How Does Sugar Affect the Brain?

Last update: June 30, 2025

From the Paleo diet to the Mediterranean diet to the ketogenic diet and beyond, there’s one thing that nearly all modern diets agree on—if you want to maintain a healthy body and mind, cut out sugar. 

While there’s wisdom in this advice, blanket statements like “cut out sugar” can leave room for confusion. It leaves many people wondering, is all sugar bad for you? Should you avoid sugar in any form, including in fruits? What about carbohydrates found in fruits and vegetables?

With so many complicated questions like these and no clear answers, it’s no wonder many people feel confused. As a center dedicated to improving brain health and performance, Aviv Clinics understands the importance of proper nutrition and its direct effect on cognitive and physical functioning. 

Let’s examine sugar in detail and clarify what dietitians mean when they tell you to “cut out sugar.”

Is All Sugar Bad for Your Brain? Understanding Natural vs. Refined Sugar

Not exactly—foods with high amounts of sugar can still be healthy. For example: 

• While apples contain lots of sugar, they also supply water, vitamins, nutrients, and dietary fibers that are vital for a healthy body. Dietary fiber is essential for maintaining a thriving wealth of gut flora. Gut flora builds our immune system and fights off ailments like leaky gut disease.
• You can find natural sugars in many whole foods. They also come in many different chemical forms, including glucose from carbohydrates. Glucose provides our bodies with energy, helping fuel our muscles and vital organs as it circulates throughout the bloodstream. We wouldn’t be able to function normally without the glucose we gain from consuming carbohydrates.

Does The Brain Need Sugar to Function? Glucose and Brain Health

Although the brain can use alternative fuel sources, such as ketones, for fuel if you’re insulin resistant, glucose is the brain’s preferred fuel source. The brain relies heavily on glucose when performing complex tasks. 

So when you’re concentrating extra hard on a crossword puzzle or a complicated passage in your favorite book, your brain is burning glucose over time to help you get the job done. If your blood sugar dips too low, you can experience problems like brain fog or trouble concentrating. It’s your brain’s way of telling you that it needs more fuel and that you should grab a healthy snack.

 

Natural Sugar vs. Refined Sugar: What’s Healthier for Brain Function?

While natural sugar naturally occurs in foods, refined sugar is a processed substance. 

How the Body Processes Natural Sugar

When you eat an apple, your body does all the work of processing the unrefined fruit into digestible nutrients all on its own. 

First, you must chew the apple, breaking it down into apple sauce. Then, your gut does the hard work of absorbing the vital nutrients and breaking down the sugar to circulate it through your bloodstream. 

The leftover fiber is used to nourish your gut’s network of microflora. When you eat whole foods, your body is the factory, and the natural sugars in your foods are the fuel that runs it.

What Refined Sugar Does to Your Body and Brain

Foods with refined sugar are a different story. Candies, cookies, chips, and other pre-packaged snacks don’t offer your body the same fuel as whole foods. Your body doesn’t have to go through the work of breaking down these highly processed foods—the factory already did it for you.

Processed foods are loaded with refined sugar without any of the nutrients, vitamins, and fiber your body needs. This leaves your gut flora starved of the materials required to function and your immune system vulnerable. 

How Too Much Sugar Affects the Brain and Cognitive Performance

It’s possible to have too much of a good thing. Modern Western diets are filled with refined sugar and carbohydrates in the form of ready-made snacks, treats, and processed foods. 

Thus, you may feel sluggish once the “sugar high” wears off. Eating too much sugar can also make you susceptible to health conditions like type 2 diabetes.

The best way to limit refined sugar intake is to lean on a natural diet consisting of whole foods.

Sugar and the Brain: Effects on Memory, Mood, and Brain Fog

Excessive sugar intake can impact specific neurotransmitters and bring on memory deficiencies. Among these neurotransmitters is dopamine, the chemical controlling mood, behavior, learning, and memory.

Here’s what research studies further illustrate: 

• When rats were fed a high-sugar diet that resembles the average Western diet, their cognitive performance suffered. The rats struggled to complete tasks that relied on their memory. Their struggles suggest their diets were directly responsible for impairing their brains’ prefrontal lobes and hippocampus regions.
• Eating a diet high in sugar can reduce the production of a chemical called “brain-derived neurotrophic factor” (BDNF). This chemical is active in areas of the brain vital to learning, memory, and higher thinking. Low BDNF levels are associated with poor memory function and are linked with Alzheimer’s Disease and dementia. 
• Experiments in both laboratory animals and humans have revealed that when the brain needs an extra power boost, blood vessels in the brain dilate to deliver more glucose and oxygen through the bloodstream. 

 

 

Why the Brain Needs Glucose (And How to Get it From Healthy Foods)

Yes, natural sugars perform a vital role in energizing the body and mind. The body requires a total of 200 grams of sugar or glucose each day. Two-thirds of this, or 130 grams, is used by the brain to help you function to your best ability. 

The key takeaway from the information we presented above is this: incorporating a diet filled with natural, whole foods is essential to: 

• Nourishing your body with the right type of sugar
• Enhancing cognitive and physical performance 

4 Smart Ways to Reduce Refined Sugar and Improve Brain Health

The natural sugars found in whole foods are nothing to fear. Eating a diet with enough carbohydrates and natural sugars is vital for keeping your body and brain healthy. 

Here are a few ways to stay on track:

1. Make sure the bulk of the sugar you consume comes from whole foods like fruits and vegetables, not processed junk foods.
2. Just because a food is labeled “sugar-free,” that’s not always the case. It may be true that a food doesn’t contain added sugar, but remember that carbohydrates turn into glucose in your body.
3. You can rack up carbohydrates quickly on a typical day. Try to aim for around 45 total carbs at every meal if you’re a woman or 60 at every meal if you’re a man. You’ll be surprised how quickly you can meet that quota with just a handful of whole foods!
4. You don’t have to cut out refined sugar altogether. Obsessing over eating a “perfect” diet only stresses you out and doesn’t leave any room for you to feed your soul. Do you plan on spending a relaxing afternoon baking with your grandkids? Go ahead and treat yourself to a warm cookie fresh from the oven.

If you’re eating healthy at most meals, there’s no need to feel guilty about indulging in rich foods now and then. Just be smart about it, and always make conscious decisions about what kind of foods you put into your body.

Enhance Brain Performance With the Aviv Medical Program

Aviv Clinics delivers a highly effective, science-based treatment protocol to enhance brain performance and improve the cognitive and physical symptoms of conditions such as traumatic brain injuries, fibromyalgia, mild cognitive impairment, long COVID, and others. The Aviv Medical Program’s intensive treatment protocol features Hyperbaric Oxygen Therapy and can include interventions like nutrition management and support for better brain health. Based on nearly two decades of research and development, the Aviv Medical Program is customized by our physicians to meet your needs.

Contact us to speak with a Client Ambassador about the Aviv Medical Program