Are Carbs Helping or Destroying Your Brain?

Your brain is a complicated organ.  Extremely complicated.

In fact, the human brain is complicated enough that the human brain can’t even understand the human brain.

Modern science has discovered many interesting factoids about how our brains function, including things like the location of our memory center, the location of our speech center, where long term memories are formed, and how sleep restores neurological function.

Yet despite a very deep understanding of this mysterious organ, scientists routinely debate the answer to an incredibly basic question:

Are carbohydrates good or bad for your brain?

It’s a simple question, really.  But the answer is complicated.  Very complicated.

Attempting to understand how to fuel your brain optimally is a challenging task indeed.  Read 10 articles on the internet and you’re presented with 10 different answers. Read 10 more articles and you’re bound to get extremely confused.

In the quest for understanding what foods fuel your brain optimally, there seem to be two main reoccurring themes, shown below.

In order to get to the bottom of this debate, let’s dig into basic brain physiology.


Theme #1: Your brain loves carbohydrates

Your Brain Is A Glucose Hog

Make no mistake, your brain is the most selfish organ in your body.  Think of your brain as a metabolic pig – constantly taking energy from the bloodstream and storing none of it for itself.  It’s no wonder that your brain is one of the hungriest organs in your body – more than 80 billion neurons are sending and receiving electrical signals 24 hours a day, creating complex thoughts and emotions.  Even when you are  asleep, neurons in your brain are busy sending a flurry of electrical signals from one region to the next, consolidating memories and information from the previous day.  To put things in perspective:

Your brain occupies only 2% of your body weight but consumes about 20% of your body’s oxygen and up to 50% of your body’s glucose.

When it comes to food, your brain acts like a picky child, burning glucose almost exclusively.  Your brain is specifically designed to operate on glucose for 99% of your waking life, and when glucose is in short supply, the results can be disastrous.  If you’ve ever had the opportunity to experience hypoglycemia (low blood sugar) or if you are diabetic, the symptoms are unmistakable: confusion, lightheadedness, a loss of balance, slurred speech, and impaired vision.

Hypoglycemia Is Brain Starvation

Given what we know about the brain’s ability to use only glucose as fuel, when the concentration of glucose in the bloodstream falls, the brain is one of the first organs to recognize a problem.  In this situation, your brain is literally being starved for fuel, which results in feelings of confusion, lightheadedness, and slurred speech.  This situation can be very dangerous and even fatal, which is why it is very important to ensure that you recognize the symptoms immediately, then consume carbohydrate-rich food to restore brain function once again.

The Diabetic Brain Hates Simple Sugars

Since glucose is the most important brain fuel, it stands to reason that a diet containing easily available carbohydrate can make a significant positive impact on cognitive ability.  Studies have shown that eating carbohydrate-rich whole foods can improve memory within an hour after ingestion, and that glucose from simple sugars actually impair brain function1.

In a 2007 study entitled Dietary Influences on Cognitive Function with Aging, the authors describe how diet can affect brain function, and reason that “…[diets] high in fruits, vegetables, cereals, and fish are associated with better cognitive function and lower risk of dementia1.”

If you’re the lucky owner of a diabetic brain, then it is important to understand that simple sugars have detrimental effects on cognition.

The authors state, “Special care in food selection at meals should be exercised by those with type 2 diabetes since ingestion of rapidly absorbed, high–glycemic index carbohydrate foods further impairs medial temporal lobe function, with food-induced increases in oxidative stress and cytokine release likely explaining the association between food ingestion and reduction in cognitive function in those with type 2 diabetes1.”

In a similar study conducted in 2005, Greenwood and colleagues showed that a high fat diet sets the stage for insulin resistance, which itself causes significant cognitive defects in type 2 diabetic subjects2.

This is my take on that famous “This is your brain on drugs” advertising campaign from the early 1990’s:


Restricting Carbs Impair Brain Function in the Short Term

In the short term, restricting carbohydrate intake can dampen overall cognitive function3.  In a study conducted in 2008, women placed on a low-carbohydrate diet for 28 days suffered from impaired reaction time and reduced spatial memory than did women placed on a high-carbohydrate diet.  The researchers concluded that, “The brain needs glucose for energy and diets low in carbohydrates can be detrimental to learning, memory and thinking4.”


