Your body (including your brain tissue) has two simple options when it comes to creating energy: You can either use glucose (sugar) or fat.
Nearly every diet out there (including Atkins and Paleo) maintains glucose as the primary fuel source. Why? Because unless carbohydrates are restricted to between 20-50 grams per day, the body will fight to use sugar for energy. Sugar is a quick and easy (if problematic) source of energy--plus it triggers a dopamine and serotonin rush.
It’s only when glycogen reserves (stored sugar) are depleted that the body switches over to nutritional ketosis (fat-burning mode) by producing ketones in the liver to convert stored and consumed fat into energy. But what does a ketogenic diet (almost entirely absent of carbohydrates and sugar) mean for the brain, the most vital of all organs--and notorious for its glucose consumption?
What Does a Ketogenic Diet Do to Your Brain?
The answer to this question really depends on how recently you’ve begun a ketogenic diet.
If your brain and body are used to running on a steady stream of glucose, suddenly pulling the plug by eliminating carbohydrates can be difficult. The notorious “keto flu” is the name many people use to describe the withdrawal symptoms you may experience as your body tries to convince you that it really wants that sugar back--the sugar it’s been taught to expect as part of the standard American diet.
You might experience a “brain fog,” difficulty concentrating, irritability, low energy, or intense cravings for anything sugary or carbohydrate-heavy.
Thankfully, however, this keto flu doesn’t last very long. And waiting on the other side is a whole host of brain benefits (more on that below). It’s also worth mentioning that a few simple tips can make the transition to ketosis a lot easier--like keeping a close eye on electrolytes, taking exogenous ketones (ketones in supplement form that help your body turn fat into energy), and staying very hydrated.
As you stay the course and cut out sugar in favor of fat, your body uses up its stores of glycogen, and a fascinating rewiring takes place. You begin to process energy in a new way--especially in your glucose-loving brain. The lack of consumed sugar triggers your body to produce ketones in the liver, which in turn allows you to create energy from stored and consumed fat. It’s the same process that happens when you fast for a period of time.
Interestingly enough, your brain doesn’t use the energy from fat +ketones the same way it uses the energy from sugar. If you maintain a ketogenic diet, the process of becoming “fat-adapted” actually causes your brain to create totally new energy-processing pathways. Scientists believe that this is one of the main reasons a ketogenic diet can cure epilepsy: the brain is literally able to rewire itself using a new, cleaner, and more sustainable source of energy.
But the brain-benefits of a ketogenic diet aren’t restricted to epilepsy:
Brain Benefits of a Ketogenic Diet
As the body adapts to using fat and ketones for energy, a surprising number of brain benefits emerge, including the following:
Several studies have found that ketones act as antioxidants, which can protect the brain from oxidative damage and free radicals.
For brain cells that are damaged, aging, or otherwise compromised ketones can also act as a cleaner, more efficient source of energy than glucose. In other words, cells in the brain that struggle to function optimally using glucose as an energy source are able to regain functionality and even thrive using fat as an energy source. Keto’s neuroprotective properties have been extensively studied as they relate to epilepsy. And the ketogenic diet has been also been the subject of numerous promising studies related to neurodegenerative diseases like Alzheimer’s and Parkinson’s, as well as ALS, brain cancer, stroke, traumatic brain injury, and autism.
Improved Cognition, Memory, and Focus
With ketones as its primary energy source, the body can improve the quality of its mitochondria. These important organelles found inside cells have been inseparably linked to neurodegenerative diseases and impaired cognition when damaged. On the flip side, fortifying the mitochondria allows the human brain to work more efficiently and effectively, resulting in improved cognition and focus.
Ketones also improve cognition, memory, and focus by decreasing glutamatergic tone while simultaneously increasing GABAergic tone. Glutamate and GABA are two neurotransmitters in the brain that are crucial to memory, higher thinking, However, the balance between these neurotransmitters is very important to brain function. Imbalances in glutamate and GABA can lead to ALS, MS, or even Alzheimer’s. Ketones optimize the balance between these neurotransmitters, allowing them to work in tandem properly and enhance memory, focus, and cognition.
Boosts Learning Capacity and Higher Thinking
Researchers have pinpointed the protein BDNF (brain-derived neurotrophic factor) as one of the keys to learning and higher thinking. BDNF has been called “Miracle-Gro for neurons,” allowing these cells to thrive, grow, and make new connections with one another in the brain--the foundation of learning and higher thinking. BDNF also creates the pathways that allow neurotransmitters like dopamine and serotonin to travel between neurons, and improves the quality of the connection in these interactions. Ketones facilitate higher levels and expression of BDNF.
