For the brain to function properly, it needs a minimum of 130 carbohydrates a day and the brain prefers glucose, or carbohydrates, for fuel. Plus I don't think the fatty acids can cross the blood brain barrier efficiently? Maj, what has your experience being semi paleo with ketosis? Has it negatively effected your cognitive functioning?
Its quite the opposite - brain prefers ketones, contrary to everything you heard about it. I can send you references later if you want, but here is
one or
this case study, quick from the head. See
thisbook for latest info. The brain needs adaptation tho - it can live on very low amounts of glucose per day and drive most of its functions with ketone bodies (between 65-80% after adaptation). This adaptation is achieved over several weeks, 2 weeks being the norm (hence the reason why Atkins had initialization protocol). Muscles need more time, like 1-2 months, until physiological insulin resistance is achieved to spare glucose for the brain, then results in sport activities are better then on sugar. To boost ketogenic status of your body and prevent low carb blues you can ingest big amounts of pure, organic, cold pressed coconut oil. (15-30g per day in divided doses), the only substantial natural source of medium chain trygliceride (MCT) which absorb as quickly as sugar and give you fast energy (now they are used in sport drinks to recover energy).
Sugar actually gives quick boost to brain, probably by providing enhanced tryptophan absorption via blood brain barrier and hence serotonin biosynthesis, but its short fix, with postprandial hypoglicemia beeing the well known risk. Since Alzhamier is now more and more being classified as diabetes type 3, it makes sence to adopt low carb, ketogenic diet (high fat, moderate protein, low carb diet).
Other fatty acids can or can't cross BBB but this domain is not yet understood well - for instance, BBB can synthetisize DHA or maybe even EPA (fish oils) from its precursor, essential fatty acid ALA (flax oil). In any way, the only two fuels are glucose and ketone bodies and on fasting treatment for obesity you basically live on ketones for weeks or months, without any side effects. Keep in mind that diabetic ketoacidosis is not the same as this, natural ketosis.
So, all in all, with ketogenic diet your brain should flourish, work much better, you will delay aging phenomena like dementia, you will be more protected from infections, and the best of all, your vitamin C will work many times better since there is no glucose surges to block GLUT receptors.
One important additional benefit of low carb diet is that it eliminates dental disease almost 100%, which is very important because moth can be big source of focal infections which can then influence various parts of the body, most notably cardiovascular system and heart.
You may be genetically uncompatible with ketogenic diet - if your liver is in bad status and hence can't supply enough of glucose for cells that don't have mitochondria (some WBC, RBC and some for brain), you will get hypoglicemia (easily checkable with finger sugar meter or via sympthoms) or if you pancreas alpha cells that secrete glucagon are damaged and your adrenal is damaged at the same time (hence no cortisol to boost gluconeogenesis in context of missing glucagon, the primary mechanism). You can have damaged beta oxidation pathways of mitochondria (low amount of CPTI enzyme, or carnitine [probably not cuz of C]) in which case longer fatty acids (more then 12 carbons) will not be able to enter mitochondria, but MCT will still work. You may have selenium deficiency which can be detrimental.
So, don't worry, check it out, make sure you eat brazil nuts, buy some good coconut oil and keep carbs low (20-50g daily) - basically all animal products and all vegtables and nuts - no fruit, no grains, no rice, potatoes, good w-6/w-3 ratio ( 1-4 : 1 ) but low amounts of PUFA in general. You can eat very black chocolate 85% ++ cocoa all you want.
In my case, I completely eleminated postrapndial sleepeness that troubled me for years before it, flatulence, hemorrhoids, meteorism, I sleep better. On negative side, skin didn't change and I have some new eczmea patches, nothing serious so far. I didn't notice any cognitive effects apart from missing brain fog which I regularly had after wake up for few hours almost every day for decades.
Keep liver healthy by using milk thistle, NAC, vitamin C and other good products. You probably need less vitamins with it then otherwise if organs like liver and heart are part of the diet.