High fat diet may keep brain young, study suggests

A ketogenic diet rich in fish, berries and nuts could help improve brain health in people at higher risk of developing Alzheimer’s disease, new research suggests.

The high-fat, low-carbohydrate diet — also known as a ketogenic diet — showed particular promise for women with the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease.

Researchers found that switching to this diet altered gut bacteria and improved brain energy levels in female mice carrying the APOE4 gene, suggesting a potential way to intervene before symptoms begin.

Scientists from the University of Missouri-Columbia discovered that the diet helped the brain use alternative fuel sources when glucose processing becomes impaired, a common problem in APOE4 carriers that can lead to cognitive decline.

“When we eat carbs, our brains convert the glucose into fuel for our brains, but those with the APOE4 gene – particularly females – struggle to convert the glucose into brain energy, and this can lead to cognitive decline down the road,” study co-author Kira Ivanich explained.

The ketogenic diet works by prompting the body to produce chemicals called ketones as an alternative energy source.

These ketones may help preserve brain cell health and reduce the likelihood of developing Alzheimer’s disease.

A previous study found that female mice carrying the APOE4 gene developed healthier gut bacteria and showed higher brain energy levels when fed a ketogenic diet compared with those eating more carbohydrates.

The latest research built on this work, revealing specific bacterial changes that could explain the brain benefits. The diet increased beneficial bacteria species while reducing potentially harmful ones.

“Ketogenic diet increased beneficial species such as Lactobacillus johnsonii and Lactobacillus reuteri while reducing pathogenic Bacteroides intestinalis,” the study noted.

These gut bacteria shifts were found to support key brain functions, enhancing mitochondrial activity — the cell’s energy producer — as well as fat metabolism and the balance of important brain chemicals called neurotransmitters.

These findings highlight the ketogenic diet’s potential to reprogram the gut–brain axis,” scientists said, referring to the communication network between the gut and the brain that influences mood, cognition and overall brain health.

The researchers said dietary interventions should be tailored to those who would benefit most, rather than applying a one-size-fits-all approach.

Instead of expecting one solution to work for everyone, it might be better to consider a variety of factors, including someone’s genotype, gut microbiome, gender, and age,” said Ai-Ling Lin, another author of the study.

The timing of intervention also appears crucial. Alzheimer’s symptoms typically emerge after age 65 and tend to be irreversible once they begin, making prevention especially important for high-risk individuals.

“Since the symptoms of Alzheimer’s – which tend to be irreversible once they start – usually appear after age 65, the time to be thinking about preserving brain health is well before then, so hopefully our research can offer hope to many people through early interventions,” Lin added.