I won’t be able to fully answer the question whether fats are brain healthy or not.  But I will point you to references on both sides for you to study for hours on end to see if you can draw your own conclusion.

Note that everything mentioned in this article has a rebuttal against what was mention as well as a confirmation of what was mention.  I can only provide my own personal opinion, which may or may not be correct.

This is because of all the fields of study, the field of nutrition is one of the most contentious and debatable (even more controversial than quantum mechanics and the study of the stock market).  And within the field of nutrition, the subject of whether eating fat is good for you or not is among the more controversial.

Clearly, the answer is that healthy fat is brain healthy.  And unhealthy fats are not brain healthy.  There is a spectrum of which somewhere in the middle is the correct balance that is most beneficial to the brain.  A brain with no fat is not healthy.  And a brain with all the wrong fats is also not healthy.

The question is what is considered “healthy fat” for the brain.  There are three main categories of fat polyunsaturated, monounsaturated, and saturated fats.   And within those category are finer categories of each, but we won’t go that deep.

Polyunsaturated (such as vegetable oils) are most easily damaged or oxidized by heat.  Saturated fats (such as coconut oil and animal fats) are least easily damaged.  And monounsaturated fats (such as olive and avocados and its oils) are in between.

Types of Fats

Oxidized fats are unhealthy to the brain.  Therefore, heated vegetable oils and its use in cooking is not healthy.   Since most restaurants and especially fast food places uses some form of vegetable based oils, it is healthier to cook at home. Better to cook with more heat resistance olive oils (for light heat as in sauteing vegetables) or coconut oil (for cooking meats).   See what is the best oil to cook with.  Chris Kresser recommends cooking with these five saturated-based fats.

Speaking of cooked meats.  Are the cooked saturated fats in meats healthy?  According to Dr.  Gabriel Cousens in his book “There is a Cure for Diabetes“, the answer is no.  He does not believe in cooked animal fats.  But he does believe in live uncooked fats from plant sources.

At 589 pages, his book is the most comprehensive and and technical explanation of diabetes and metabolism that I have read (and I have read quite a few books on the topic).  So I have extra credence to his opinions.

So my conclusion is that uncooked and unheated plant sources of fat, such as nuts, olives, avocados, coconut meat are healthy for the brain.

What about bacon? We can surmise that Cousens would say unhealthy because it is a highly cooked animal fat. Some say that bacon is actually 50% monounsaturated fat.

Dr. David Perlmutter is also “not a fan of bacon” (quoted from here).  He says in a video you need to be very selective about the types of fats.  And he writes “Avocados, grass-fed beef, organic olive oil, and wild-caught fish can help you build a better brain.” (reference).

While others in the Paleo community (including Chris Kresser) are okay with bacon and often consider saturated fats a healthy fat.  See Diane San Filippo, Chris Kresser, and Mark’s Daily Apple.

Seth Roberts says that his sleep (and by implication, his brain) improves when he eats pork fat — and he has charts to show it.  He says butter has the same effect.

Dr. Michael Greger tells of some stats (in this youtube) showing that vegetarian has no difference between the mortality rates of meat eaters and vegetarians.  Furthermore, vegetarian has twice the risk of dying from neuro degenerative brain disease.  The theory is that vegetarians might be lacking in omega-3 fats and vitamin B12 (found in fish and in animal meats respectively).  So there might be a case for eating meat.

My opinion… While I do believe in eating some fish and meats on a mostly plant-based diet, I’m with Cousens and Perlmutter and keep bacon at a minimum.  I’m not a fan of pork either because of this.

What about coconut oil which is mostly saturated fat?  I think it is brain healthy.   Coconut oil is high in medium chain triglycerides which is an immediately available source of energy.  Perlmutter says it is a good choice.  Dr. Mary Newport uses coconut oil to help her husband with Alzheimer’s.  Dave Asprey explains the benefits of MCT and coconut oil.

What about eggs?

Some would say the cholesterol in eggs is not an issue.  However, oxidized cholesterol might be.  Perhaps that is why Dr. Mercola eats his eggs raw and he eats “minimum of two eggs a day more typically four or sometimes as much as eight eggs a day.”  — referenced in this video of Dr. Mercola and Dr. Cousens.  Dr. Cousens tend to agree, but he doesn’t eat eggs because “he can’t stand eggs” (presumably of its taste or texture).   But there are people who are allergic to eggs.

Unhealthy Fats

Most people agree that trans fats such as deep fried foods is clearly bad. Cousens says in his book that natural saturated fats in meats when under high heat can change from “cis” to “trans” configuration of the molecule.

This study says that …

“In addition to impairments in exercise capacity, rats consuming a high-fat diet for 9 d, whether exercised or sedentary, showed a decline in cognitive function in a radial-arm maze test. … This represents a decline in working memory in those rats fed a high-fat diet, as they were less able to recall which arms of the maze they had previously visited during the test. … The mechanism underlying impairment in cognitive function in rats and humans ingesting a high-fat diet remains elusive”

By “high-fat”, they meant “containing 55% saturated fat” (but we don’t know if this is trans fat or not).

ABCScience says that …

“saturated dietary fat damages the lining of blood vessels in the brains of mice, allowing a protein called amyloid to enter the brain.”

and that …

“this lining, called the blood-brain-barrier, is damaged by high saturated fat diets. … saturated dietary fats increase the production of amyloid in the small intestine. … The saturated fat mice also had more amyloid deposits in their brain than those fed the monounsaturated or polyunsaturated diets.”