Researchers are increasingly investigating whether certain supplements and medications developed for other purposes might help reduce the risk of Alzheimer’s disease.
Some are valuable for general health, including omega-3s, magnesium, vitamin D, and creatine. Others are particularly intriguing as possible repurposed drugs, including low-dose lithium, metformin, GLP-1 drugs, ezetimibe, and PDE5 inhibitors such as tadalafil (Cialis). Research suggests several possible pathways—including better metabolic and vascular health and effects on inflammation, brain energy, and cellular cleanup mechanisms.
The most important strategy remains addressing established risk factors such as Insulin Resistance, high blood pressure, abnormal lipids, physical inactivity, poor sleep, smoking, and nutritional deficiencies.
The research is encouraging, but an important distinction remains: none of these supplements or medications has yet been established as a treatment that cognitively healthy people should take specifically to prevent Alzheimer’s disease.
Omega-3 fatty acids—particularly DHA (docosahexaenoic acid)—are important components of brain-cell membranes and play important roles in brain, cardiovascular, and overall health.
APOE4 may affect how DHA is transported and metabolized, and researchers are studying whether maintaining adequate DHA status may be particularly important for APOE4 carriers.
Studies have found associations between eating fish and better cognitive health, and higher DHA intake has been associated in some studies with a lower risk of cognitive decline and dementia. Some clinical trials have also reported benefits in people with early cognitive impairment, although randomized trials have not established that omega-3 supplements prevent Alzheimer’s disease.
Many Western diets contain substantially more omega-6 than omega-3 fatty acids. Rather than trying to eliminate omega-6 fats, a reasonable goal is to make sure the diet provides adequate omega-3s, particularly EPA and DHA.
Fatty fish is an excellent source. For people who eat little fish or have low omega-3 intake, an omega-3 supplement may be a reasonable way to increase EPA and DHA, with possible benefits extending beyond brain health.
Bottom line: Omega-3s, particularly DHA, are important for health and may contribute to protecting the aging brain. They are a reasonable nutritional priority, while recognizing that supplementation has not been proven to prevent Alzheimer’s disease.
Magnesium is an essential mineral involved in energy production, blood-glucose regulation, blood pressure, nerve function, muscle function, and bone health. It also plays important roles in the brain.
Many Americans do not consume enough magnesium. National dietary surveys have found that nearly half consume less magnesium from food and beverages than the estimated average requirement, with older adults among the groups at greater risk of inadequate intake.
Low magnesium status has also been associated with Insulin Resistance and other metabolic and cardiovascular problems that themselves may affect brain health. Researchers are studying whether magnesium status may influence cognitive decline and dementia, although there is not yet good evidence that magnesium supplements prevent Alzheimer's disease.
Good food sources include nuts, seeds, legumes, leafy green vegetables, and other minimally processed foods. For people whose diets provide too little magnesium—or who have conditions or medications that increase magnesium loss—supplementation may be useful.
Bottom line: Getting adequate magnesium is worthwhile for general health and may also support healthy brain aging. The case for correcting inadequate intake is much stronger than the case for taking high doses specifically to prevent Alzheimer's disease.
Vitamin D is important for bone health, muscle function, immune function, and overall health, and maintaining adequate levels becomes particularly important as we age.
Low vitamin D levels have repeatedly been associated with a greater risk of cognitive decline and dementia. This does not prove that low vitamin D causes Alzheimer’s, and clinical trials have produced mixed results on whether supplementation improves cognition or prevents dementia.
The practical case for vitamin D is strongest when a person has low blood levels, limited sun exposure, or inadequate dietary intake. Measuring vitamin D can help determine whether supplementation is needed rather than assuming that more is better.
Vitamin D is available from fatty fish and fortified foods, but obtaining adequate amounts from food alone can be difficult for some people.
Bottom line: Maintaining adequate vitamin D is important for healthy aging and may also support brain health. Correcting a deficiency makes sense, but taking high doses specifically to prevent Alzheimer’s has not been proven beneficial.
Creatine is best known as a supplement for muscle strength and physical performance, but it also plays an important role in energy production in the brain. This makes it particularly interesting for healthy aging, when maintaining both muscle and cognitive function becomes increasingly important.
Creatine supplementation, especially when combined with resistance exercise, can help older adults maintain or improve muscle mass, strength, and physical function. Research is also examining whether increasing creatine availability in the brain can support memory and other aspects of cognition.
Recent studies and reviews have reported encouraging results for memory and attention, although the evidence is not yet strong enough to conclude that creatine prevents cognitive decline or Alzheimer’s disease.
Creatine occurs naturally in meat and fish, but supplementation can provide substantially more than is usually obtained from food. Creatine monohydrate is the form most extensively studied.
Bottom line: Creatine is one of the more interesting supplements for healthy aging because its benefits for muscle and physical function are relatively well established and its possible benefits for brain function are promising. It has not been shown to prevent Alzheimer’s disease.
Lithium is best known as a prescription treatment for bipolar disorder, but researchers have become increasingly interested in whether much lower doses might have neuroprotective effects.
