It turns out, you can “hack” your diet to reduce your risk of getting Alzheimer’s disease, says a recent study by Wake Forest School of Medicine in North Carolina. In the report, a team of researchers showed how diet could influence gut bacteria, which, in turn, can stop the progression of mild cognitive impairment (MCI). In particular, they identified several distinct microbiome signatures in the gut microbiome of patients with MCI.
The team also revealed how a modified Mediterranean-ketogenic diet affects the gut microbiome, in particular, when it comes to reducing biomarkers for Alzheimer’s disease.
“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,” explained Dr. Hariom Yadav, a professor molecular medicine at Wake Forest and a co-author of the study.
The team published their findings in EBioMedicine.
Exploring the brain-gut connection
Alzheimer’s disease is a neurodegenerative disease that affects memory, thinking and behavior. The disease affects more than 5 million Americans, according to the Alzheimer’s Association. Despite its prevalence, the exact cause of the disease remains unclear. There are also no accepted mainstream cures or therapies for treating it outside of adopting healthier habits, such as exercising and cutting back on foods that can affect brain health. (Related: The risk factors of Alzheimer’s disease.)
Scientists have recently begun to explore the feasibility of nutritional approaches in reducing the risk of neurological conditions like Alzheimer’s. For the most part, this emerging area of research is borne out of the idea that gut health might be linked to brain health.
A team of researchers from the University of Wisconsin’s School of Medicine and Public Health and the University of Gothenburg reported back in 2017 that the gut microbiome might be linked to the progression of Alzheimer’s.
This report came about after the team isolated fecal samples from Alzheimer’s patients to compare their gut microbiome to that of control participants. They found that the gut microbiome of those in the Alzheimer’s group had less microbial richness.
The Alzheimer’s group also had more pro-inflammatory bacteria in their gut. This finding is significant because chronic inflammation raises the risk of Alzheimer’s and exacerbates its symptoms in patients.
Based on their findings, the researchers thus concluded that determining the role of gut bacteria in the progression of Alzheimer’s can lead to treatments in the future that modulate gut microbiome for better brain health.
MMKD alters gut bacteria and reduces Alzheimer’s risk
In support of these findings, researchers of the EBioMedicine study affirmed that the risk of Alzheimer’s is tied to gut health after finding similarities among the gut microbiome signatures of 11 MCI patients but not among those of the six cognitively normal (CN) participants.
It should be noted that MCI is not a form of dementia, but it does cause neurological problems that cannot be considered a normal part of aging. MCI also places patients at a greater risk of dementia in later life.
Upon analysis of fecal samples, the team found that MCI patients had a higher amount of bad gut microbes called Firmicutes. These bacteria are linked to metabolic conditions like diabetes and obesity.
In addition, the MCI patients had inadequate amounts of Bacteroidetes, a genus of beneficial gut bacteria. Their guts also lacked bacterial diversity. All three findings are signs of an imbalanced gut or poor gut health.
Furthermore, the gut microbiome similarities across the MCI patients also corresponded to increased biomarkers of Alzheimer’s. This suggests that poor gut health is linked to a greater risk of the disease.
The team then conducted a randomized, double-blind trial on both groups to see if changes in diet can alter the gut microbiome and, in doing so, minimize the risk of Alzheimer’s.
For the dietary intervention, the team randomly assigned each participant either an MMKD or a low-fat diet for six weeks. After a six-week washout period, each participant should then follow the other diet for another six weeks.
The researchers took fecal samples from all participants before and after each dieting period to monitor changes in their gut microbiome. They also measured ketones from blood samples and biomarkers of Alzheimer’s from the participants’ cerebrospinal fluid.
Past studies found that greater adherence to a Mediterranean diet is linked to reduced incidences of chronic diseases, including Alzheimer’s. On the other hand, the ketogenic diet has been found to alter the gut microbiome in mice.
For these reasons, the researchers combined both diets to form a modified Mediterranean-ketogenic diet comprised of fruits, vegetables, carbohydrates, extra-virgin olive oil, lean meat and fish. Many of these foods are thought to reduce the risk of Alzheimer’s disease and dementia.
The other diet also featured fruits and vegetables, but it restricted fat intake to less than 40 grams per day. Additionally, 50–60 percent of the total caloric intake under this diet is expected to come solely from fiber-containing carbohydrates.
After both dieting periods, the team found that the MMKD did produce changes in the gut microbiome that corresponded to reduced levels of biomarkers of Alzheimer’s in both groups.
Therefore, MMKD did slash not only the risk of Alzheimer’s in MCI patients but also reduced biomarkers of Alzheimer’s in those that had normal levels of cognition.
The study findings also underscore the need for future clinical studies that focus on the role of the gut microbiome in reducing the risk of and stalling the progression of Alzheimer’s disease.
The team further noted that these findings could be used in the creation of nutritional and therapeutic approaches against the disease in the future that take the role of gut health into account.