Could Probiotics Aid Alzheimer’s Symptoms?

Joanna Scott-Lutyens BA (Hons) DipION

Studies1 which looked into the effects of probiotics for Alzheimer’s found that probiotic bacteria improved cognitive function in participants with this disease.

Within this article:

Mature hands holding hands
Alzheimer's disease is the most common type of dementia, affecting 62% of those diagnosed.

Traditionally probiotics have been associated with gut health only. However, there has been growing evidence that the gut and brain are linked by the gut-brain axis. So far the emphasis has been on the connection between gut bacteria and neurotransmitter production leading to an influence on stressanxiety, and depression. An Iranian study1 carried out by researchers from Kashan University of Medical Sciences now leads to a fascinating and promising idea that, there may also be a connection between gut flora and Alzheimer’s.

Probiotics for Alzheimer's

This randomised, double-blind, and controlled clinical trial ran over a 12-week period and involved 52 patients with Alzheimer's disease with a mean age of 80. The participants were randomly assigned into two treatment groups, one receiving 200ml of probiotic milk daily and the other being a control group who were given normal milk. The probiotic drink contained the bacterial species Lactobacillus acidophilusLactobacillus caseiBifidobacterium bifidum and Lactobacillus fermentum at approximately 400 billion live cultures per species.

The patients' cognitive function was measured before and after the 12-week trial using something called a Mini-Mental State Examination (MMSE). This is a 30-point questionnaire commonly used to measure cognitive impairment. This test assesses cognitive and thinking abilities such as attention, calculation, recall, language, and the ability to follow simple commands.

Additionally, blood samples were also collected to assess levels of biomarkers for oxidative stress, which is an indicator of cell damage, as well as inflammation and metabolic profiles.

The results of this study were that overall the 12-week supplementation with probiotics resulted in an improvement of 27.9% in the MMSE score, compared to a decrease of 5.03% in the control group. This is a statistically significant result even if small. The probiotic treatment also had a positive effect on a range of other blood markers including MDA, a marker for oxidative stress, hs-CRP which is an inflammatory marker and additionally to this, blood triglyceride levels. However, changes to other oxidative stress and inflammatory markers were not statistically significant.

The researchers concluded that,

"The current study demonstrated that the probiotic administration for 12 weeks has favourable effects on MMSE score, MDA, hs-CRP, markers of insulin metabolism and triglycerides levels of the AD patients; however, the changes in other biomarkers of oxidative stress and inflammation, FPG and other lipid profiles are negligible."

Nerve image showing gut brain connection
The gut-brain connection is a fast growing area of research

What does this mean for those with Alzheimer’s?

This is a really interesting trial. It shows, statistically, that probiotics help with the symptoms of Alzheimer’s which is encouraging for anyone wanting to address this disease naturally. However, it is important to keep this study in context, in the sense that it was a relatively small study, with participants who had the mean age of 80 and ran for only a relatively short period of time. The general consensus is that Alzheimer’s is not curable, or reversible and that it is progressive. It would therefore be fascinating to see a trial using not only a larger number of participants but also one running for a longer period of time to see if probiotics could affect the progression of this disease.

Additionally, it would be interesting to investigate the use of probiotics with younger participants, and at an earlier stage of Alzheimer’s to see it this intervention could actually prevent, or halt the development of this disease.

Dr Rosa Sancho, head of research at Alzheimer's Research UK, said:

"The brain is often viewed as being separate from the rest of the body but scientists are understanding more about how changes in the body can impact upon the brain too. This new study raises interesting questions about the link between the gut and the brain, and their association with Alzheimer's disease. The improvements in memory and thinking, seen in people with Alzheimer's disease in this study will need to be repeated in much larger studies before we can understand the real benefits of probiotics for the brain."

The fact that the trial also showed benefits to levels of cholesterol in the blood as well as other health markers should not be forgotten, as these have an influence on how we age. Interestingly, a previous study2 found that gut bacteria played an important part in protecting the blood-brain barrier and could, therefore, have an influence on protecting the brain’s delicate structure from damage potentially influencing other brain related dieases. It’s fascinating to see the way in which probiotics appear to extend their influence in us both physically and mentally. And although, as Dr Sancho says, more research is needed in this area, it is indeed an exciting advance in knowledge in this area.

Additionally, there has been recent research into a genetic compentent linking gut health and Alzheimer's3. It was found that there is a distinct genetic overlap between Alzheimer's disease and certain gastrointestinal disease, including IBS, GERD and diverticulosis. Another study found that proinflammatory gut microbiota has the potential to promote AD development through interaction with APOE genotype6.

If you found this information about probiotics for Alzheimer's interesting, read our blog post by Kerry over in the Probiotics Learning Lab: Gut-brain axis


  1. Akbari Elmira et al., (2016) Effect of Probiotic Supplementation on Cognitive Function and Metabolic Status in Alzheimer's Disease: A Randomized, Double-Blind and Controlled Trial. Frontiers in Aging Neuroscience vol 8 DOI=10.3389/fnagi.2016.00256
  2. Braniste, V. et al.,(2014) ''Blood-Brain Barrier: The gut microbiota influences blood-brain barrier permeability in mice''. Science translational medicine, Volume 6, Issue 263, doi: 10.1126/scitranslmed.3009759
  3. Adewuyi EO, O'Brien EK, Nyholt DR, Porter T, Laws SM. A large-scale genome-wide cross-trait analysis reveals shared genetic architecture between Alzheimer's disease and gastrointestinal tract disorders. Commun Biol. 2022;5(1):691. doi:10.1038/s42003-022-03607-2
  4. Fatma Nur Güleç, Ismail A. Elhaty (2021) Impact of Diet and Intestinal Microbiome on Neurodegenerative Diseases. Journal of Cardiovascular Disease Research, VOL 12, ISSUE 03.
  5. S Shi et al., (2023) Probiotic Bifidobacterium longum BB68S Improves Cognitive Functions in Healthy Older Adults: an RCT. Nutrients, 15(1): 51.
  6. Cammann D et al., (2023) Genetic correlations between Alzheimer’s disease and gut microbiome genera. Scientific reports, 13: 5258.