsized benefits.
The review emphasizes that effective prevention requires both individual actions (like taking vitamin D, exercising, avoiding smoking) and broader public health policies (like improving air quality and designing neighborhoods that encourage walking and physical activity).
Beyond MS prevention, the research notes that addressing these environmental factors provides additional health benefits. Maintaining healthy weight, regular physical activity, and avoiding smoking reduce risk for heart disease, diabetes, and certain cancers. Improving air quality benefits everyone’s respiratory and cardiovascular health. These ‘side benefits’ make prevention strategies valuable even for people without MS risk factors.
This review builds on decades of MS research by synthesizing recent findings and highlighting adolescence as a critical prevention window. Previous research identified these risk factors individually; this review connects them and emphasizes their interaction with genetic susceptibility. The use of Mendelian randomization represents a newer, more rigorous approach to proving causality compared to older observational studies.
As a review article, this research doesn’t provide new experimental data—it summarizes existing studies, which vary in quality and design. Some risk factors (like chemical exposures) have less research evidence than others (like vitamin D). The review doesn’t specify exact risk reduction percentages for most interventions. Additionally, most MS research focuses on people of European descent, so findings may not apply equally to all populations. The review also cannot determine how much each factor contributes individually, since they often occur together.
The Bottom Line
Strong evidence: Maintain adequate vitamin D levels (through sun exposure or supplements) and avoid smoking. Moderate evidence: Maintain healthy weight during adolescence and engage in regular physical activity. Emerging evidence: Reduce air pollution exposure and limit chemical exposures where possible. Support public health policies that improve air quality and neighborhood walkability. These recommendations are appropriate for general population health, not just MS prevention.
Everyone should care about these factors for overall health, but they’re especially important for: teenagers and young adults (critical prevention window), people with family history of MS, and anyone living in areas with poor air quality. These recommendations don’t replace medical care for people already diagnosed with MS—they should follow their doctor’s treatment plan.
Vitamin D supplementation may reduce disease activity within weeks to months in early MS. Weight loss and increased physical activity typically show health benefits within 3-6 months. Smoking cessation benefits begin immediately. However, preventing MS entirely through these factors may take years, since MS typically develops in late teens to early 40s. The earlier you start these habits, the better the long-term protection.
Frequently Asked Questions
Can you prevent multiple sclerosis by taking vitamin D supplements?
Vitamin D supplementation reduces disease activity in early MS and is supported by strong evidence. However, it’s not a guaranteed prevention—MS develops from complex interactions between genes and environment. Maintaining adequate vitamin D levels is one important piece of prevention, especially during adolescence.
Why is adolescence so important for MS prevention?
During teenage years, your immune system is still developing and appears uniquely vulnerable to environmental triggers like obesity, smoking, and vitamin D deficiency. Prevention efforts during this critical window may stop MS from developing entirely, making adolescence the optimal time for intervention.
What environmental factors increase MS risk the most?
Vitamin D deficiency and high body weight show the strongest evidence of causing MS. Smoking, low sun exposure, air pollution, and chemical exposures also significantly increase risk. These factors often occur together and interact with your genetic susceptibility.
Can air pollution really increase my risk of multiple sclerosis?
Yes, research shows air pollution is a modifiable MS risk factor. Improving air quality through public policies benefits MS prevention while also reducing heart disease, respiratory disease, and cancer risk—making it valuable for everyone’s health.
If I have a family history of MS, what should I do?
Focus on modifiable factors: maintain healthy vitamin D levels, stay physically active, maintain a healthy weight (especially during adolescence), avoid smoking, and support air quality improvements in your community. These actions reduce MS risk while providing broad health benefits regardless of family history.
Want to Apply This Research?
- Track weekly vitamin D intake (through food, supplements, or sun exposure minutes), weekly physical activity minutes, and monthly weight trends. For smokers, track daily cigarette reduction or quit date.
- Set a specific goal: ‘Get 15-30 minutes of midday sun exposure 3-4 times weekly’ or ‘Take vitamin D supplement daily’ or ‘Walk 30 minutes most days.’ Use app reminders for consistency. For teenagers, gamify physical activity goals with friends.
- Monthly check-ins on vitamin D levels (through blood tests if possible), quarterly weight and fitness assessments, and ongoing smoking status tracking. Long-term, monitor energy levels and overall health markers as indicators of lifestyle improvement.
This article summarizes research on MS risk factors and is not medical advice. Multiple sclerosis is a complex disease involving both genetic and environmental factors; having risk factors does not guarantee disease development. People with family history of MS, symptoms of MS, or existing MS diagnosis should consult with a neurologist or healthcare provider for personalized medical advice. Vitamin D supplementation and lifestyle changes should be discussed with your doctor, especially if you take other medications or have existing health conditions. This review synthesizes existing research but does not replace professional medical evaluation or treatment.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.