Is a keto diet or supplemental ketones useful for treating cognitive decline?

One major factor in cognitive decline is that the brain can fail to obtain enough energy to function properly, be it from vascular problems or insulin resistance.^[1][2][3] A keto diet is believed to provide a neuroprotective benefit by reducing oxidative stress and increasing mitochondrial respiration.^[4]

A keto diet is also believed to provide benefits by reducing the oxidation of glucose and leading to calorie restriction,^[4] neither of which would necessarily be achieved through the use of exogenous ketone supplements. The few studies available on people with Alzheimer’s disease suggest that a ketogenic diet may provide potential benefits, but ultimately needs to overcome a brain energy deficit.^[5] By this logic, exogenous ketones could be beneficial by allowing both glucose and ketones to act as fuel sources for the brain.

Research investigating the role of exogenous ketones in neurodegenerative diseases and cognitive decline is lacking. What studies are available test cognitive function in healthy adults after a bout of endurance exercise. These studies suggest that supplementing with exogenous ketones either benefits cognitive function when combined with carbohydrates, as compared with carbohydrates alone,^[6] or provide no benefit when taken alone, as compared with a noncaloric placebo.^[7]