A new study found that a daily dose of Lactobacillus and bifidobacterium bacteria, taken over 12 weeks, was enough to make moderate improvements in patients' scores for various mental tasks.
Probiotics are found naturally in fermented foods, such as yogurt, fermented soy products, sauerkraut, and kefir. They are also available in the form of high-dose probiotic “shot” drinks, freeze-dried powders, capsules, and tablets.
These “friendly” bacteria can help balance the levels of microorganisms in the intestines and drive down numbers of harmful bacteria.
Research into probiotics has shown they can help protect against certain conditions, including diarrhea, inflammatory bowel disease, allergies, and tooth decay. However, scientists have also pondered whether they might also boost brain function. For instance, trials with mice have shown that probiotics improve learning and memory and also reduce anxiety and depression.
The latest study by a team from Kashan University of Medical Sciences and Islamic Azad University in Iran claims to be the first to demonstrate this effect with people.
The group was split into two, with one-half receiving 200 milliliters (about 7 ounces) of milk each day that had been enriched with four types of probiotics. These were Lactobacillus acidophilus, L. casei, L. fermentum and Bifidobacterium bifidum.
People in the second group were just given plain milk.
All the participants completed a test that measures different mental abilities, including a person's memory, attention, and language skills. The highest attainable score in the test is 30.
The researchers found that during the study, the average score among the volunteers taking the probiotics rose from 8.7 to 10.6. In contrast, those who had been given ordinary milk saw a fall in their score from 8.5 to 8.0.
They acknowledge that all the participants, no matter which group they were in, scored poorly for memory and thinking skills. But they say the difference in results between the two groups was significant.
The researchers say they think that metabolic changes might be responsible for the difference in the groups. For instance, those who were given probiotics also showed improvements in insulin metabolism and lipid profiles.
Linking the Gut and the Brain
Professor Mahmoud Salami from Kashan University, author of the study, says in a statement: "In a previous study, we showed that probiotic treatment improves the impaired spatial learning and memory in diabetic rats, but this is the first time that probiotic supplementation has been shown to benefit cognition in cognitively impaired humans."
Rosa Sancho, head of research at Alzheimer’s Research UK, says: "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 links 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.
"We don’t fully understand how changes in the gut could be affecting the brain, and Alzheimer’s Research UK is funding research in this area to improve our understanding of this link."