7. Brain-Dead on Ketones?

7. Brain-Dead on Ketones?

Considering glucose the “default” fuel, old dietary advice was to consume at least 150 grams of carbs daily, and preferably 250 grams, supposedly in order to provide sufficient fuel for the brain, which takes up about 20% of your total energy expenditure.

Repeated by almost every authority from the American Heart Association to Harvard University, this view is ridiculous, and it is increasingly being challenged by scientific studies and by anyone who can think straight.

Hello! Many people drastically cut carbohydrates or even all food intake for extended periods of time yet do not appear to be brain-dead.

It was unlikely that most predatory animals in the past billion years had “three square meals” a day, and especially not from carbs. Edible fruits, the kind with lots of fructose, evolved less than 100 million years ago. The carbohydrate-dense wheat, corn, rice, and potatoes we are familiar with today are all hybrids of recent origin, just a few thousand years old. Most plants are just leaves with poor nutrition value for a warm-blooded animal, which is why herbivorous animals have to eat all day.

More likely, our very distant aquatic or reptile ancestors would find prey or more occasionally edible plant food, gorge on it (storing the excess calories as body fat), then go hungry for several days or more until they found something else. In the meantime they were in some kind of fasting state, using not glucose but triglycerides from stored body fat (to emphasize, we are talking about distant epochs).

However there is a problem with triglycerides from body fat. Though they can cross the blood-brain barrier, they don’t break down fast enough to fuel the brain efficiently. Triglycerides can fuel muscles and organs, but are not good fuel for the brain, even a fish brain.

The evolutionary solution for vertebrates was ketosis, the process of turning stored fat into ketones. Ketones are a class of organic chemicals which are highly reactive and easily recombine or break down into other molecules. Relax, that’s all the chemistry you need to know. In our bodies, it is actually the mitochondria — the workhorses of our cells — that perform the chemical transformation of triglycerides into ketones.

Ketones can not only fuel the brain but do so better than glucose or triglycerides. This makes common sense in terms of evolution and natural selection: if you were a predatory animal, you needed to be even more alert when hungry than when just-fed. If you weren’t, you were at a disadvantage competing for prey, died young, and left no descendants. The ability to convert stored fat into ketones with which to fuel the brain confers a significant survival advantage: greater alertness and mental clarity when not fed recently. Most of the world’s religions recommend some form of fasting, and not because it makes you brain-dead.

Fast-forwarding to the somewhat recent past but still in pre-agricultural times, our usual fuel must have been ketones from stored fat earlier provided by meat, fat, low-carb plants, and the very occasional ripe mango. This only changed in recent millennia when we became farmers and had a steady daily supply of carbs, mostly from grains, whereupon we became carb-eaters, and glucose became the “normal” fuel used by our bodies and brains.

In numerous studies, people suffering from apparent cognitive issues were given ketone supplements, and showed mild but noticeable improvement in memory and clarity. The improvement may have been only “mild” because ketone supplements didn’t totally displace the glucose from carbs, which the patients were still eating. There is strong anecdotal evidence that when people fast or greatly restrict carb consumption, and are therefore burning mainly ketones, the improvements in mental function are considerable. There is increasing speculation that a Keto Diet (see more about diets later) may alleviate some of the symptoms of Parkinson’s Disease (https://nunm.edu/2025/07/ketogenic-diet-for-parkinsons-disease) and possibly other kinds of mental or psychological dysfunction.

Regrettably, many if not most practicing physicians around the world have not bothered to keep abreast of the continuing progress being made in understanding metabolism. Many doctors have only heard of “diabetic ketoacidosis” and confuse it with “ketosis”. Diabetic ketoacidosis is unique to Type 1 diabetics, whose bodies cannot make insulin at all. If deprived of their synthetic insulin injections, their blood glucose keeps rising, but without insulin the glucose still can’t be delivered to the cells as fuel. Sensing energy starvation in the cells, the body starts converting stored fat or muscle into ketones. This combination — high sugar and ketones — makes the blood acidic and toxic.

Deliberate ketosis through diet is not the same thing at all, in which ketones are released precisely because glucose has been used up. Anyone who bothers to think about our evolutionary history will readily figure out that ketones are more natural for fueling our bodies than carbs and glucose.