What to eat for a healthy brain
Although likely not a comprehensive list of every single food item to eat and not eat for brain health (and I highly doubt there is currently enough knowledge to document such a large database in the first place), there are definitely clear trends regarding which food items consumed promote or degrade brain health.
Overall, a "Mediterranean diet" is perhaps one of the best diets undertaken for a healthy brain. This is not to limit it to only Mediterranean-specific foods. Essentially, the Mediterranean diet refers to consuming proportionally higher fat and protein, and lower carbohydrates.
Glucose and fructose have shown to decrease activation in brain regions, such as the anterior cingulate cortex (involved in attention, learning, and memory), and induce neural death via apoptosis. Glucose has also shown to induce inflammation and promote neurodegeneration. A large body of further evidence comes from major links between diabetes mellitus and cognitive diseases. These are only a fraction of the numerous sources indicating the negative impact of glucose on brain health, many of which are cited by Dr. Perlmutter. In fact, he goes as far as to proclaim that a pure ketogenic diet for life would be beneficial for one’s brain. I personally would take it with a pinch of salt, as we have not yet documented the effects of all various foods within a ketogenic diet itself to brain function - but definitely endorse the clear data indicating that glucose disrupts brain health in the long term.
Although the reason behind its occurrence is not entirely known, there are several understood mechanisms as to why this occurs. First, is the reduction in ability for LDLs (Low Density Lipoproteins) to carry cholesterol to the brain. As the brain is made of around 20–25% of cholesterol, this is not necessarily good. Second, glucose combines with proteins and fats to form advanced glycation end products (AGEs) that essentially promote oxidative stress and induce aging. Third, gluten sensitivity can create anti-gluten antibodies, which then begin to induce inflammation that carries on to the brain. Glucose also activates cellular stress pathways such as TNF-alpha (Tumor Necrosis Factor), which are likely a result of the aforementioned processes. Furthermore, sugars lower BDNF (which promotes neurogenesis - i.e, the formation of new neurons). They also increase the likelihood for insulin resistance, which has been linked to the formation of amyloid plaques so characteristic of Alzheimer’s and similar pathologies.
Additionally, consume antioxidants - such as circumin, DHA, Resveratrol and polyphenols found in food items such as turmeric powder, seafood / DHA supplements, red wine, green tea and cocoa. This is because antioxidants primarily work by eliminating free radicals generated by cellular processes that would otherwise interfere with protein folding and potentially damage neurons.
I have briefly touched on this earlier, but it’s also important to consume cholesterol - much of the heart-related scares have greatly lowered general perceptions about cholesterol - but these are incredibly useful for one’s neural health. Cholesterol makes up approximately 25% of the brain, and numerous studies have linked lower cholesterol with greater cognitive decline. It’s roles essentially encompass optimal hormone production, ensuring membrane fluidity, synapse formation, dendritic growth, axon elongation, and neuroplasticity. Although cholesterol is produced within the brain itself, consuming cholesterol raises LDL/HDL levels in the blood, which aids transport of cholesterol to the brain.
Also, simply put, do not become overweight and ensure adequate exercise. Studies have shown physical reductions in brain size with increased BMI. Attempt to limit your calories (not too much however), as it has shown to elevate BDNF levels, thus reducing cognitive decline.