A study suggests that the increased cancer risk associated with high fructose intake is caused by the liver’s overproduction of lipids used by cancer cells for growth.
Due to the well-documented effects of excess sugar on increasing the risk of obesity and several cardiometabolic diseases, the World Health Organization recommends limiting the consumption of free sugars to less than 10% of intake. daily energy, which corresponds to approximately 30 g or 7 cubes of sugar.
This recommendation unfortunately remains little followed: in Canada, for example, the consumption of foods rich in free sugars (sweetened drinks, snacks, desserts and pastries, in particular) is very high and leads to an average intake of more than 100 g of sugars. free per day, more than three times the suggested maximum amount.
Fructose and glucose, two very different sugars
The two main forms of free sugars consumed are sucrose and enriched fructose corn syrup (high fructose corn syrup or HFCS).
Both consist of a mixture of glucose and fructose, but in different proportions: while sucrose is made up of 50% glucose and 50% fructose, HFCS instead contains 45% glucose and 55% fructose. .
Since fructose has a sweeter taste than glucose and is less expensive than the latter, HFCS is very often used in the manufacture of industrial foods, particularly sugary drinks.
Even though glucose and fructose have the same chemical formula (C6H12O6), they have very different structures which greatly influence how they are metabolized.
While glucose is easily absorbed by the intestine and transported into the blood to be used as an energy source by all of the body’s cells, fructose is mainly accumulated in the liver, where it is transformed into fat.
In the event of excessive food intake, as is the case in obese people, the quantity of fat in the liver becomes too high and can cause hepatic steatosis (this is the principle which is at work when the birds are force-fed with a food rich in fructose [le maïs, par exemple] to produce foie gras).
This abnormal accumulation of liver fat is very inflammatory and can increase the risk of liver disease, type 2 diabetes and hypertension.
-A boost for cancer cells
Fructose has often been reported to be carcinogenic in laboratory animals, but this effect remained mysterious given that:
1) more than 95% of ingested fructose does not reach the bloodstream and therefore cannot serve as an energy source for cancer cells;
2) Most cancer cells do not have the enzymes necessary to use fructose as fuel to support their growth.
Surprisingly, a recent study suggests that it is rather the overproduction of fat in the liver in response to excess fructose which is responsible for this pro-cancerous effect. (1)
The researchers observed that adding excess fructose to the diet (in the form of corn syrup) caused a very significant increase in the blood levels of a class of fatty acids (lysophosphatidylcholines) which are used by the body. subsequently by cancer cells to produce the cell membranes essential for their growth.
In other words, even though it has no direct interaction with cancer cells, fructose still manages to actively participate in the progression of cancer due to the metabolic disturbances it causes in the liver.
Reducing added sugar intake is therefore not only a good way to maintain normal body weight, but also to avoid creating conditions conducive to the development of cancer.
Carefully reading the labels of industrial food products is therefore an important aspect of preventing chronic diseases.
(1) Fowle-Grider R et coll. Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer. Nature 2024; 636: 737-744.
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