A small pilot study suggests that Alzheimer’s disease is linked to specific changes in gut bacteria, and that a type of ketogenic-Mediterranean diet can affect the gut microbiome in ways that could potentially decrease the risk of Alzheimer’s disease.
The ketogenic diet is very low in carbohydrates and high in fats, and the traditional Mediterranean diet focuses on vegetables, fruits, fish, nuts and healthy fats. The diet in the study was a modified version of these.
For the study, researchers from Wake Forest School of Medicine in North Carolina identified several distinct gut microbiome signatures — the chemicals produced by gut bacteria — in study participants with mild cognitive impairment (MCI) but not in their counterparts with normal cognition.
They also found that these bacterial signatures correlated with higher levels of markers of Alzheimer’s disease in the cerebrospinal fluid of the participants with MCI.
Through cross-group dietary intervention, the study also showed that a modified Mediterranean-ketogenic diet produced changes in the gut microbiome and its metabolites that correlated with reduced levels of Alzheimer’s markers in the members of both study groups.
“The relationship of the gut microbiome and diet to neurodegenerative diseases has recently received considerable attention, and this study suggests that Alzheimer’s disease is associated with specific changes in gut bacteria and that a type of ketogenic Mediterranean diet can affect the microbiome in ways that could impact the development of dementia,” said Hariom Yadav, Ph.D., assistant professor of molecular medicine at Wake Forest School of Medicine.
Yadav co-authored the study with Suzanne Craft, Ph.D., professor of gerontology and geriatric medicine at the medical school and director of Wake Forest Baptist Health’s Alzheimer’s Disease Research Center.
The randomized, double-blind, single-site study involved 17 older adults, 11 with diagnosed MCI and six with normal cognition. These participants were randomly assigned to follow either the low-carbohydrate modified Mediterranean-ketogenic diet or a low-fat, higher carbohydrate diet for six weeks then, after a six-week “washout” period, to switch to the other diet.
Before and after each dieting period, the researchers evaluated the participants’ gut microbiome, fecal short-chain fatty acids and any markers of Alzheimer’s (including amyloid and tau proteins) in their cerebrospinal fluid.
The study’s limitations include the subject group’s size, which also accounts for the lack of diversity in terms of gender, ethnicity and age.
“Our findings provide important information that future interventional and clinical studies can be based on,” Yadav said. “Determining the specific role these gut microbiome signatures have in the progression of Alzheimer’s disease could lead to novel nutritional and therapeutic approaches that would be effective against the disease.”
The study appears in the journal EBioMedicine.