More Consistent Cognitive Function and Mood
Most of us know the feeling of being hangry, or having a hard time thinking because we’re hungry. However, once the brain has adapted to using ketones as a primary fuel source, these dips and peaks in mental function and mood all but disappear. Whether from consumed fat or stored adipose tissue, the brain now has a consistent and reliable fuel source that can keep moods and thought processes stable.
Brain-Related Keto Myths
Despite all the brain benefits the ketogenic diet has to offer, several myths persist. While there are some legitimate risks of a ketogenic diet as related to the brain ((more on this below), these three urban legends shouldn’t deter you from trying keto:
Myth #1: Keto Contributes to Metabolic Dysfunction and Insulin Resistance
This mythbuster comes with a caveat: While a ketogenic diet won’t cause metabolic dysfunction, adapting to using ketones for fuel instead of glucose does mean that eating a piece of cake will be harder on your body than it would have been pre fat-adaptation. Your cells, now adapted to primarily using fat, aren’t the sugar-processing factories they once were. Essentially, they’ve been taught to leave any extra glucose for your brain (rather than your muscles). Throw a large dose of sugar at those cells--with the accompanying insulin spike--and it shouldn’t be much of a surprise to find that those cells aren’t quite as quick on the uptake.
On the other hand, the keto diet has been shown time and time again to improve insulin sensitivity. In other words, cells on a keto diet become much more efficient and at using smaller amounts of glucose and insulin effectively.
Myth #2: The Brain Has to Run on Glucose
We’ve already partially covered this one, but this myth is so significant that it’s worth reiterating. It’s true that most Americans’ brains do run on glucose. But that doesn’t mean the brain has to run on glucose. If this were the case, you’d pass out or die as soon as food was restricted. While not ideal by any stretch, the average person can go three weeks without a single bite of food before depleting muscle and fat stores and succumbing to starvation.
With a little adaptation to the ketogenic diet, the brain can happily (and sustainably) get 75% of its required energy from ketones and fat (both stored and consumed). The other required 25% comes from protein and a small amount of carbohydrates.
Myth #3 Keto Causes Hippocampus Shrinkage
It’s true that the keto diet has an impact on the hippocampus--but not in terms of shrinkage. Evidence shows that the keto diet causes changes in hippocampal excitability (which can actually be neuroprotective) and even helps restore impaired hippocampal memory in mice; however, there’s not a shred of evidence that the keto diet shrinks the hippocampus or any other part of the brain. The standard high-carb American diet on the other hand--studies show that it does shrink the hippocampus, literally causing brain damage.
Brain-Related Risks of a Ketogenic Diet
Most of the risks associated with a keto diet are either very temporary, rare, or completely avoidable if enough protein is consumed:
As mentioned above, a “brain fog” (also known as “keto brain”) can be a temporary side effect during the adjustment period. Don’t worry--it’s not serious. And it will go away. Using ketones instead of glucose as a primary energy source can mean that you’re not at the top of your game mentally for a few days--unless you supplement with exogenous ketones to provide your brain and body with energy while your own liver gets with the program and starts producing ketones.
Muscle Depletion to Supply Brain Glucose
Eating enough protein is very important on a keto diet. Ketones can supply about 75% of the brain’s energy needs, but that remaining 25% is still critical. Your body can get this glucose from consumed protein through a process called gluconeogenesis--or it can take that protein from your muscles through the same process (after all, your muscles are protein!). You’ll need to eat at least 40-50 grams of protein per day, 20-25% of your daily macronutrients.
First things first: Ketoacidosis is not a risk for most people (you can read more about the difference between nutritional ketosis and ketoacidosis here). But this condition, where blood sugar AND ketones are very high, causing a sustained chemical imbalance in the blood, can be very serious for a small subsection people with undiagnosed diabetes or insulin production problems. If you feel confused and lethargic combined with flu-like symptoms while on keto, seek medical attention.
Keto is a unique diet--especially compared to the standard American diet. And its benefits for the brain and body are just as unique. While it’s important to follow the ketogenic diet correctly to avoid risk (like any diet plan!), the potential for improved cognitive function, neuroprotection, memory, and mood stabilization is incredible--and completely attainable.