The brain protein amyloid-beta, which is an indicator of Alzheimer's, was reduced in mice given the ketogenic diet.

Interaction of Dietary Components

Samuel Henderson of Colorado-based pharmaceutical company Accera and colleagues in Belgium made the findings, which contradict previous studies suggesting a negative effect of fat on Alzheimer's disease.

"This work supports the premise that key aspects of Alzheimer's disease can be altered by changes in metabolism. It also highlights the interaction of dietary components and how such components influence the metabolic state," say the authors.

Insulin and the related hormone IGF-1 (insulin-related growth factor-1) are the key players, they believe.

"Insulin is often considered a storage hormone since it promotes deposition of fat, but insulin may also work to encourage amyloid-beta production," the researchers note.

Cognitive Improvements

"You might say that fat is the bomb, and insulin (from carbohydrate) is the fuse," explains Richard Feinman, editor of the journal.

"Most studies of the deleterious effects of fat have been done in the presence of high carbohydrate. If carbs are high, dietary fat is not oxidized and is instead stored as body fat," he points out.

When carbohydrates are very low and fat is high, compounds called ketone bodies are generated in a process called ketosis, and these compounds may play a role in the observed reduction in amyloid-beta.

Working with a University of Washington group led by Dr. Suzanne Craft, Henderson previously has demonstrated cognitive improvement in patients with mild AD who were given a diet that raises ketone bodies.

Understanding Metabolism

"Although it is too early to tell how the results will fit into the treatment of AD, the implication for diet in general is also important," Feinman says in an accompanying editorial.

The popular weight-loss diets based on carbohydrate restriction are based on the importance of insulin as a control element. Such regimens allow dieters to regulate fat and calorie intake by appetite alone as long as carbohydrate intake remains minimal.

"Henderson's effort is one of several recent studies that point the way to understanding metabolism beyond the issues surrounding simple fat reduction," Feinman notes.