Scientists have found associations between fungi living in the gut and mild cognitive impairment, which can lead to Alzheimer’s disease. They suggest that a ketogenic diet could help prevent the disease by creating a more healthful balance of microorganisms in the gut.

Alzheimer’s Association report that 15–20% of people over 65 experience mild cognitive impairment (MCI), which involves a decline in memory and the ability to think clearly.

Doctors do not consider MCI to be a form of dementia because people who have it are able to function relatively well and live independently. However, MCI is associated with an increased risk of Alzheimer’s disease or another form of dementia later in life.

Developing preventive strategies that can be initiated early is therefore a priority. But despite decades of research, no therapies have been shown to reverse or prevent the brain changes seen in Alzheimer’s.

One potential strategy that scientists have begun to explore involves modifying the diet to influence the microbial communities in the gut.

There is an intimate relationship between the gut microbiome and the central nervous system, with recent research suggesting associations between particular bacterial communities and neurological disorders, including MCI, dementia, and Alzheimer’s.

In one recent study, scientists at the Wake Forest School of Medicine, in Winston-Salem, NC, found a distinctive gut bacterial “signature” in people with MCI.

They also discovered that a diet called the modified Mediterranean-style ketogenic diet altered bacterial communities in the guts of volunteers and reduced biomarkers of Alzheimer’s disease in the cerebrospinal fluid of those with MCI.

This diet contains a limited number of carbohydrates and increased amounts of fats. These are primarily mono- and polyunsaturated fats that come from olive oil and fish.

A ketogenic, or “keto”, diet contains very few carbohydrates, which the body uses as fuel. When short on carbs, the body starts to break down its fat reserves to produce molecules called ketones, as an alternative source of energy.

The same group of researchers now reports similar associations between the communities of fungi in the gut — collectively called the mycobiome — the person’s diet, and their risk of MCI.

The authors acknowledge that their study had some key limitations. First, while the researchers advised people to eat certain diets, they did not monitor the participants for this.

It was also a pilot study with a small sample size, making it impossible to account for other variables that might affect Alzheimer’s risk and the population of the gut’s microorganisms, such as lifestyle, gender, and ethnicity.

Moreover, the unique signature of gut fungi and bacteria found in individuals with MCI may be a result of the health issue, rather than one of its causes.

Finally, the changes in the mycobiome observed in the participants assigned the keto diet may have been transient, resulting from fungi in the food.

Medical reference: Medical News Today