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Probiotics ‘aid memory in people with Alzheimer’s disease’


“Probiotics found in yoghurt and supplements could help improve thinking and memory for people with Alzheimer’s disease,” The Daily Telegraph reports after a small study found people given the bacterial supplement had improved scores on brain function tests.

Probiotics are live bacteria and yeasts promoted as having various health benefits, and are often added to yoghurt.

An Iranian research team gave people with severe Alzheimer’s disease a probiotic drink every day for 12 weeks, and then measured the changes in brain function test scores before and after the treatment.

They found small improvements after the probiotics were given compared with the placebo group, but it is unclear if these improvements were enough to be clinically useful or noticeable.

While the results are far from conclusive, they do add to a previous body of research that suggests there may be an association between gut health and brain function.

Exploring this association could lead to new insights and possible treatments for Alzheimer’s and other forms of dementia.

There are no known safety concerns about probiotics. But based on the small size and short-term nature of this study, more rigorous research would be required before probiotics could be recommended as an evidence-based treatment for people with Alzheimer’s disease.

Where did the story come from?

This Iranian study was carried out by researchers from Kashan University of Medical Sciences in Iran and was funded by a grant from the same university.

It was published in the peer-reviewed journal, Frontiers in Aging Neuroscience. This journal is open access, so the study is free to read online.

The UK media’s coverage of this study was generally accurate, although this is early research and its limitations were not fully discussed.

What kind of research was this?

This randomised controlled trial (RCT) looked at whether probiotic supplements help improve cognitive function in patients with Alzheimer’s disease.

It also investigated the effect of probiotics on biomarkers for inflammation and metabolism in the body.

Probiotics are often referred to as “good” or “friendly” bacteria, and are found in yoghurts and other dairy products.

Although probiotics have traditionally been recommended for people with gut conditions such as irritable bowel syndrome (IBS), recent research has shown they may benefit the brain, too.

This is because there may be a link between the gut and the brain along what’s known as the micro biota-gut-brain axis.

This axis is a biochemical signalling pathway that runs between the brain and the digestive system. But its full role in terms of health outcomes is thought by many to not be fully understood.

Double-blind randomised controlled trials like this one are thought to be the gold standard when it comes to investigating a potential association between an exposure and an outcome – in this case, between probiotic supplements and changes in cognitive function.

What did the research involve?

This 12-week trial recruited 60 patients with Alzheimer’s disease with a mean age of 80. The participants were all matched for disease severity based on gender, age and body mass index (BMI).

They were then randomly assigned to two treatment groups (30 participants in each): the control group received plain milk, while the intervention group received probiotic milk (200ml a day).

The probiotic drink contained the bacterial strains Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum and Lactobacillus fermentum.

The patients’ cognitive function was measured before and after the 12-week trial using a Mini-Mental State Examination (MMSE). This scale is a 30-point questionnaire used extensively to measure cognitive impairment.

The test takes about 10 minutes to complete and assesses cognitive – or thinking – abilities such as attention, calculation, recall, language, and the ability to follow simple commands.

One example question is to ask people to count backwards from 100 in sevens. Any score greater than or equal to 24 points out of 30 indicates normal cognition.

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.

During the study, four patients from each treatment group died from old age. A total of 52 patients went on to complete the study. The data from these 52 patients was analysed and the findings were compared between the two treatment groups.

What were the basic results?

Overall, the 12-week treatment with probiotic supplements resulted in an improvement in the MMSE score of +27.9%, compared with a decrease of -5.03% in the control group.

In absolute terms this means that the control group deteriorated from 8.47 to 8.00, remaining severely impaired on the 30-point scale. Those taking probiotics improved from 8.67 to 10.57.

Although the difference was statistically significant, it is still a small change and suggests that even after taking probiotics everyone remained severely cognitively impaired.

The probiotic treatment also had a positive influence on a range of other blood markers that were of interest to the researchers.

However, changes in biomarker levels for oxidative stress, fasting plasma glucose (a marker of insulin sensitivity) and other lipid (fat) profiles remained insignificant.

It is not clear if these have a bearing on the development of Alzheimer’s and how any link between them and drinking probiotics might be acting.

How did the researchers interpret the results?

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.”


This randomised controlled trial looked at whether probiotic supplements help improve cognitive function in patients with Alzheimer’s disease over 12 weeks.

It also investigated the effect of probiotics on biomarkers for inflammation and metabolism in the body.

It found treatment with probiotic supplements resulted in a small improvement in cognitive function compared with the control group.

But everyone remained severely cognitively impaired, and it’s not clear if the change in score was clinically important in terms of function.

Although these are interesting findings, there are a few things to bear in mind:

  • This was a small trial involving 60 people. This intervention would need to be tested on a larger sample size to confirm the findings, as it’s still possible that the change observed is a chance finding.
  • The participants were mainly female – only 12 male patients were involved – and everyone had severe dementia at the start of the study, so it’s unclear whether probiotics are able to prevent dementia in the general population.
  • The trial was conducted for 12 weeks. As Alzheimer’s is a progressive disease, it would be beneficial to monitor the long-term effects of probiotics in patients with Alzheimer’s disease to know whether the improvement in cognitive function would last longer than three months.
  • The participants in the trial were an average age of 80. It would be interesting to see if the same effect was observed in patients at an earlier stage of Alzheimer’s disease.

Dietary advice for people with Alzheimer’s disease is the same for most other people – to eat a healthy, balanced diet.

Read more advice about caring for someone with Alzheimer’s or other forms of dementia.

Analysis by Bazian. Edited by NHS ChoicesFollow NHS Choices on TwitterJoin the Healthy Evidence forum.


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