By Rachel Burd

Researchers from universities in Tehran, Iran, led a clinical trial that tested the effect of probiotics on human cognition. 52 Alzheimer’s patients, ranging from 60 to 95 years of age, were studied. Probiotics are live bacteria that stimulate the proliferation of microorganisms, particularly those of the intestinal flora that are beneficial. Probiotics prevent infectious diarrheas, irritable bowel syndrome, allergies, and tooth decay. In murine studies, probiotics were shown to enhance learning abilities and memory function, as well as reduce anxiety, depression, and symptoms of Obsessive Compulsive Disorder among mice. The notion that probiotics could also improve human cognition is not new, as the microbiota-gut-brain axis is known to allow for signaling between the gastrointestinal tract and the central nervous system in humans.

This trial was controlled, randomized, and double-blind, meaning that neither the researchers nor the test subjects knew which test subjects were given the treatment and which were given the placebo. Half of the patients drank 200 mL of milk that had been enriched with Lactobacillus acidophilus, L. casei, L. fermentum, and Bifidobacterium bifidum, and this treated milk was consumed daily. The control group in this study drank untreated milk.

After 12 weeks, the researchers conducted MMSE (Mini-Mental State Examination) questionnaires, which ask patients to name objects, repeat phrases, count backwards from 100 by sevens, etc. The experimental group showed an increase in MMSE score from 8.7 to 10.6 out of a maximum score of 30.0. The control group did not show any increase. In addition to scoring higher on the MMSE, the experimental group showed a healthier lipid profile in their post-study blood samples, as well as lower insulin resistance and decreased activity of insulin-producing cells in the pancreas. These blood sample findings were consistent with previous studies on Alzheimer’s patients.

Although the patients in the experimental group still suffered from severe cognitive impairment, the increase in MMSE score demonstrates the positive impact of probiotics on human cognition. A longer treatment period is required to determine if the observed effect intensifies over time.


Frontiers. "Probiotics improve cognition in Alzheimer's patients." ScienceDaily. ScienceDaily, 10 November 2016. <>.