Glucose is the essential metabolic fuel for the brain. Acute and severe reduction of brain glucose leads quickly to impairment of cognitive and reflex function, autonomic failure, seizures, loss of consciousness, and permanent and irreversible brain damage and, if not rapidly corrected, can be lethal.
“The brain is dependent on sugar as its main fuel,” says Vera Novak, MD, PhD, an HMS associate professor of medicine at Beth Israel Deaconess Medical Center. “It cannot be without it.” Although the brain needs glucose, too much of this energy source can be a bad thing.
Hypoglycemia and the Brain
Symptoms of low blood sugar may include feeling dizzy, shaky, or irritable, and you may have trouble walking or talking. Severe low blood sugar can cause you to pass out or have seizures. It can even put you in a coma.
The energy needs of the brain
A normal weight adult requires 200 g of glucose per day, two-thirds of which (about 130 g) is specifically needed by the brain to cover its glucose needs. The brain competes with the rest of the body for glucose when levels dip very low — such as during starvation.
When we eat sweet foods the brain's reward system — called the mesolimbic dopamine system — gets activated. Dopamine is a brain chemical released by neurons and can signal that an event was positive. When the reward system fires, it reinforces behaviours — making it more likely for us to carry out these actions again.
Focusing on a healthy diet and giving up sugar entirely can go a long way towards increasing your energy levels, improving your memory and allowing you to concentrate more clearly.
Experts say reducing the amount of sugar in your diet is difficult at first (yes, “sugar headaches” are a thing) but if you can hang in there for a few days the cravings, and headaches, will subside. Studies show that most people who stop eating sugar and other processed foods feel less depressed and anxious.
Glucose is the essential metabolic fuel for the brain. Acute and severe reduction of brain glucose leads quickly to impairment of cognitive and reflex function, autonomic failure, seizures, loss of consciousness, and permanent and irreversible brain damage and, if not rapidly corrected, can be lethal.
Sometimes, a low-carb diet can change the body's metabolic process and can hamper mental and physical health. However, excess carbohydrate is bad for our health but survival without carbohydrate is not possible.
Besides killing the brain cells, too much sugar in the brain can also cause slowed cognitive function and even memory and attention problems for seniors. Furthermore, it weakens and damages the blood vessels, which again leads to a declining mental capacity.
It's during this early “sugar withdrawal” stage that both mental and physical symptoms have been reported – including depression, anxiety, brain fog and cravings, alongside headaches, fatigue and dizziness.
The mammalian brain depends on glucose as its main source of energy. In the adult brain, neurons have the highest energy demand [1], requiring continuous delivery of glucose from blood.
Sugar cravings are often caused by imbalances in blood glucose levels. Low blood sugar levels might cause you to crave something sweet in order to bring up these levels. Other factors that can play a role include psychological stress, medications, hormone imbalances, and health conditions.
Our bodies use glucose as a primary fuel source, so our brains have evolved to like sweet foods. Consuming sugar activates the mesolimbic dopamine system, which is the brain's reward system. Dopamine, the feel-good chemical messenger, is then released and reinforces our desire for sugar.
In addition to releasing dopamine in the brain, sugar also releases endogenous opioids. These are responsible for the wonderful surge of pleasure you feel when you eat a piece of candy.
Severe carb limits can cause your body to break down fat into ketones for energy. This is called ketosis. Ketosis can cause side effects such as bad breath, headache, fatigue and weakness. It's not clear what kind of possible long-term health risks a low-carb diet may pose.
Our brain and red blood cells rely on the plentiful glucose in carbohydrates. Through gradual adaptation, the brain can learn to use fat in the form of ketone bodies, but our blood cells will always rely on glucose.
It's true that the brain can't run entirely on ketones; it needs some glucose as well. However, your brain isn't in any danger on a very-low-carb diet or even a diet that's entirely carb-free. Thanks to gluconeogenesis, your body will reliably produce and provide your brain with all the glucose it needs.
Some high-protein diets limit carbs so much that you might not get enough nutrients or fiber. This can cause problems such as bad breath, headache and constipation. Some high-protein diets allow red meats, processed meats and other foods high in saturated fat. These foods may increase your risk of heart disease.
The human brain is nearly 60 percent fat. We've learned in recent years that fatty acids are among the most crucial molecules that determine your brain's integrity and ability to perform.
Insulin is an important hormone that can be found in high concentrations in the human brain. Insulin has been shown to play many different roles within the brain, ranging from neuroprotective effects to positively influencing higher cognitive processes.
Eating a lot of refined, added sugars can lead to headaches, low energy levels, and inflammation. Cutting sugar out of your diet will likely decrease inflammation, boost your energy levels, and improve your ability to focus.
You'll Feel Lighter, Brighter, and Happier
The underlying chronic inflammation that happens when we eat a high-sugar diet negatively impacts our brain function — one of the reasons we get blue with too many sweets.
After you eat a sugary snack, your blood sugar levels spike and you may experience irritability or brain fog. When your blood sugar levels crash, you may feel anxious, tired, and moody.