For a long time, fructose has been referred to as “fruit sugar,” which associated it with a certain image of a healthy sugar. In addition, it was the type of sugar recommended for diabetics, as it hardly raised insulin levels.
However, in recent years, fructose has shown its darker face, mainly because its effects on metabolism and the brain have been discovered. Furthermore, because the consumption of fructose, through the common sugar of which it is a part, has skyrocketed around the world, with very negative consequences for health.
a cheat gift
Plants produce their fruits not because they have a generous heart, but because they care. Animals, especially mammals and birds, eat the fruit and spread the seeds. To attract animals, the fruits are brightly colored and contain sugar, easy energy.
The simplest sugar is glucose, but the problem is that when an animal (including us) eats enough glucose, it fills up and stops eating. So there’s a catch to the sweet gift of plants: fructose.
Fructose has the effect of deactivating appetite control mechanisms, much more so than glucose. On the one hand, it makes cells resistant (“deaf”) to leptin, the satiety hormone, and on the other, it increases levels of ghrelin, the hunger hormone. The result is that we do not stop eating.
On the other hand, fructose induces insulin resistance. In fact, in the lab, rats on a fructose diet become “diabetic” in just three months. Having insulin resistance means that the cholesterol and triglycerides in the blood are increased, and there is more accumulation of body fat.
As if that weren’t enough, most of the calories in fructose are converted to fat. Fructose is processed in the liver, where it can be converted to glucose to replenish the liver’s own glycogen stores. However, these reserves are usually full because we eat bread, pasta and potatoes every day, which are sources of glucose. With full reserves, all fructose is converted to triglycerides, meaning that the effect of fructose is similar to that of eating fat.
Fructose, Microbiota and the Brain
In addition, consuming large amounts of concentrated fructose (that is, every time we eat sugary foods or fruit juices) alters the composition of the intestinal microbiota, in this case for the worse. They increase the bacteria that induce obesity and reduce the intestinal wall protecting and anti-inflammatory functions. It increases intestinal permeability and causes inflammation.
Finally, fructose also has an effect on the brain. Fructose induces insulin resistance in neurons, so they cannot absorb as much energy from glucose. It affects memory and mental abilities, and inhibits the formation of new neurons in the hypothalamus.
All this can make us think that nature is conspiring against us. Plants provide us with a substance, fructose, poisonous fruits that make us eat without measure, gain weight, become resistant to insulin and be a bit foolish.
However, there was a time when all this was beneficial. Fruit (and honey, another source of fructose) were only available at the end of summer, and at that time it was a good idea to store body fat to survive the winter.
Today, however, we have access to fruit all year round. The common sugar present in almost all processed foods is 50% fructose or more, as in the case of corn syrup. The same goes for natural substitutes that are presented as superior to sugar and actually contain sugar. The first temporary abduction of our bodies by fructose, and the exchange of favors between plants and animals, has become a permanent condition for many humans, and it is affecting health.
Interestingly, the negative effect on the microbiota occurs only with refined sugars and not with the consumption of whole fruit pieces. From the interpretation it appears that fruits do not contain only sugars. On the one hand, the fiber in fruit is satiating and counteracts the effects of fructose. In addition, especially in their skin and seeds, fruits contain various substances that they use as protection against insects and other pests, many of which contain antioxidants such as anthocyanins and vitamin C.
These substances are responsible for the beneficial health effects of fruits, despite the sugar they contain. But keep in mind that the same benefits can be obtained from vegetables.
