Eating a high-fat diet combined with the intake of beverages sweetened with liquid fructose, may be linked to fatty liver disease, according to a study.
Fructose is one of the most common sweeteners in the food industry. This simple sugar (monosaccharide) is industrially obtained from corn syrup, a product derived from this gramineae.
With a great sweetener power and low production costs, fructose is used by the food industry to sweeten beverages, sauces and processed foods, despite the scientific evidence that associates it with metabolic diseases which are risk factors of cardiovascular pathologies.
According to the new study published in the journal Molecular Nutrition and Food Research, the effect caused by fructose in the increase in the synthesis of fatty acids in the liver is more decisive than the external introduction of fats through the diet.
It showed that the accumulation of fats in the liver accelerates and hypertriglyceridemia – a cardiovascular risk factor – can appear.
“In high-fat diets which are supplemented with liquid fructose, this monosaccharide is able to induce an increase in the de novo lipogenesis — that is, the formation of fats through sugar and an inhibition of the lipid oxidation in the liver,” said Professor Juan Carlos Laguna, from the Department of Pharmacology, Toxicology and Therapeutical Chemistry at Fabra University in Barcelona, Spain.
In particular, fructose intake directly causes an increase in the expression of enzymes that control the hepatic synthesis of fatty acids.
The findings showed that the combination of the saturated fat from dietary origin and the induction of the endogen synthesis of fatty acids is what causes the emergence of the fatty liver.
“Moreover, we are describing for the first time that fructose, unlike high-fat diets, increases the expression of the PNPLA3 protein, associated with the appearance of hypertriglyceridemia, a risk factor for cardiovascular diseases,” said Nuria Roglans, from the varsity.
Several epidemiologic studies related the consumption of drinks that are sweetened with fructose to the non-alcoholic fatty liver disease (NAFLD), a pathology for which there is no specific pharmacological therapy.
In these patients, de novo lipogenesis contributes up to 30 per cent of the lipids accumulated in the liver, while in healthy people, this synthesis brings only 5 per cent of hepatic lipids.
The effects described in the study are only observable if fructose is taken in its liquid form.
With sweetened beverages, fructose is quickly absorbed and it reaches the liver massively, producing the described metabolic alterations. On the other hand, when we eat fruit, the amount of fructose taken is a lot lower compared to a sweetened drink.
“Also, the process of chewing it and the presence of other elements in the fruit, such as fibre, slows down the absorption of fructose and its arrival to the liver”, the researchers said.