Cognitive impairment, dementia, and Alzheimer’s disease (AD), can be a nightmare scenario for many, especially as they get older.
And while many view these declines as an inevitable or normal part of aging, what if there was something we could do to either prevent these declines or at least lessen their impact, helping those suffering from them to live a more normal and enjoyable life?
And what if that something was probiotics?
We’ve already shown the connection between probiotics and healthy body weight as well as their positive impact on IBS. And, perhaps by the time you are reading this article we’ve discussed even more. But is it possible that probiotic supplementation, an act that is intended primarily to support gut health, could have farther-reaching effects that impact how our brains function?
The answer is yes.
The science behind probiotics and cognitive decline
I did a deep dive for meta-analyses from around the world to determine what the scientific research community was finding about probiotics.
In doing so, I discovered boatloads of published studies examining probiotics’ impact on cognitive decline, dementia, and AD.
So I checked them out to see what they had to say, good or bad.
And the good news is, the good came out on top.
I analyzed 15 meta-analyses for you, all published since 2020. Here is what I found.
The Good
A meta-analysis of randomized controlled trials published in the journal Medicina Clinica in 2024 found that probiotics improved global cognitive function, recall, attention, and visuospatial/constructional cognitive domain among patients with Alzheimer’s disease or mild cognitive impairment. [1]
A meta-analysis published in Journal of Health, Population, and Nutrition in 2025 found that probiotic supplementation improved cognitive function in study subjects with Alzheimer’s disease as well as those subjects with mild cognitive impairment. They believe these benefits were likely achieved through the probiotics’ effect on reducing inflammation and oxidative stress as well as through improving insulin sensitivity. [2]
(Here we see insulin sensitivity and inflammation popping up again. The more you read through the scientific literature, the more you see these two continue to pop up, even in places where you might not expect it. You might want to learn about their connection to weight loss here.)
A meta-analysis published in PLoS One in 2025 found that “probiotics were effective in enhancing cognitive function among patients with cognitive impairment”, with single-strain interventions lasting less than or equal to 12 weeks in duration showing the most pronounced effect. [3]
A meta-analysis published in Progress in Neuro-psychopharmacology & Biological Psychiatry in 2021 found that, in human studies analyzed, “the administration of probiotics improved general cognitive function after the treatment period.” In animal studies, they noticed improvement in spatial/non-spatial learning. Results also showed improvements in the levels of brain-derived neurotrophic factor, which is an improvement in inflammatory profile. [4]
(Here we see health improvements connected to inflammation improvements once again.)
An umbrella review of meta-analyses published in European Journal of Pharmacology in 2025 found that probiotic treatment significantly enhanced cognitive function in patients, although they also noted that the quality of the existing evidence is “insufficient to provide strong support” and that more rigorous future research is needed to “further validate the efficacy of probiotic therapy on cognitive function of patients with cognitive dysfunction.” [5]
A very robust meta-analysis published in Journal of Food Science in 2025 that included only double-blind RCTs studying patients 65 or older with diagnosed Alzheimer’s disease found that probiotic supplementation resulted in significant cognitive improvement when compared to placebo. [6]
A meta-analysis published in the journal Nutrition Reviews in 2023 found that probiotic supplementation showed a significant effect on cognition in studies on those with Alzheimer’s disease or cognitive impairment. They also found the most effectiveness when probiotics were administered for greater than 12 weeks. [7]
A meta-analysis published in the journal General Hospital Psychiatry in 2025 found that probiotic supplementation significantly improved cognitive function compared to placebo. Improvements were most pronounced in interventions lasting at least 12 weeks. [8]
A meta-analysis published in the journal Geriatric Nursing in 2023 found that probiotic supplementation among older adults with cognitive impairment exhibited a positive impact on cognitive symptoms, in particular memory and overall cognitive function. They also found improvements in oxidative stress levels, total antioxidant capacity, malondialdehyde, and glutathione. They did not find improvements in psychological symptoms, however. [9]
(And now we see antioxidants popping up. Positive changes in antioxidant status seems to be found when improving a myriad of health ailments as well.)
A meta-analysis published in the journal Neurological Sciences in 2023 found that, in 9 of 10 studies analyzed, cognitive function was improved significantly after probiotic supplementation. The only outlier was a study that included severe Alzheimer’s disease. The researchers noted that “most studies involving AD, MCI (mild cognitive impairment), or healthy older adults showed cognitive improvement in subjects treated with probiotics for 12-24 weeks.” [10]
A meta-analysis published in the journal BMC Complementary Medicine and Therapies in 2025 found that “probiotics improved cognitive function, especially after 12 weeks of supplementation, using the MoCA (Montreal Cognitive Assessment) test.” They also noted, however, that the certainty of evidence was low and further rigorous trials are were warranted. [11]
The iffy and the inconclusive
There have been some studies that have not been nearly so glowing. We need to take those into account as well.