Observational studies have found associations between greater exposure to trace amounts of lithium and lower rates of dementia. Laboratory research suggests several possible mechanisms, including effects on amyloid, tau, inflammation, and pathways involved in maintaining healthy brain cells.
Interest increased substantially after a 2025 study found unusually low lithium levels in the brains of people with mild cognitive impairment and Alzheimer’s disease. In mice, very low-dose lithium orotate reduced Alzheimer’s-like pathology and improved memory. Human evidence, however, remains preliminary. A recent two-year pilot trial of low-dose lithium carbonate in people with mild cognitive impairment produced some encouraging signals but did not demonstrate a clear overall cognitive benefit.
Lithium also deserves more caution than ordinary nutritional supplements. The kidney and thyroid risks associated with prescription lithium are well established, while the long-term risks of very low supplemental doses are less certain and may be considerably smaller. Lithium can also interact with certain medications. Lithium orotate supplements sold over the counter have not been established as a safe or effective way to prevent Alzheimer’s.
Bottom line: Low-dose lithium is one of the more intriguing experimental approaches to Alzheimer’s prevention, with enough biological and observational evidence to justify further clinical trials. It is not yet a proven preventive treatment and should not be self-prescribed for this purpose.
Metformin is an inexpensive, widely used medication for type 2 diabetes that improves Insulin Resistance and glucose regulation. Because Insulin Resistance and diabetes are associated with a greater risk of cognitive decline and dementia, researchers have become interested in whether metformin might also help protect the brain.
Several large observational studies have found lower rates of dementia among people with diabetes who take metformin, particularly with longer use. Other studies, however, have found little or no protective effect, making the overall evidence inconsistent.
Metformin is now being formally studied as a possible repurposed drug for Alzheimer’s prevention. The Metformin in Alzheimer Dementia Prevention (MAP) trial is testing extended-release metformin in people with mild cognitive impairment.
Metformin can also have disadvantages. Gastrointestinal side effects are common, and long-term use can reduce vitamin B12 levels, which is particularly relevant when considering brain health.
Bottom line: Metformin is an intriguing possibility for people with Insulin Resistance or other metabolic risk factors, where there may already be a medical reason to use it. Whether people without diabetes or metabolic dysfunction should take metformin specifically to prevent Alzheimer’s remains unproven.
GLP-1 drugs were developed to treat type 2 diabetes and are now also widely used for obesity. Medications such as semaglutide (Ozempic and Wegovy) can substantially improve blood-glucose control, reduce body weight, and lower cardiovascular risk in appropriate patients.
These effects have attracted considerable interest in Alzheimer’s research. Insulin Resistance, obesity, diabetes, and cardiovascular disease are all associated with greater risk of cognitive decline and dementia. Researchers are investigating whether GLP-1 drugs might reduce that risk by improving metabolic and vascular health and possibly through more direct effects on inflammation and the brain.
Large observational studies have reported lower rates of dementia among some people taking GLP-1 drugs, but observational studies cannot establish that the medications caused the reduction. Clinical trials are now providing more direct evidence, although the results so far do not establish GLP-1 drugs as Alzheimer’s-prevention medications.
These drugs also have potential side effects and are expensive, making the balance of benefits and risks very different for someone with obesity or diabetes than for a metabolically healthy person.
Bottom line: GLP-1 drugs are among the most interesting medications being investigated for their possible effects on brain health. For people who already have obesity, diabetes, or significant metabolic risk, their established health benefits may also prove beneficial to the brain. Using them specifically to prevent Alzheimer’s disease in otherwise healthy people is not currently established.
The relationship between cholesterol, cholesterol-lowering drugs, and Alzheimer’s disease is complicated and remains debated.
High LDL cholesterol—particularly in midlife—is associated with cardiovascular disease and has also been associated with a greater risk of dementia. Because vascular health and brain health are closely connected, some physicians believe that treating abnormal lipids may help reduce the risk of cognitive decline.
Statins are the most widely used cholesterol-lowering drugs. Many observational studies have found lower rates of dementia among statin users, and the overall evidence does not show that statins increase the risk of dementia. However, clinical trials have not established statins as a treatment specifically for preventing Alzheimer’s disease, and some physicians and researchers question whether aggressively lowering LDL is desirable for everyone when the primary goal is brain health.
Ezetimibe lowers cholesterol through a different mechanism, by reducing cholesterol absorption in the intestine. It is well established as a cholesterol-lowering medication, but researchers are also investigating whether it might have effects relevant to Alzheimer’s that extend beyond lowering LDL. Laboratory research has suggested possible effects on amyloid, tau, and cellular cleanup mechanisms, while observational human studies have reported associations with lower rates of Alzheimer’s. These findings are intriguing but preliminary and do not establish that ezetimibe prevents Alzheimer’s disease.
Other treatments, including PCSK9 inhibitors, can produce substantial reductions in LDL cholesterol. They are established for selected people at cardiovascular risk, but evidence that they independently prevent Alzheimer’s disease remains limited.
