What Nutrients Power The Brain?

Popular Wisdom Holds That The Brain Runs On Sugar. This Is A Frequently Used Excuse To Justify Eating A Lot Of Sugar And Starch. The Brainbrain-nutrition Needs A Lot More Than Sugar To Run Properly, and Excess Sugar Is Now Thought To Be The Most Likely Cause of Alzheimer’s.

Most doctors will tell you that the brain runs on glucose. Glucose is a type of sugar, and is sometimes called dextrose. Table sugar is half glucose and half fructose. All starches, in fact all carbs, end up as one of these, or a mix. The liver converts most of the fructose to glucose. So it’s all glucose, except the parts you can’t digest at all.

brain-eating-paperThe indigestible bits are called fiber, and getting enough of this is important. The richest sort is the colored vegetables, but the most advertised sort is whole grain. Today everything must be whole grain. This is odd when you think about it. All the dietary recommendations tell you to eat something that you can’t digest. If you want to get yet more fiber, you could consider eating the junk mail that arrives each day. It’s 100% fiber.

But we digress. What does the brain run on? It seems to prefer sugar, but it is not clear that this is in its best interests. The body will try to maintain sugar at around 75 mg/dl. This is about a teaspoon of sugar for your five quarts of blood. This sugar is marked “brain-only.” How does the body do this? Cells other than the brain are not allowed to consume any sugar unless there is an excess. This is the role of insulin. If insulin is low, the various cells, brain excepted, are ordered to leave sugar alone. The only non-brain cells that disobey this rule are those found in cancers. (Another reason to keep blood sugar low.)

After a meal that includes sugar and starch, sugar shoots up, and depending on the meal, possibly way up. Now that there is an excess, the body raises the insulin level—the hormonal dinner bell. In a healthy body, the muscle cells will gobble the sugar back down to 80 and then the dinner bell will stop ringing—insulin will drop.

However, if too much sugar and starch are eaten, the muscle cells fill up, the excess is converted to fat and stored in the fat cells. But even that has a limit. If still more sugar and starch are eaten, the glucose and insulin can stay elevated 24/7. The dinner bell keeps ringing, but there are no takers. Chronic excess sugar is the definition of adult onset diabetes, and also causes perhaps 80% of today’s other chronic medical problems (heart disease, cancer, etc.).

High chronic sugar levels are now thought to be the cause of Alzheimer’s. In fact, this disease is now being called type 3 diabetes.

So, too much sugar is bad all around, body and brain. But what about too little sugar?

Hunter-gatherers are at the other end of the spectrum: they consume almost no sugar and starch. (There are still over 200 tribes.) This seems to have no effect on their brains. When hunter-gatherers “mainstream” so to speak, they perform just as well, get PhD’s and the whole bit. Maybe they perform better. Amongst us “civilized” people, there has been a slight downward trend in brain size. (We hope this doesn’t continue, but given the idiotic way this planet is frequently managed, one wonders if the trend hasn’t accelerated.)

For hunter-gatherers, meaning 98% of our ancestry, glucose shortages were the norm. Since getting nourishment to the brain is crucial, there has to be a backup plan. The body has several.


The “gluco” is the sugar, and the “neo genesis” means making it from scratch. We have an amazing chemical factory, called the liver, that can cook up just about anything from brain-ketosisanything. The liver can make glucose from several different things. One of the more interesting is glycerol, which is the “glyce” in the ubiquitous fat molecule: triglyceride. It can also use lactate, certain types of protein, and some other items. Better living through chemistry.

But that’s not all.


Suppose the gluconeogenesis well runs dry. Then it’s on to Plan C. The liver will then make ketones up directly from fat. Acetone, the odiferous ingredient in nail polish, is the best known example, but three different ketones are made. The brain runs fine on these. But there is an unexpected result here.

It seems that when dementia patients are place on a ketogenic diet—no carbs at all—they get better! It’s not a cure by any means, but there is significant cognitive improvement. This was a bit of an unexpected result. (Many severe forms of seizures get better on a ketogenic diet as well.)

But circling back around to the sugar overload, if, indeed, dementia is caused by this overload (which appears to be practically dogma at this point), then we would expect benefit from cutting out all that sugar.

So what’s the conclusion? Your brain is never going to run out of fuel, regardless of your diet, and low carb may be the healthiest.

  4 comments for “What Nutrients Power The Brain?

  1. Paul Latter
    June 8, 2015 at 9:41 am

    Dear Doc;

    I am 64 years old and have both my parents alive at 90 years old. I find your blog very helpful. I want to try to avoid the health problems that my parents are encountering if I should live to 90. Your blog gives me hope!



  2. Paul Latter
    June 8, 2015 at 4:25 pm

    Does the production of ketones cause any stress to the liver? Does the human body work any better with some sugar? Are there any good sugars? If not should I avoid all fruit? I am all for a high protein diet, but my wife complains that I get bad breath from it. Is that a sign I need more veggies or something else in my diet? I like the idea of the Paleo Diet- but is there something better? Looking forward to reading your book.



  3. Linda
    September 25, 2015 at 3:13 am

    What the heck can we eat?….
    no sugar. no carbs. no grains
    Only meat, I have read that meat is supposed to be bad cause it lays in your stomach and rots

    • September 25, 2015 at 10:05 am

      Vegetables; an almost endless array of vegetables. Nuts and seeds. Lot’s of other good stuff! Dr. Mike
      P.S. Meat does not, does not, in any meaningful way ‘rot’ in your stomach.

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