For those over 60, it’s quite likely that a pill organizer has found a place on the kitchen counter. Research indicates that around 76% of adults in this age group take at least one dietary supplement, with over half consuming two or more, as reported by the Centers for Disease Control and Prevention’s National Center for Health Statistics.
Following multivitamins, vitamin D and omega-3 supplements, such as fish oil, rank among the most commonly used in the U.S. An earlier report from the NCHS pointed this out. Add in glucosamine—which many swear by for joint issues—and you’ve got a lineup of what many consider to be the friendly faces in the supplement aisle.
However, scientists are now raising a rather uncomfortable question: Could some of these pills actually be detrimental to the very brain you’re aiming to safeguard? A recent article in The Washington Post shed light on new research that might make you reconsider.
But before you go tossing your supplements, it’s crucial to clarify what this research entails. Most of the red flags stem from studies that observe trends instead of establishing direct cause and effect. Additionally, some findings contradict one another.
Yet, there is one fact that should worry anyone shelling out cash for these products: The Food and Drug Administration does not evaluate supplements for safety before they are made available to consumers.
In simpler terms, companies are not required to demonstrate that their pills genuinely safeguard your brain—or worse, that they don’t harm it.
1. Fish oil: A billion-dollar habit with a brain problem
Fish oil has become a massive market in the U.S., raking in over a billion dollars annually. A significant reason for its popularity is the hope that the omega-3 fatty acids found in fish oil will contribute to mental sharpness.
Researchers from USC conducted a rigorous study to assess this hope. They recruited 365 participants aged 55 to 80 who infrequently consumed fish and were at a higher risk for Alzheimer’s disease.
Participants were randomly divided to receive either a placebo or a daily dose of 2,000 milligrams of DHA—a primary omega-3 in fish oil.
While the supplements did increase DHA levels in the brain fluids by an average of 17% after six months, they did not translate into any cognitive improvements. After two years, those taking fish oil had no better outcomes from memory and thinking tests compared to the placebo group. Moreover, brain scans revealed no signs of protection against the shrinkage of the hippocampus, which plays a key role in memory.
Dr. Hussein Yassine, who led the study, stated that fish oil supplements “do not appear to protect brain health.”
This doesn’t really come as a shock for those familiar with reports that heavily marketed memory supplements often fall short. However, wasting money is one concern; two additional studies indicate potential harm.
This past spring, researchers reviewed data from the Alzheimer’s Disease Neuroimaging Initiative, which tracks memory and brain scans in older adults. They found that 273 omega-3 supplement users exhibited a quicker decline in memory and cognitive tests over approximately five years compared to 546 non-users.
While this raises alarms, it’s important to note that this was an observational study, so it only identified a pattern rather than confirming direct causation. Interestingly, an earlier examination of the same data suggested omega-3 usage could actually lower the risk of Alzheimer’s.
The second troubling study, conducted by the Medical University of South Carolina, suggested that EPA, another key omega-3, may inhibit the brain’s ability to heal after mild head injuries in mice.
They observed similar results in human brain blood vessels in laboratory settings. Despite this, lead investigator Onder Albayram cautioned against jumping to conclusions about discontinuing fish oil.
It’s also worth keeping balance in mind. If you tend to be unsteady, you might want to be cautious; falls are a leading cause of traumatic brain injuries and account for about 4.5 million emergency room visits yearly among older adults, according to the CDC.
If that resonates with you, investing in some home modifications might be wiser than picking up another bottle of capsules.
2. Glucosamine: A joint pill with a brain question mark
We’ve touched on glucosamine before, but it bears repeating here. It’s a popular choice for seniors dealing with joint pain.
Researchers from the University of Florida employed artificial intelligence to analyze patient records from 2012 to 2024. They found that among those with mild cognitive impairment, glucosamine users had a 25% higher likelihood of progressing to dementia.
For patients already diagnosed with dementia, those taking glucosamine faced a 25% increased risk of mortality.
Because glucosamine can enter the brain, researchers suspect it might exacerbate processes already disrupted in Alzheimer’s patients.
