There is no proven way to prevent ALS. About 90 to 95 percent of cases are sporadic, meaning they arise without a clear family history, and scientists still don’t fully understand what triggers the disease. The remaining 5 to 10 percent of cases are familial, linked to inherited gene mutations. While a guaranteed prevention strategy doesn’t exist, research has identified several environmental and lifestyle factors that raise or lower your risk, and reducing your exposure to these factors is the closest thing to a preventive approach available today.
Why ALS Is So Hard to Prevent
ALS likely results from a combination of genetic susceptibility and a lifetime of environmental exposures, a concept researchers call the “ALS exposome.” No single cause has been identified for the sporadic form of the disease, which makes targeted prevention nearly impossible at this stage. The National Academies of Sciences has acknowledged that preventing ALS will remain difficult for the near future, but has called for comprehensive research into the environmental triggers that could eventually make prevention realistic.
For the small percentage of people who carry known ALS-related gene mutations, the picture is slightly more hopeful. The first-ever ALS prevention trial, called ATLAS, is currently testing whether early treatment of people carrying a specific mutation (SOD1) can delay or prevent symptoms from ever appearing. This is a landmark shift from treating the disease after diagnosis to intervening before it starts, but it applies only to a narrow genetic group.
Smoking Increases Your Risk
Smoking is one of the most consistent modifiable risk factors for ALS. A pooled analysis of five large prospective studies found that both current and former smokers had roughly a 42 to 44 percent higher risk of developing ALS compared to people who never smoked. The risk increased by about 10 percent for every additional 10 cigarettes smoked per day and by 9 percent for every additional decade of smoking. Starting younger also matters: each five years younger a person was when they began smoking was associated with an 11 percent increase in risk.
If you smoke, quitting is the single most actionable step you can take to lower your ALS risk, on top of its well-known benefits for heart disease, lung cancer, and stroke.
Pesticide and Chemical Exposure
Living or working near heavy pesticide use appears to increase ALS risk. A large U.S. study found statistically significant links between ALS and several common agricultural chemicals. The herbicide glyphosate (the active ingredient in many weed killers) was associated with a 29 percent higher risk. The insecticide carbaryl carried a 32 percent increase, and chlorpyrifos, another widely used insecticide, was linked to a 25 percent increase. Several fungicide groups, including dithiocarbamates, also showed enriched associations with the disease.
These findings don’t mean casual contact with a treated lawn will cause ALS. The strongest associations involve sustained, occupational-level exposure. If you work in agriculture, landscaping, or pest control, wearing proper protective equipment and minimizing direct chemical contact is a reasonable precaution. For the general public, washing produce and being aware of local pesticide application schedules can reduce incidental exposure, though the absolute risk from these levels is small.
Head Injuries and Contact Sports
Repeated head trauma is one of the more striking risk factors. A meta-analysis found that people with a history of head injuries had a 70 percent higher risk of developing ALS. Having more than one head injury tripled the risk, and sustaining head injuries within the previous 10 years was associated with a similar threefold increase. For people with multiple head injuries in the preceding decade, the risk elevation was more than 11-fold.
This connection partly explains why ALS rates are unusually high among professional soccer players and football players. Researchers believe repeated subconcussive impacts, not just full concussions, may contribute. Protecting your head during sports, wearing appropriate helmets, following concussion protocols, and avoiding unnecessary contact drills are practical steps. Injuries to other body parts (arms, legs, trunk) showed no connection to ALS risk, reinforcing that this is specifically about damage to the brain and nervous system.
Military Service and Occupational Hazards
Veterans, particularly those who served in the Gulf War or World War II, appear to face elevated ALS risk. A systematic review of 19 studies found a suggestive association between military service and later ALS development. The likely culprits are a combination of exposures common in military settings: pesticides (including Agent Orange), exhaust fumes, burning agents, heavy metals, and head trauma. The U.S. Department of Veterans Affairs already recognizes ALS as a service-connected disease for benefits purposes.
If you’re currently serving or have served, documenting your exposures and discussing them with a healthcare provider who understands environmental health can be worthwhile, particularly if you have a family history of neurodegenerative disease.
A Toxin in Water and Seafood
An environmental toxin called BMAA, produced by cyanobacteria (blue-green algae), has drawn increasing attention as a possible contributor to ALS. BMAA is found in contaminated seafood, shellfish, drinking water, and recreational waters. Roughly 95 percent of cyanobacteria genera tested produce it. Once ingested, BMAA crosses into the brain, where it gets incorporated into nerve cell proteins in place of a normal amino acid, causing those proteins to misfold. Because neurons don’t divide and replace themselves the way other cells do, damaged proteins accumulate over a lifetime until cells begin to die.
Researchers have found high BMAA concentrations in the brains of people who died from ALS and Alzheimer’s disease, but not in the brains of healthy controls. BMAA also overstimulates nerve cells and works synergistically with methylmercury (a common seafood pollutant) to deplete the body’s main antioxidant defenses. While a direct causal link hasn’t been definitively established, avoiding water sources with visible algae blooms and being cautious about seafood from contaminated areas is a sensible precaution.
Dietary Factors That May Lower Risk
Omega-3 fatty acids show the strongest dietary association with reduced ALS risk. A pooled analysis of large cohort studies found that people in the highest fifth of omega-3 intake had a 34 percent lower risk of ALS compared to those in the lowest fifth. Both plant-based omega-3s (from foods like flaxseed and walnuts) and marine omega-3s (from fatty fish) contributed to the protective effect. Omega-6 fatty acids, by contrast, showed no association either way.
Vitamin E supplementation also shows a potential benefit, but only with long-term use. Taking vitamin E for five or more years was associated with a 36 percent reduction in ALS risk, while short-term use showed no benefit. The trend across durations of use was statistically significant.
The Mediterranean diet, rich in both omega-3s and antioxidants, has been studied in ALS patients. While it favorably changed several inflammatory markers and metabolic hormones, a prospective study found no evidence that it slowed disease progression in people who already had ALS. Its role in prevention before disease onset remains unclear, though its components align with the nutrients that do show protective associations.
Genetic Testing for Families With ALS
If you have a blood relative with ALS, genetic testing can clarify whether you carry a mutation that raises your risk. Current consensus guidelines recommend that all people diagnosed with ALS be offered genetic testing through a panel that includes the four most important genes: C9orf72, SOD1, FUS, and TARDBP. Mutations in C9orf72 are the most common genetic cause of ALS, and SOD1 mutations are now especially relevant because a gene-targeted therapy exists for that specific mutation.
For unaffected family members, genetic counseling can help you understand what a positive or negative result would mean practically. Knowing you carry a mutation doesn’t mean you’ll develop ALS, but it opens the door to monitoring programs and, in the case of SOD1, potential enrollment in prevention trials. These are early days for genetic prevention, but they represent the most concrete progress the field has made.
Putting It Together
No combination of lifestyle changes can guarantee you won’t develop ALS. But the evidence points toward a profile of lower risk: not smoking, minimizing exposure to pesticides and industrial chemicals, protecting your head from repeated injury, eating a diet rich in omega-3 fatty acids, and potentially supplementing with vitamin E over the long term. For people with a family history, genetic testing and counseling offer the most targeted path to early detection and, eventually, prevention. The science isn’t there yet for a definitive prevention protocol, but these steps represent the best available evidence for reducing your risk.