Eat fruit – but avoid fruit sugar


“Fructose is a poor source of energy for muscle cells”

Is it true that fructose is dangerous for the body? Should you so, avoid eating fruit   ?

Answer: Although fructose is called fruit sugar, one should not believe that it comes from fruit. There is rarely large amounts of fructose in fruit. Do you eat 500 grams of fruit, you just get yourself in a few tens of grams of fructose. This small amount of the body can handle – it is not dangerous.

Our largest source of fructose is plain white sugar, which consists of a part glucose and one part fructose. When we were in the 1800s learned to produce sugar from sugar beets, sugar suddenly became available in much larger quantities. Never before in human evolution, we have eaten so much sugar. The body is not designed to handle it. A major problem is the fructose. In recent years, the industry has also begun producing sweetener fructose-glucose syrup and pure fructose. Starch is digested into glucose, whereupon a part of the glucose is converted to fructose by means of enzymes. For the food industry has two advantages over the syrup with white sugar: it is cheaper and slightly sweeter. Syrup is a common ingredient in such sweets and ice cream. Five full-sized candy pieces contains just as much fructose as 500 grams of fruit. Normally, we do not buy five candy pieces, but rather 300-400 grams.

Why is fructose a problem? Let us compare with glucose, a sugar that we are accustomed to, as long as we have eaten starchy foods like potatoes, rice and bread. When the cell takes up glucose from the blood sugar is broken down by the so-called glycolysis and becomes energy. But if the body does not need energy right then glucose rather than stored as glycogen, the body’s equivalent of starch. Muscle cells store glycogen for its own needs, and liver glycogen stores for the rest of the body. As energy demand increases drop out liver glycogen as glucose in the blood. The reaction of glucose is thus regulated in the body.

What if, instead, we supply the blood with fructose? To begin with, it’s basically just living cells that effectively addresses this sugar. Fructose is a poor source of energy for muscle cells. Furthermore, ducking fructose past the body’s regulation of glycolysis fructose begins to break down regardless of whether the body needs energy or not.

In our modern society, the body suffers rarely loss of energy and then the liver produces fatty acids  instead from fructose. It is formed fats called triglycerides, which goes into the blood and stored in the particular fat cells. In textbooks, it is often that the body converts fructose to glucose. But that only happens if the liver cells are blank on glucose, which they rarely are. We eat almost always glucose and fructose simultaneously. It leads to an unregulated production of fat.

Problems with fatty liver have increased dramatically, which can be explained by the liver has to take care of anything more fructose. The liver fat production also increased blood fats, high levels of triglycerides. This is linked to abdominal obesity and type 2 diabetes. So, yes, the fructose in large amounts is dangerous for the body. But it’s candy, soda and other sweets that are the problem – not the fruit. Fruit provides us with essential vitamins.

Lars-Gunnar Franzen, professor of chemistry at the University of Halmstad.

from article in Swedish


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