Lead author Ramon Sun cautioned that many individuals with dementia may be taking a supplement that “could be making their disease progression worse.”
It’s important to mention that this finding reflects an association, not definitive proof, and further studies—particularly clinical trials—are necessary. Notably, glucosamine didn’t seem to increase mortality risk among those with mild cognitive impairment, indicating the greatest concern arises once dementia is evident.
3. Vitamin D: The scariest finding is also the shakiest
Vitamin D is well-known for its role in helping the body absorb calcium and maintaining strong bones. So, when there are indications that it might be linked to dementia, it’s understandable if that raises some eyebrows.
This alarm primarily arises from a 2022 study by researchers in Taiwan. They observed that older adults without dementia who took vitamin D3 for over 146 days out of the year were 1.8 times more likely to receive a dementia diagnosis. Among individuals already diagnosed with dementia, long-term users had over double the risk of death.
That sounds alarming. Yet, the scientific community, including those at Oregon State University’s Linus Pauling Institute, has contested these claims. They argue that the Taiwanese data may have actually been tracking calcitriol, a medication used for certain kidney or parathyroid conditions—different from the vitamin D typically sold in stores—and these patients may have already had pre-existing health issues.
Meanwhile, a more robust study suggests the opposite. A Finnish trial published in 2025, involving nearly 2,500 older adults, examined the effects of daily doses of either a placebo or 1,600 to 3,200 international units of vitamin D3 over a period of up to five years.
Results showed that vitamin D did not influence dementia rates at either dosage. One detail to note is that most participants were not deficient in vitamin D to start with.
In August, a smaller Emory University study involving 54 individuals with sleep and memory issues linked high doses of 5,000 IU a day or more to improved scores on cognitive assessments. However, senior author Victoria Pak stated that it’s premature to recommend such high dosages.
So, what’s the real concern surrounding vitamin D? The risk of taking too much. The National Institutes of Health advises that the maximum daily intake for adults should not exceed 4,000 IU, encompassing both food and supplements.
High doses could also interfere with medications, potentially reducing the effectiveness of cholesterol-lowering statins or, when combined with certain diuretics, leading to elevated blood calcium levels.
Regarding who could benefit from additional supplementation, the Endocrine Society suggests that healthy adults under 75 should stick to the recommended daily amount, while those 75 and over might consider higher doses due to a potential reduction in mortality risk.
What to do if these pills are in your cabinet
First and foremost, don’t stop taking any medications prescribed by your doctor. Some individuals genuinely need vitamin D supplements, and others may be advised to take omega-3s for medical reasons. These are conversations to have with your healthcare provider, not topics for sensational headlines.
Second, if you or someone you care about is experiencing memory issues, bring all supplement bottles to your next medical appointment. Ask about glucosamine specifically, along with any fish oil or high-dose vitamin D you may be using without professional guidance.
Third, take a moment to assess the cost. Suppose your supplement routine costs around $30 a month—that’s $360 a year, or $3,600 over a decade. If leading research indicates that a particular pill isn’t benefiting your brain, those funds could be redirected to more effective alternatives.
So, what does help? U.S. News recently noted that many health experts agree that maintaining mental sharpness post-60 isn’t just about supplements. It’s more about regular physical activity and nutritious foods, with quality sleep following closely behind.
If you’re looking for omega-3s, it might be best to consume them through your diet rather than capsules. Researchers from USC believe that omega-3s may have a more positive impact as part of a Mediterranean-style diet, rather than in supplement form.
Lastly, keep things in perspective. Not long ago, we reported on research suggesting omega-3s and vitamin D supplements might slightly slow biological aging. The science surrounding supplements changes frequently, which is why it’s wise to be cautious about investing in promises.
The bottom line
The supplement industry offers a false sense of certainty in a bottle, and the science doesn’t necessarily support that confidence.
No one has definitively shown that these three pills are harming aging brains, but there’s no concrete proof that they’re protecting them either. Ultimately, it seems you might be the one funding this ongoing experiment.
