Ketogenic Diet in Neurodegenerative Diseases

Ketosis. It has become one of the most popular words of the 21st century. Often connected to weight loss, “ketosis” is also strongly associated with epilepsy: the ketogenic diet was first introduced by clinicians as a treatment for epilepsy in the 1920s. Over the last decade, researchers have been studying the effect of ketosis on other neurological and mitochondrial disorders, with promising results.

In ketosis, the mitochondria burn fat instead of glucose for energy metabolism. Ketosis can be achieved through periods of fasting or by reducing the intake of carbohydrates in the diet, leading the body to break down fatty acids to produce higher-than-normal levels of so-called ketone bodies—acetoacetate, beta-hydroxybutyric acid, and acetone—through a process called ketogenesis, which occurs principally in the mitochondrial matrix in the liver.^>1 The “state of ketosis” has been shown to exert a protective action against neurological diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and more.^1,2,3 In AD and PD, single human studies have shown a reduction of disease symptoms in participants following a ketogenic diet.⁴

A therapeutic ketogenic diet has been studied by Functional Medicine clinician Terry Wahls, MD, with the specific aim of reversing the symptoms of multiple sclerosis (MS). Such diets have been shown to stimulate mitochondrial biogenesis, improve mitochondrial function, and reduce oxidative stress.^2,3 Dr. Wahls has used ketogenic diets in her clinical practice for a wide variety of health issues that result from mitochondrial disease. In the following IFM video, Dr. Wahls talks about the importance of diet for patients with neurological disease symptoms like chronic fatigue.

The first randomized controlled trial of the ketogenic diet with medium-chain triglycerides in humans with AD or mild cognitive impairment showed that higher ketone values were associated with greater improvement in paragraph recall.⁵ In a 2007 study, ketone bodies were reported to act as neuroprotective agents by raising ATP levels and reducing the production of reactive oxygen species in neurological tissues, together with mitochondrial biogenesis, which may help to enhance the regulation of synaptic function.¹ Caloric restriction, in and of itself, has also been suggested to exert neuroprotective effects, including improved mitochondrial function, decreased oxidative stress and apoptosis, and inhibition of pro-inflammatory mediators, such as the cytokines tumor necrosis factor-alpha and inflammatory interleukins.¹

In a 2009 randomized double-blind study, patients with mild and moderate AD who were administered medium-chain triglycerides showed increased serum concentrations of ketone bodies and improved cognitive functioning.⁶ In a 2018 Ketogenic Diet Retention and Feasibility Trial, 15 patients with AD were put on a medium-chain triglyceride–supplemented ketogenic diet (approximately 70% of energy as fat, including the MCT; 20% of energy as protein; and less than 10% of energy as carbohydrates); researchers observed that in a state of ketosis, the mean of the Alzheimer’s Disease Assessment Scale cognitive subscale score improved significantly during the diet and reverted to baseline after the washout.⁷