Why is glucose essential for brain function?
Glucose is the main fuel that provides energy to the body’s cells and the neurons of our brain which, like that of all mammals, needs a constant supply of glucose to function.
Despite this reality, the WHO recommends reducing the consumption of sugar below 10% of the total caloric intake of the day, and even encourages this consumption to drop 5%, because “it would produce additional benefits for health”.
The food industry has been reformulating their products to reduce sugars, in addition to salt and saturated fats. Why, if glucose is essential for brain function, does it not help us to eat sugar?
Yes, the brain eats glucose
Glucose is an organic compound very common in nature, a form of sugar formed by large molecules that, through what is called catabolic oxidation, is transformed into smaller and simpler molecules, a process that releases an important amount of energy that is used to carry out the set of chemical and physicochemical reactions that take place in all the living cells of the organism: metabolism.
The brain consumes 5.6 milligrams of glucose per 100 grams of brain tissue per minute. In the brain of an adult individual, the greatest demand for energy comes from neurons. For them, glucose is essential because unlike the common cells, which also get energy from other sources, neurons practically depend on this substance.
Therefore, despite the fact that the brain represents less than 2% of body weight, it spends up to 20% of the total glucose energy produced by the organism: it is its main consumer.
Where does glucose come from?
Glucose is an essential component for life, and specifically for the proper development of brain functions. However, even if it is a simple sugar or monosaccharide, you do not have to take sugar or sweet foods so that the body has the necessary amount, an argument that is frequently used by the food industry to justify the inclusion of sugars in the products that they market.
In fact, if a person adopts a sugar-free diet, it would not be a problem: the body has several mechanisms to obtain glucose.
In addition to obtaining it through food, our body can synthesize it from glycogen, a polysaccharide stored in the liver and, to a lesser extent, in the muscles.
Glucose is also generated from waste products of fats called ketone bodies, which, in situations of low blood sugar content, can make up for that lack of it.
Other sources of energy are fatty acids. Fat is stored in the form of triacylglycerides, one molecule of glycerol and three of fatty acids. In humans, fatty acids cannot cause glucose but glycerol does, although in minimal amounts.
You have to eat the right amount
In short, all the food we eat ends up being reconverted, to a greater or lesser extent, into glucose or energy for the organism.
In particular, the most easily reconverted type of food is the carbohydrate group. These include the free sugars that are added to countless products, but also many others, such as cereals, legumes, dairy products, fruits and vegetables.
If we have a healthy diet and our body works well, there is nothing to worry about: the glucose contribution is guaranteed, even if we do not take cupcakes any more. The evolution of having resources to obtain the main contribution of cellular energy has already been occupied.
But, as is known, the organism can fail for multiple reasons, also in regard to obtaining glucose.
When the contribution is not necessary, that is, when the amount of blood glucose is excessive or insufficient, there is, respectively, hyperglycemia and hypoglycemia.
Diabetes is one of the most widespread causes of this dysfunction and is due to the insulin resistance of those affected by this disease.
Insulin is the hormone that regulates the amount of glucose in the blood. If it does not work, it can trigger both hyperglycemia and hypoglycemia, and the consequences of this are all negative.
High levels of permanent blood glucose can cause damage to various organs of the body, such as the retina, the kidney, the arteries or the nervous system. On the other hand, low glucose levels can even lead to a diabetic coma and the death of the patient.
If glucose is scarce, several dysfunctions and pathologies appear, as evidenced by a study carried out by researchers from universities and research centers in Germany and the United States.
The metabolism of glucose provides the fuel for the physiological function of the brain through the generation of adenine triphosphate, the star molecule in the process of obtaining cellular energy in chemical reactions, the basis for neuronal cell maintenance and not neuronal, as well as the generation of neurotransmitters.
If the metabolism of glucose is altered, several neurological alterations can arise, as well as obesity, type 2 diabetes, dementia, or Alzheimer’s: precisely, one of the earliest signs of this disease is the reduction of metabolism of cerebral glucose.
If neurons cannot get the glucose they need, it can trigger even a process of cell death by autophagy, by not having the food they require to function, these brain cells get the energy of themselves to death.
When glucose levels are below what is necessary, the neurons activate a series of warning signals that send to the body as a whole: vision problems, irritability, anxiety, sweating, dizziness, drowsiness, confusion, weakness, hunger … a collection of messages that cause the person to correct this lack of glucose by ingesting food.
If the glucose does not increase, seizures, fainting or even a coma can occur, which could end with a neuronal death. On the other hand, the symptoms of hyperglycemia, blood sugar higher than 180 milligrams per deciliter, mg / dL, are an excessive thirst, headache, problems in concentration, blurred vision, frequent urination and weight loss.