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Annual Microbiome Issue: Gut-Brain Axis

25 August 2016 - Posted by Kathryn Kos

Diet and the Effect on Memory, Gut Microbiota and Markers of Brain Inflammation and Plasticity1


Researchers look at the long-term effects of a high saturated fat and sugar diet on gut microbiota, neuroinflammation and neuroplasticity markers. Rats were given a 2 week diet of either a control, sugar, saturated fatty acid, or polyunsaturated fatty acid diet. There were group differences in the amount of energy derived from protein, fat complex, and simple carbohydrates.

In a hospitalized intervention trial of children with obesity and Prader-Willi syndrome, the diet rich in non-digestible carbohydrates induced significant weight-loss, as well as structural changes within the gut microbiota. They found that children who were genetically obese with Pader-Willi syndrome shared a similar gut microbiome with children who have diet related obesity.


  • Exposure of rats to a diet high in saturated fatty acids or sugar for less than 2 weeks impaired hippocampal-dependent place recognition memory, compared to control and polyunsaturated fatty acid fed rats.
  • There was no effect of diet on perirhinal-dependent object relation memory.
  • Hippocampal and hypothalamic inflammatory markers were not substantially affected by the diets and there was no change in neuroplasticity markers.
  • Each of the diets significantly altered the microbial composition in different way.
  • Both the saturated fatty acid and sugar groups were impaired on place recognition, but not object recognition memory, compared to control and polyunsaturated fatty acid groups after 8-9 days of diet.
  • In less than 2 weeks the researchers did not find substantial changes in inflammation related genes or neuroplasticity markers in the hippocampus or hypothalamus.
  • Each of the diets significantly altered the fecal microbial composition in distinct ways, but did not change the number of species or diversity.
  • Researchers found that object recognition memory was related to the microbiota PC1, while place recognition memory was related to microbiota PC3.

Key Message:

The control rats derived more energy from protein than the other groups, and the sugar rats consumed more than the saturated fatty acid and polyunsaturated fatty acid groups. The saturated fatty acid and polyunsaturated fatty acid groups derived the same amount of energy from fat, which was more than the sugar and the control groups. The control rats derived more energy from simple carbohydrates than the saturated fatty acid and polyunsaturated rat groups.

Key Points:

  • Even after short exposure to dietary changes high in sugar and saturated fat, the gut microbiota composition changes dramatically and may affect certain aspects of memory.
  • Microbiota may have a more crucial role of metabolizing and producing neuroactive compounds.
  • Further research around the relationship between poor diet, microbial changes and memory deficits may be warranted.

The Effect of Multi-species Probiotics on Cognitive Reactivity to Sad Mood2


The gut and brain are connected through bi-directional communication via neural, endocrine, and immune pathways. Researchers test recent insights on the role of probiotics and the gut-brain connection. Their goal was to determine if there was an effect from probiotic supplementation on cognitive function and depression. A multi-species probiotic was tested.

The study design was a triple-blind, placebo controlled, randomized, pre- and post-intervention assessment design. For the study, 20 healthy participants without current mood disorder were given 4 weeks of probiotic food-supplements with multi-species probiotics, while 20 control participants received a placebo during that same period. The healthy participants were young adults, no cardiac, renal, or hepatic conditions, no
allergies, or prescribed medications.

Researchers did a pre- and post-study intervention called a LEIDS self-report questionnaire, which assessed the participant’s cognitive reactivity to sad mood. There were six scales measuring: aggression, hopelessness, acceptance/coping, control/perfectionism, risk aversion, and rumination.


  • Compared to participants who received the placebo, participants who received the intervention of multi-species probiotics showed a significantly reduced overall cognitive reactivity to sad mood, with reduced rumination and aggressive thoughts.

Key Points:

  • Multi-strain probiotic supplementation may help reduce negative thoughts associated with sad moods.
  • Probiotic supplementation may be a potential strategy to help with depression.

Gastrointestinal Symptoms and Behavioral Problems in Preschoolers with Autism Spectrum Disorder3


Gastrointestinal symptoms are often reported in children with Autism Spectrum Disorder (ASD). The aim of this particular research was to explore the type and the prevalence of GI symptoms in ASD patients and typical development (TD) controls, and to investigate their possible association with behavioral problems. 230 preschoolers partcipated in this study. Specifically, four groups of children were evaluated: ASD individuals suffering from GI symptoms (ASD/GI+), ASD subjects without GI symptoms (ASD/GI-), TD peers with (TD/GI+) and without (TD/GI-) GI symptoms. Parental report of behavioral problems and GI symptoms were assessed through the Child Behavior Checklist.


  • A significant higher percentage of ASD (37.4%) versus TD (14.8%) with GI symptoms was observed.
  • ‘Constipated’ and ‘Not-Eat’ were the most frequent GI symptoms both in ASD and in TD groups, but they were evaluated as more severe in ASD patents.
  • ASD/GI+ children had more anxiety problems, somatic complaints, externalizing and total problems than ASD/GI-individuals.
  • TD/GI+ did not show more behavioral problems than TD/GI-.

Key Points:

  • Digestive health is an important factor to address for ASD children with anxiety and/or other behavioral problems.

  1. Beilharz, J, Kaakoush, NO, & Manium J et al. (2016). The effect of short-term exposure to energy-matched diets enriched in fat or sugar on memory, gut microbiota and markers of brain inflammation and plasticity. Brain, Behavior, and Immunity. pii: S0889-1591(16)30345-2. doi: 10.1016/j.bbi.2016.07.151. Available at: http://www.sciencedirect.com/science/article/pii/S0889159116303452 Accessed August 25, 2016 []
  2. Steenbergen L, Sellaro R, & Hemert SV et al. (2015). A randomized controlled trial to test the effect of multi-species probiotics on cognitive reactivity to sad mood. Brain, Behavior and Immunity. J Infect. Vol. 48 pp 258-64. Doi 10 1016/j.bbi2015.04.033 Available at: http://www.ncbi.nlm.nih.gov/pubmed/25862297 Accessed August 25, 2016 []
  3. Fulceri F, Morelli M & Santocchi E et al. (2016). Gastrointestinal symptoms and behavioral problems in preschoolers with Autism Spectrum Disorder. Digestive and Liver Disease. Vol. 48, Issue 3 pp 248-54. htp://dx.doi.org/10.1016/j.dld.2015.11.026 Available at: http://www.ncbi.nlm.nih.gov/pubmed/26748423 Accessed August 25, 2016 []

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