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Glucose (energy) and learning

Your brain needs much energy. Nerve transmission, or signals passing from one neuron to another, consumes over half of the energy used by your brain. This can be over ten percent of your body’s total energy use. The brain’s neurons consume more energy during learning and other mental activities.

Each neuron takes mainly one form of sugar, glucose, and burns it with oxygen to supply its energy needs. Neurons use this energy to fire when triggered, for growing new connections, and for general cell maintenance.

Neurons cannot store glucose. They can only get it, when needed, from the bloodstream. The hippocampus, one particular area in the brain, suffers when it cannot get enough glucose. As the hippocampus helps sort and store key types of memories, any lack of energy in this area results in less effective learning. Low blood glucose directly affects other areas of the brain as well. For example, low blood glucose results in slower processing of visual and auditory information.

Sources of glucose

Your body gains glucose mainly from the carbohydrates in the foods we eat. The stomach breaks carbohydrates into glucose, which is a simpler carbohydrate. In some foods, the sugar is already glucose and it passes directly into the bloodstream.

So how do you keep up good levels of blood glucose? Eat complex carbohydrates from plant-based foods such as grains, legumes, fruits and vegetables. These provide the best form of carbohydrates because they take time to break down in the stomach. They release their glucose over several hours.

Not all sugars are good for learning

Not all forms of carbohydrates are good for boosting brain performance though. Avoid large injections of sugar such as soft drinks, cakes, chocolate, and other refined sugary foods. While it may seem these should help your brain work well, it’s only a temporary effect. With such a large change in blood glucose, your body releases large amounts of insulin, a compound that regulates the levels of sugar in your bloodstream. The presence of insulin signals various parts of the body to take glucose from the blood.  The body turns that excess glucose into compounds that store the energy for later use. It turns the glucose into fat.

Because these sugars in these foods are short lived, the body soon finds itself with not enough glucose and too much insulin in the blood. This causes large swings between too much and then too little sugar in the blood. These swings result in you feeling tired or spaced out within a few hours after consuming such a food or drink. If you then consume another high sugar snack, off goes the process again. These swings, over time, can reduce your body’s sensitivity to insulin. This can result in diet-induced diabetes.

Key messages

What is the lesson to take away from this? Eat a diet rich in complex carbohydrates from whole grain foods, vegetables, fruits and nuts. Don’t skip breakfast, and don’t “load up” on sugary foods before class and especially not before exams. Before a long exam or other mentally intensive activity, eat a good meal with both proteins and complex carbohydrates. Also, if allowed, take in wholesome snacks that you can eat each hour or so, before you feel hungry.

A last point about brain energy is that eating a large meal can negatively affect brain performance. Glucose gets to the brain via your bloodstream. After eating a large meal, the body diverts blood to the stomach to digest the incoming food. This diversion of blood takes blood away from the brain. This leaves you feeling tired or sleepy (especially after a big Sunday lunch). Avoid eating a large fat- and protein-rich meal directly before class, training, a performance or an exam if you want your brain performing at its best!