Bottom line: Protecting vascular health is an important part of protecting the aging brain, and treating abnormal lipids may be part of that strategy. Ezetimibe is particularly interesting because emerging research raises the possibility of brain effects beyond cholesterol lowering. But whether any cholesterol-lowering drug should be prescribed specifically to prevent Alzheimer’s remains uncertain.
PDE5 inhibitors—including tadalafil (Cialis) and sildenafil (Viagra)—are best known as treatments for erectile dysfunction. They work by enhancing nitric-oxide signaling and relaxing blood vessels, which improves blood flow.
Researchers have become interested in whether these drugs might have broader cardiovascular and brain-health benefits. Studies suggest that PDE5 inhibitors may improve endothelial function—the ability of blood vessels to dilate properly—and researchers are investigating their possible effects on vascular health, inflammation, and other processes involved in healthy aging.
Several large observational studies have also found lower rates of Alzheimer’s disease among men who use PDE5 inhibitors. Improved blood flow to the brain is one possible explanation, although other biological mechanisms are also being investigated.
These findings are intriguing but do not prove that Cialis or Viagra prevents Alzheimer’s. Much of the observational evidence comes from men treated for erectile dysfunction, so considerably less is known about possible Alzheimer’s benefits in women. The biological mechanisms being studied are not necessarily limited to men, but clinical trials in both men and women are needed.
PDE5 inhibitors are generally well tolerated but can cause headaches, flushing, indigestion, and low blood pressure. They can interact dangerously with nitrate medications.
Bottom line: PDE5 inhibitors are particularly interesting because their potential benefits may extend beyond erectile function to vascular and possibly brain health. Observational evidence linking their use with lower Alzheimer’s risk is encouraging, but taking Cialis or Viagra specifically to prevent Alzheimer’s is not yet an established treatment.
The growing interest in supplements and repurposed drugs for brain health can make it tempting to take many products “just in case.” But more is not necessarily better, and even supplements can have side effects or interact with medications.
A reasonable approach is to start with the fundamentals: a nutritious diet, exercise, good sleep, metabolic and cardiovascular health, and correction of identified nutritional deficiencies. Supplements can then be considered selectively when there is a plausible reason for taking them.
Some interventions discussed here—such as omega-3s, magnesium, vitamin D, and creatine—may have benefits for general health even if they are never shown to prevent Alzheimer’s. Repurposed medications require a different standard because their potential benefits must be weighed against their risks and should generally be considered with a physician.
Large, expensive supplement “stacks” and proprietary cognitive formulas deserve particular skepticism, especially when their ingredients or dosages are unclear.
Bottom line: The goal should not be to take as many potentially protective substances as possible. It should be to address individual risk factors and use supplements or medications selectively when the evidence and personal circumstances provide a reasonable rationale.
No supplement or repurposed drug has been proven to prevent Alzheimer’s disease in cognitively healthy people.
The strongest foundation for prevention remains addressing known and potentially modifiable risks, including Insulin Resistance, high blood pressure, abnormal lipids, physical inactivity, poor sleep, smoking, and nutritional deficiencies.
Omega-3s, magnesium, vitamin D, and creatine may have worthwhile benefits for general health even though their ability to prevent Alzheimer’s remains uncertain.
Low-dose lithium, metformin, GLP-1 drugs, ezetimibe, and PDE5 inhibitors are particularly interesting areas of research, but evidence for Alzheimer’s prevention remains preliminary.
Repurposed drugs may make the most sense when they also address an existing medical or metabolic risk factor, rather than being taken solely in hopes of preventing Alzheimer’s.
The goal should be selective, evidence-informed use, not accumulating a large supplement or medication stack.
Summarizes WHO’s 2026 recommendations for reducing dementia risk by addressing modifiable factors including physical inactivity, smoking, diet, social isolation, hearing loss, air pollution, hypertension, diabetes, and high cholesterol.
An overview of research on diet, vitamins, supplements, and other nutritional approaches being investigated for cognitive health and Alzheimer’s prevention.
Describes the 2025 research linking reduced lithium levels with Alzheimer’s disease and the experimental finding that very low-dose lithium improved Alzheimer’s-related abnormalities in mice.
A clinical trial investigating whether metformin can slow cognitive decline and biological changes associated with Alzheimer’s in people with mild cognitive impairment.
An overview of emerging research on Alzheimer’s prevention and the lifestyle, metabolic, and other potentially modifiable factors that may help protect brain health.
Dr. Norwitz discusses the 2025 Harvard research on lithium and Alzheimer’s disease, including why very low-dose lithium orotate produced particularly intriguing results in mice, and explains how the findings have influenced his own approach to brain health.
Dr. Norwitz discusses emerging research suggesting that ezetimibe may have effects relevant to Alzheimer’s disease that go beyond lowering cholesterol, including possible effects on amyloid, tau, and cellular cleanup mechanisms, while emphasizing that the human evidence remains preliminary.
Dr. Malik discusses research on tadalafil beyond erectile dysfunction, including its possible effects on cardiovascular health, blood flow, and healthy aging.
Dr. Brewer explains how tadalafil may improve endothelial function and arterial health through nitric-oxide signaling and discusses its possible use for vascular health.