Serotonin: chemistry of the zest for life

Serotonin is a so-called neurotransmitter. Neurotransmitters are messengers that transmit information from one cell to another in the brain. A large number of these chemical transmitter substances are already known. Serotonin influences the sleep-wake rhythm, our sexual behavior, aggression, memory, appetite, anxiety and of course our sense of life.

Tryptophan, sugar and serotonin

Serotonin is formed from a protein building block, the amino acid tryptophan. But before serotonin can be created, the tryptophan must first reach the brain, and that is not at all that simple. Because at the ‘border’ between the blood and the brain it needs a means of transport, a ‘taxi’ that transports it to the brain. And this ‘taxi’ not only transports tryptophan, but also other amino acids. Usually tryptophan is a rarely seen passenger, because our dietary protein contains only one and a half percent of it. That changes when we eat something sweet. Our body then makes insulin available to process the sugar, which quickly flows into the blood. The insulin not only removes sugar from the blood, but also supplies the muscles with amino acids. This causes the level of amino acids in the blood to drop, and there are no longer as many of them pushing the ‘border’ between the blood and the brain to get into the taxi. Tryptophan is an exception. It is retained in the blood so that its concentration remains the same. As a result, the tryptophan can now gather more seats in the ‘taxi’. As a result, more tryptophan enters the brain and more serotonin is formed.When we eat a lot of protein instead of carbohydrates, the exact opposite phenomenon occurs. Then the number of amino acids increases. The little tryptophan has little chance of ending up in the brain. This example shows how complex feedback systems work: if you eat protein, which supplies tryptophan, less tryptophan ends up in the brain than if you eat sugar, which contains no tryptophan at all. In this way, one-sided feeding is prevented. This mechanism could explain why we first eat the tryptophan-containing meat and then the sweet dessert.Very normal components of food, such as sugar in this case, can, if used correctly, ‘set the mood’. That’s why people like to eat sweets so much because it brightens their mood without clouding the mind like alcohol does. That is one explanation why we love sweets so much: once the body has experienced that sugar can increase life satisfaction at least for a while, it craves it more and more often. The subsequent drop in mood does the rest.

Why we eat seasonally

But why do we eat bread with honey or jam for breakfast, and not in the afternoon? Why do we eat much more sweets in winter and autumn than in summer or spring? These questions can also be answered if we take a closer look at brain metabolism.You probably know the feeling: November is coming, and you’re feeling down, tired, and craving something sweet. You reach for marzipan, chocolate and cookies. Of course, this will also cause you to gain a few pounds. And the more you try to sleep off your fatigue, the worse it gets. But take comfort: polar researchers also know the problem. In the polar night they complain of depression and weight gain. In general, this phenomenon – called ‘winter depression’ in medical jargon – occurs much more often in the north of our globe than at the equator. A trip to the sunny south or a skiing holiday in the glittering snow often works wonders.

Light and sugar

What we lack is light. Light and sugar apparently have the same effect on people’s mood. Both indeed affect serotonin metabolism. With one difference: while sugar increases the messenger substance, sunshine prevents its breakdown. Conventional interior lighting, unlike daylight, is not sufficient to stop the decomposition. So it is understandable that people reach for the cookie jar in the dark days before Christmas. Every person strives for a positive attitude towards life and wants to be in a good mood. That’s what we live for. Our actions are aimed at this. Intuitively, we do our best to keep our serotonin levels high. That’s why we eat what we eat.In the spring, when the days become longer and sunnier, our urge for sugar and cake disappears. The drowsiness makes way for a new urge to act, and we then automatically lose a few kilos. That is why there are so many spring diets, but there is no November diet. This is how the appearance of success is maintained. When the light intensity decreases, when dusk falls or when we sleep, the conversion of serotonin into the hormone melatonin begins in the brain. As a result, serotonin levels drop. This is therefore the lowest in the morning. This may explain our craving for jam for breakfast.

Exercise and serotonin

In addition to sugar and light, physical activity also increases the serotonin concentration in the brain. People who go out to jog in all weather conditions want nothing more than those who snack at home: to stay in a good mood at all costs. Winter sports are particularly effective. The snow reflects the light, the physical activity puts the skier in a mild euphoric mood. Athletes and people who do heavy physical work are therefore not in much danger of becoming addicted to sweets. And because the nighttime serotonin breakdown only ends when we get up, there is of course another option to keep the serotonin concentration in the brain as high as possible: getting up earlier. This is good for the psyche, and many depressed people have already benefited from it.In summary: our aim is not to label sugar as ‘innocent’ or to promote its consumption. Sugar is no more necessary than alcohol. We just want to explain why even most critics of sugar crave this sweet substance. Anyone who does not take these connections into account will fail again and again in their attempts to reduce sugar consumption, in whatever form.

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