Carbohydrates are better known in the popular language as sugars. But not all sugars are the same. The first thought that comes to mind when thinking about sugar is the usual household sugar (sucrose), which can be found in drinks and bakery products. Fructose is also very well known and, as its name suggests, is found in fruit. The sugar that is measured to exclude diabetes (blood sugar disease) is blood glucose. There are also many other sugars – just take a look at the nutrition information of a yoghurt or a purchased fruit juice spritzer: added sugar is usually hidden under the suffix -ose or as syrups.
Sugars can be chemically divided into single (monosaccharides), double (disaccharides) and then complex sugars (polysaccharides) based on their number of sugar molecules. This classification refers to biochemical processes such as, for example, the speed of energy production, which is fast in the case of double sugars such as the aforementioned household sugar and the blood sugar level rises accordingly. In contrast, particularly complex sugars first have to be broken down into smaller sugar building blocks by enzymes in order to obtain adequate energy.
The brain is the major energy consumer in the human body (approx. 25% of the total energy consumption). This energy can easily be provided by the blood sugar (glucose). Just 150 years ago, sugar was a luxury good. Pure sugar meant reward and was used for special occasions in fine food. The supply of the body with glucose was ensured at that time by the nutrition from the simple and complex carbohydrates contained in numerous foods. From 1852 until today, however, the per capita consumption of refined sugar in Germany (as in all industrialised countries) has increased almost exponentially. This fact leads to a flooding of the body with sugars mainly in the form of fructose, glucose and sucrose.
To maintain the structure and function of nerve cells, only the monosaccharide (monosaccharide) glucose (dextrose) is required. Within the cell, glucose is converted into the fuel of all cells ATP (adenosine triphosphate). It also provides substrates for cell formation. One could think: as much sugar as possible is supplied and the brain (and all other cells) are full of energy and live happily? Unfortunately this is not true at all.
The crucial point is the path that glucose takes from the blood and the extracellular space into the cell. The magic ingredient for this is the hormone insulin produced by the pancreas – and, as has been known for a few years now, also to a small extent by the brain [Gerozissis 2003]. Each cell has so-called insulin receptors, which ensure that the glucose is transported into the cell – as long as there is no insulin resistance.
Insulin resistance occurs when the sensitivity and response of the insulin receptors are disturbed and altered. Glucose can then no longer be adequately utilised, the blood sugar level rises and, above certain thresholds, the entire organism is immensely damaged. Insulin resistance leads to addictive behaviour (sugar addiction), fatigue syndrome, eating disorders, circulatory disorders and diabetes mellitus type 2.
The cells in the brain can also become insulin-resistant. However, the brain is the body’s largest energy consumer, so a lack of energy is catastrophic for all human cognitive and motor performance. Memory performance, cognitive abilities and concentration are particularly affected. Equally, the increased incidence of depression and dementia [Razay 2007] is closely related to insulin resistance in the brain.
Insulin resistance is further increased by a lack of physical exercise. On the other hand, any kind of physical/muscular activity improves the sensitivity of the insulin receptors and facilitates the transport of glucose into the cell interior. Even serious cases of insulin resistance can be improved by sport and moderate exercise to a greater extent than by drug treatment [Knowler 2002].
But “grey is all theory…”. For those at risk of dementia, these facts provide some important recommendations: