Why Does the Brain Require Such a Massive Amount of Energy to Function?

How much energy does the brain actually use? You probably know that your muscles need a lot of energy to power your movements. And it seems obvious that an intense workout would burn more energy than watching television. But the curious thing about your brain is that even though it’s a relatively small organ, it requires tons of fuel. And it uses quite a bit of energy, whether you’re resting, thinking, or even sleeping.

Why does the brain need so much energy? It’s not lifting weights or running, after all.

The short answer is, your brain needs so much energy because it never shuts down and is always working. It also needs a lot of energy because it can’t store fuel.

How Much Energy Does The Brain Use?

For most humans, your brain represents about 2% of your body weight. And yet, it uses about 20% of the oxygen and calories you consume.[1]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC124895/

What’s more, how much energy your brain uses per day doesn’t seem to fluctuate too much — whether it’s making math calculations or at rest. Even when it’s relatively quiet, your brain still needs a constant supply of energy for its day-to-day function.[2]https://www.jci.org/articles/view/103159


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Why Does Your Brain Need So Much Energy?

Since the neurons in your brain use electrical impulses to communicate with each other, experts believe that this process is where the majority of your brain’s energy expenditure lies.

However, researchers estimate about two-thirds of the brain’s energy allocation is used to power neurons. And the remaining one-third is used to perform maintenance tasks — like upkeep of glial cells and neurons.[3]https://www.pnas.org/content/105/17/6409/tab-article-info

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What Are Synaptic Vesicles?

Scientists have also recently discovered that synapses aren’t the only power hogs in the brain.

As it turns out, synaptic vesicles, or neurosynaptic vesicles, use quite a bit of energy, too. Synaptic vesicles are located in the neuron, and they store neurotransmitters like dopamine and glycine — then release them into the synapse.[4]https://www.sciencedirect.com/topics/medicine-and-dentistry/synaptic-vesicle [5]https://www.jneurosci.org/content/39/42/8209 [6]https://pubmed.ncbi.nlm.nih.gov/7700521/​​

These synaptic vesicles are a huge source of energy consumption in the brain. As they pump neurotransmitters in and out, they use up copious amounts of energy. And they aren’t very efficient, either. They appear to be somewhat “leaky” — which means they continue to use energy even if the brain isn’t particularly active.[7]https://www.science.org/doi/10.1126/sciadv.abi9027

How Much Of The Brain Do We Use?

Have you heard the myth that we only use a small percentage of the brain?

That’s a common misconception that continues to circulate. What actually happens is that many of your neurons stay silent, waiting for the chance to wake up. They’re not inactive or dead, they’re just switched off in order to conserve energy. If your entire brain was lit up all the time, the energy draw would be enormous.[8]https://www.ncbi.nlm.nih.gov/books/NBK551718/

What Happens To Brain During Sleep?

Another reason your brain uses so much energy — it doesn’t go to sleep when you’re sleeping. So, the brain never really shuts down. It’s constantly using energy.

While you’re sleeping, the brain performs complex maintenance tasks, like repairing cells, reorganizing neurons, and processing waste.

During sleep, your brain takes short-term memories and turns them into long-term memories. It also works on clearing out information that you no longer need. Basically, sleep is a time that your brain uses to attend to housekeeping functions that can’t otherwise be performed while you’re awake and using your brain for other tasks.[9]https://www.jneurosci.org/content/37/3/464

All of these housekeeping activities require a good bit of fuel to perform.

The processes that your brain attends to during sleep affect your ability to:

  • Learn
  • Be creative
  • Solve problems
  • Make decisions
  • Concentrate and focus

Does Your Brain Use More Energy When Studying

While you might think that your brain uses a ton more energy when studying, learning, or attempting a difficult task — the increase in energy consumption is likely quite minimal.

Researchers have shown that when neurons fire, extra oxygen and glucose get delivered to them.[10]https://pubmed.ncbi.nlm.nih.gov/3265709/ And the brain cells greedily devour the extra nourishment.[11]https://www.sciencedirect.com/science/article/abs/pii/0160289695900179

So, it would make sense, then, to assume that if an active neuron needs more glucose — mental challenges should induce a decrease of glucose in the blood, right? But research doesn’t really back up this hypothesis.

For example, in one study, participants were split into two groups: one group just pressed a key repeatedly. The other group performed complex mental tasks. On the one hand, the complex group did show the expected drop in blood glucose in comparison to the simple group…but the addition of a sugary drink didn’t improve task performance universally. It helped on some tasks, but not others.[12]https://pubmed.ncbi.nlm.nih.gov/11495663/

And then there are studies that suggest those with a higher aptitude for particular tasks use more glucose.[13]https://www.sciencedirect.com/science/article/abs/pii/0160289695900179 Which doesn’t seem to fit with the assumption that the harder your brain’s working, the more energy it’s using.

Overall, it seems that the brain may need additional energy in order to work on complex tasks, but the increased glucose consumption is likely minimal.[14]https://www.sciencedirect.com/science/article/abs/pii/S0014299904002006

The Developing Brain

It’s important to note that all of this talk about the brain’s energy expenditure assume that the brain in question is a fully formed, adult brain.

In fact, while adult brains use up 20% of your energy, a child’s brain consumes over half of the child’s available energy.[15]https://www.karger.com/Article/Fulltext/508054 Since the brain begins developing at a few weeks post-conception and continues evolving and growing into early adulthood, that’s a lot of energy needed over a period of many years.[16]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722610/[17]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989000/

Your Brain Can’t Store Energy

Perhaps the main reason your brain needs so much energy is because it can’t store it. Even though you may think the brain should store energy for emergency metabolic demands…it can’t. Brains require a constant flow of oxygen and glucose in order to function, which means they need blood flow to survive.[18]https://www.ncbi.nlm.nih.gov/books/NBK28194/

Your Brain Is Still Very Efficient

The brain has quite a reputation for being an energy hog.

But when you stop and think about it, the brain is a very efficient and effective machine.

After all, a computer uses about 40 watts of power to run about a billion transistors…and the human brain uses about 20 watts of power to run approximately 500 trillion synapses (which are individually more complex than a transistor).[19]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC124895/ Considering your entire brain is run by less fuel than a typical lightbulb requires…it seems less a hog and more of an elegant energy processor.

Fuel Your Brain The Right Way

When you consider how much energy your brain needs to function properly and maintain itself, it makes sense to give it the most efficient fuel possible.

Your brain needs a steady supply of not only glucose, but also choline, amino acids, and other nutrients to reach peak performance.

And if you’re already struggling with brain-strain issues like brain fog, difficulty focusing, or trouble completing creative tasks…your brain could need even more support.

Take our quiz here to see if nootropic supplements are right for you.

We’ll ask you a few quick questions to determine your baseline and, using our proprietary algorithm, offer you immediate suggestions to help give your brain a new lease on life.

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