A meta-analysis published in the journal Neuroscience and Biobehavioral Reviews in 2020 found no significant effect for probiotic intervention on cognition. The researchers noted that this result could have been due to the fact there was a “limited number of small and short-term studies as well clinical heterogeneity relating to the population, cognitive tests, and intervention” at the time of the analysis. [12]
A meta-analysis of randomized controlled trials published in the journal Nutrition Reviews in 2021 found that subjects with Alzheimer’s disease had no beneficial effect on cognitive function after receiving Lactobacillus and Bifidobacterium strains. However, they did note that there was very low certainty of evidence. [13]
A meta-analysis published in the journal Aging & Mental Health in 2022 did not find significant alterations in the cognitive function of elderly research subjects via probiotic supplementation. They did find significant increases in levels of antioxidant activity and total glutathione, however, and noted that the results observed may have been due to heterogeneity across the studies analyzed. [14]
What does all this mean for us?
It seems obvious that preponderance of the evidence is in favor of probiotics having a positive effect on our cognition.
While there are not yet studies proving that probiotics, either individual strains or combinations, can outright prevent cognitive decline entirely or heal it entirely, it has plenty of evidence to show it could be a very valuable tool in our toolbox. Perhaps even one that could contribute to living a much better life.
We also know that many of the studies found that a duration of 12 weeks or longer seemed to show the most effectiveness. That is not to say that there cannot be improvements had prior to 12 weeks. What it does say is that, like many natural remedies, patience is key.
Remember, it usually takes a long time to reach a state of dis-ease, so a few weeks or months to see true improvement is not actually all that long. Patience is important.
Now, very importantly, there are some things we do not know.
For one, there is no clear answer, from these studies at least, as to which strain or strains might be the most effective and in what dosages. Every probiotic on the market is different and some may be more beneficial than others.
And while an effective probiotic supplement may be helpful, the results of these studies give us an indication that the overall state of our gut microbiome may also be at play. Meaning, maintaining a healthy and diverse microbiome may be very important to help prevent or even help treat cognitive decline.
And to maintain a healthy and diverse gut microbiome, we need to make sure that we reduce or eliminating processed foods and simple sugars (bad bacteria love those) and instead increase a variety of whole foods. Especially a variety of foods with high amounts of antioxidants, phytonutrients, and fiber, such as colorful fruits and vegetables.
Different gut microbes love fiber and different types of phytochemicals found in many plant foods. So consuming a variety of healthy and safe fruits and vegetables can be very beneficial in feeding our healthy gut microbiome and maintaining a healthy diversity of microbes, each doing their own part to help us get and stay healthy.
Closing thoughts
Probiotics could be a great tool, with more and more benefits being found all the time. But they may not be for everybody. Some people may not react well to them. That is why it is important that you work with your licensed healthcare practitioner to determine what is safe and appropriate for you. The information presented here is just for informational purposes only.
Secondly, remember to listen to your body. It’s okay to ease off of probiotics if you don’t feel right. There are other ways to help create a healthy microbiome, as we’ve discussed already.
By getting rid of processed foods and simple sugars, you are stopping the food source of bad bacteria before they can get it and grow. And by consuming a wide variety of colorful fruits and vegetables with all their antioxidants, phytonutrients, and fiber, you are feeding the good bacteria what they need to thrive instead. So you have more ways to help create a healthy gut than by supplements alone.
As is usually the case.
So be sure to talk to your licensed healthcare practitioner to find out what is right for you, and all the best to you as you retake your good health!
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References
[1] https://pubmed.ncbi.nlm.nih.gov/38641508/
[2] https://pubmed.ncbi.nlm.nih.gov/40200373/
[3] https://pubmed.ncbi.nlm.nih.gov/40315198/
[4] https://pubmed.ncbi.nlm.nih.gov/33285265/
[5] https://pubmed.ncbi.nlm.nih.gov/39914784/
[6] https://pubmed.ncbi.nlm.nih.gov/40709497/
[7] https://pubmed.ncbi.nlm.nih.gov/36629438/
[8] https://pubmed.ncbi.nlm.nih.gov/41237466/
[9] https://pubmed.ncbi.nlm.nih.gov/37788563/
[10] https://pubmed.ncbi.nlm.nih.gov/36529793/
[11] https://pubmed.ncbi.nlm.nih.gov/41291638/
[12] https://pubmed.ncbi.nlm.nih.gov/32860802/
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