Press release: High-Fat Diet Alters Behavior And Produces Signs Of Brain Inflammation, Elsevier, 26 March 2015
Non-obese mice “received a transplant of gut microbiota from donor mice that had been fed either a high-fat diet or control diet,” and:
The animals who received the microbiota shaped by a high-fat diet showed multiple disruptions in behavior, including increased anxiety, impaired memory, and repetitive behaviors. Further, they showed many detrimental effects in the body, including increased intestinal permeability and markers of inflammation. Signs of inflammation in the brain were also evident and may have contributed to the behavioral changes.
“This paper suggests that high-fat diets impair brain health, in part, by disrupting the symbiotic relationship between humans and the microorganisms that occupy our gastrointestinal tracks,” commented Dr. John Krystal, Editor of Biological Psychiatry.
Study: Obese-type Gut Microbiota Induce Neurobehavioral Changes In The Absence Of Obesity, Biological Psychiatry, 1 April 2015
The present findings represent the first definitive evidence that high-fat diet-induced changes to the gut microbiome are sufficient to disrupt brain physiology and function in the absence of obesity. Specifically, data show that transplantation of microbiota shaped by high-fat diet, but not control low-fat diet, caused significant and selective disruptions in exploratory, cognitive, and stereotypical behavior in conventionally housed, nonobese, diet-naïve mice.
The human gastrointestinal tract harbors as many as 100 trillion bacteria from up to 1000 distinct species, and this dynamic population of microbes participates in numerous physiologic functions including nutrition/digestion, growth, inflammation, immunity, and protection against pathogens.
As usual, they ended by saying there may be a future for microbiome therapy, either the oral or injectable route:
“Overall, these data strongly suggest that therapeutic manipulation of the microbiome, which should be highly responsive compared with existing clinical targets, could dramatically mitigate the prevalence and/or severity of neuropsychiatric disorders.”
But … Probiotic pills contain just several billion organisms. That’s a drop in the bucket compared to the 100 trillion that line our GI tract. Getting the probiotics we take by mouth down there, and still viable, is a challenge. But a bigger challenge may be having them establish residence and multiply. Continuing to eat a high-fat diet would discourage that growth, and encourage growth of exactly the type of bacteria you’re trying to supplant. What you eat matters.*
* The non-obese control mice, who had a healthy gut microbiome, ate low-fat (13.5% fat, 58% carbohydrate). The obese mice, who developed an unhealthy gut microbiome, ate low-carb, high-fat (20% carbohydrate, 60% fat).