Theme #2: Your brain doesn’t need carbohydrates 

For centuries, remote civilizations like the Eskimos and Masai have subsisted on a near-carnivorous diet containing little to no carbohydrates from fruits and vegetables.  This stands to reason that our brains don’t require carbohydrates at all, and are capable of operating perfectly in a glucose-poor environment.  How is this possible?

On low- or no-carbohydrate diets, your liver and brain participate in a coordinated metabolic symphony.  Your liver takes on the job of making the fuel for your brain, and your brain responds by adapting to a new fuel source.

Fuel #1: The liver converts protein into glucose and sends it to the brain for immediate use.

Fuel #2: The liver converts fat into ketone bodies and sends them to the brain as an alternative fuel.

Ketone Bodies are Your Brain’s Alternate Fuel Source

A high intake of protein and fat provide the building blocks for an alternate brain fuel – ketone bodies.  Think of ketone bodies as a secondary fuel source for your brain when carbohydrates are running low.

In the same way that your laptop computer has a backup battery when a wall outlet is unavailable, ketone bodies are the backup power source for your brain when carbohydrates are out of reach.

Your Brain Takes Up To 2 Weeks to Fully Adapt to Ketone Bodies

Switching from glucose to ketone bodies takes time, which is part of the reason why a rapid switch from a high to a low-carbohydrate diet can feel painful.  But after a short period of transition, the brain fully adapts to ketone bodies for fuel.  Some researchers believe that the brain is actually more efficient when running on ketone bodies than it is on glucose, resulting in “a decreased seizure risk and a better environment for neuronal recovery and repair.”

 Ketone Bodies Can Persist for Long Periods of Time

Once your brain is fully keto-adapted, it is capable of functioning on ketone bodies for long periods of time – weeks, months and even years.  The short term effects of keto-adaptation seem to be benign, and I have yet to find research that studies the long-term effects of keto-adaptation.  Since the study of low carbohydrate diets is a relatively new science, long term studies are sure to clear up the confusion that many scientists have in understanding whether keto-adaptation is beneficial or detrimental in the long term.

 Take Home Messages

Depending on what you want to believe, there is plenty of evidence to support that both low carbohydrate diets and high carbohydrate diets provide optimal brain function.

So what’s the truth?

If you are like me, and are a proponent of REAL carbohydrate nutrition, then tattoo this to the inside of your arm:

Consuming carbohydrates from whole foods such as fruits, vegetables and legumes provide a high-quality fuel for brain function that is superior to glucose and fructose-sweetened processed foods.  Eat plenty of carbohydrates for optimal brain function.

If you want to justify eating a diet high in protein and fat, then memorize this statement instead:



1.  Parrott, M. D. & Greenwood, C. E. Dietary Influences on Cognitive Function with Aging. Ann. N. Y. Acad. Sci. 1114, 389–397 (2007).

2.  Greenwood, C. E. & Winocur, G. High-fat diets, insulin resistance and declining cognitive function. Neurobiol. Aging 26 Suppl 1, 42–45 (2005).

3.  Halyburton, A. K. et al. Low- and high-carbohydrate weight-loss diets have similar effects on mood but not cognitive performance. Am. J. Clin. Nutr. 86, 580–587 (2007).

4.  D’Anci, K. E., Watts, K. L., Kanarek, R. B. & Taylor, H. A. Low-carbohydrate weight-loss diets. Effects on cognition and mood. Appetite 52, 96–103 (2009).



Image Credits:


About The Author

Cyrus Khambatta

Diagnosed with type 1 diabetes at the age of 22, I have spent over a decade learning the fundamentals of nutrition at the doctorate level. My goal is to share my knowledge of practical nutrition and fitness with people with prediabetes, type 1 and type 2 diabetes. Diabetes is an OPPORTUNITY to attain excellent health. Reversing the effects of insulin resistance can be a fun and enjoyable process if the right system is in place. That's why I've spent over 10 years developing a rock solid system that can minimize blood glucose variability and insulin resistance.

Leave a comment or question below