The paper looked at a Mediterranean diet, the DASH diet (Dietary Approaches to Stop Hypertension), the MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay), and ketogenic diets, and also singled out cocoa, lion’s mane mushroom, and select spices, as being potentially beneficial for brain health. There were several references to various aspects of these dietary patterns and individual elements having anti-inflammatory or antioxidant effects, but the section on ketogenic diets was the only one that mentioned one of the fundamental aspects of Alzheimer’s disease (AD), which is a glucose-specific fuel deficit in the brain.
Alzheimer’s is increasingly considered to be a form of brain insulin resistance, and as this paper stated, “Ketones may provide an alternative energy source for the brain with prominent insulin resistance.” While the AD-afflicted brain is impaired in taking up and metabolizing glucose, no such impairment in ketones has been observed. To the contrary, brain ketone uptake is not altered in AD or its precursor, mild cognitive impairment. Regarding keto, the paper notes, “The diet involves the restriction of carbohydrates to the point where the body produces ketones, which can be an alternative, beneficial fuel for the brain.”
Points of overlap between the diets profiled include very little sugar and processed foods, a variety of vegetables, and inclusion of specific fats (particularly long-chain omega-3s and monounsaturated fats). Major points of difference include restrictions or limitations on saturated fats, full-fat dairy products, and animal proteins other than fish and poultry. Keto diets include these, while the others don’t, and the others include fruit, beans, and whole grains, which are too carbohydrate-dense to fit into a keto diet except for lower-sugar fruits such as berries.
It must be noted that, at this point, any associations between certain dietary patterns and disease incidence are only that: associations. It is not possible to establish cause and effect using epidemiological or observational research. At best, this type of evidence can be hypothesis-generating but it cannot establish causal links. (Except in the case of smoking and lung cancer, for which the association was so strong as to be undeniable. Associations that strong are rarely seen in even the most rigorous nutritional epidemiology.)