What harm can 15 grams of sugar cause

NUTRITION: What sugar does to our brains

NUTRITION: What sugar does to our brains

Sweets are not only bad for teeth and body, but also for the brain. New studies show: Too much sugar can make you depressed and forgetful.

Michael Baumann

The human brain has a special relationship with sugar. It answers before we even put a piece of candy or a piece of chocolate in our mouths. Because just the sight of something sweet activates the so-called reward center in the brain. This announces: "An excellent choice, put it in!" When the candy lands on the tip of the tongue, the sensory receptors begin to fire their signals into the brain. This rewards us for the sweet bite with feelings of happiness. And it demands: "More of it!"

Such beautiful moments bring us sweet things - in the long run, not only figure and teeth suffer, but also mental health. This is shown by a study published last month: Scientists from London University College show a connection between sugar consumption and the development of mental illnesses such as depression and anxiety disorders. This conclusion was based on surveys of over 8,000 study participants on their sugar consumption and psychological well-being. The surveys were repeated regularly over a period of over 20 years. A connection was particularly evident in men: those who consumed more than 67 grams of sugar daily through soft drinks and snacks had a 23 percent higher risk of developing a mental disorder than subjects who did daily five years after the first survey ate less than 40 grams of sweets.

The British researchers believe that sugar consumption actually leads to brain damage and not the other way around. Because those who suffered from a mental disorder at the beginning of the study did not consume more sugar than before five years later.

Correlation between blood sugar and dementia

Earlier studies suggested the negative impact of sugar consumption on the human brain. In 2013, US researchers found that people with high blood sugar levels were more likely to develop dementia. And in another study from the same year, German scientists measured the blood sugar of 141 healthy seniors and then had them take part in a memory test. The subjects had to memorize 15 words. Half an hour later they were interrogated. Again, those subjects who had high blood sugar values ​​performed worse: They remembered an average of two words less than their colleagues with normal blood values. And the examination of their hippocampus - the brain area that helps to store what they have learned - showed that it was smaller and less structured than in the participants with lower blood sugar.

It seems paradoxical: Sugar is said to be harmful to our brain in the long term, and yet it rewards us with happiness hormones for every treat. “Our brain doesn't do anything wrong,” says Matthias Wyss, who researches human sugar metabolism at the Institute for Pharmacology and Toxicology at the University of Zurich. "Sugar is absolutely vital for the brain." In the form of glucose, it supplies our central thinking organ with energy. And it needs more of it than any other organ in our body. Every day it processes around 120 grams of the sweet substance - that's the equivalent of 30 sugar cubes. "In order to have a sufficient blood sugar level, we don't need to eat sweets," says Wyss. Because long chains of sugar are also contained in foods rich in carbohydrates - for example in bread, rice and pasta. Our digestive system splits these long chains into individual glucose molecules, which are then absorbed into the blood. And if the blood sugar drops between two meals, the body can even produce it itself: it mainly converts protein breakdown products into glucose in the liver.

Sugar's accomplices

Although there is a connection between sugar consumption and mental disorders, according to several studies, says Wyss: "The sugar itself is not harmful to the brain cells." Rather, he blames various indirect consequences of sugar for problems such as depression or poor memory. For example, the fat that the body makes from excess sugar. "This leads to changes in the blood vessels and thus to circulatory disorders in the brain, which can explain poor memory performance," says Wyss. He names insulin as another possible culprit. This hormone is secreted by the pancreas when blood sugar levels rise. It ensures that the cells in the tissue absorb the sugar. In the brain, however, it has other functions: It is involved in thought processes and plays a role in memory. If someone eats a lot of sweet things, they have consistently high insulin levels. This leads to habituation - the brain no longer responds properly to the signals. At least in animal experiments, this leads to weaker mental performance. “It is easy to imagine that the same effect will also occur in humans,” says the Zurich researcher.

More research is needed before we understand exactly what sugar is doing in our body, says Wyss. And he himself won't be averse to the sweet stuff for the time being. Because sugar - enjoyed in moderation - also has its good sides: "In the short term, a piece of chocolate boosts memory," says Wyss. So: an excellent choice, put it in!