Fructose is suspected of driving the development of metabolic syndrome and fatty liver. A study by Swiss scientists has now shown what regular consumption of fructose-containing soft drinks can do to healthy, slim young men after only a few weeks.
The incidence of non-alcoholic fatty liver disease (NAFLD) increases significantly - similar to the incidence of type 2 diabetes and metabolic syndrome. Increased sugar consumption is associated with it, and this is especially true for the consumption of fructose. Unlike glucose, which can be used directly by most body cells to produce energy, fructose must first be metabolised in the liver. In the process, more triglycerides are produced, which are then deposited in the liver or fatty tissue in the form of fat.
Fructose consumption - especially in the form of sweetened soft drinks - has increased greatly in recent decades. It should be borne in mind that even the usual household sugar (sucrose) consists of half fructose. Until now, it was unclear how long it takes and how much fructose is needed to have a negative effect on the metabolism and the liver.
In order to clarify this question, the research group led by Bettina Geidl-Flueck from the University Hospital Zurich conducted a randomised study with 94 young healthy men (18 to 30 years). The slim test persons were divided into four groups by lottery: Three groups were to consume three glasses (à 0.2 l) of a provided sweet drink daily, the fourth group was instructed to completely abstain from sweet drinks during the 7-week study period. In group 1, the drinks contained fructose, in group 2 glucose and in group 3 sucrose, each in a dose of 13.3 g/dl. To follow the path of the different sugars in the body, they were marked with tracers.
A significant influence on body weight was not observed by the sweet drinks within the seven weeks, only in the glucose group there was a slight increase of 0.8 kg on average. Apparently, the young men saved the additional calories elsewhere.
There were clear differences in fat metabolism: in the fructose group, the body's own fat production in the liver was twice as high as in the glucose group or in the control group (fractional secretion rates or FSR 19.7% vs. 9.1% per day). The effect was still detectable more than 12 hours after the last sweet drink or meal. This proves that fructose is obviously converted into fatty acids in larger quantities, the authors write.
In the sucrose group, fat production in the liver was even higher (FSR 20.8%), although the fructose content in household sugar is only 50%. The authors explain this by the fact that the glucose also contained in household sugar increases the absorption of fructose in the intestine. In addition, the glucose-induced insulin release activates enzymes for fat formation.
The increased production of fat in the liver is considered the first decisive step in the development of diseases such as fatty liver or type 2 diabetes. The authors indicated that restrictions on the consumption of sweetened beverages and food could thus be an important preventive measure.
Source:
Geidl-Flueck B, Hochuli M, Németh Á, Eberl A, Derron N, Köfeler HC, Tappy L, Berneis K, Spinas GA, Gerber PA. Fructose- and sucrose- but not glucose-sweetened beverages promote hepatic de novo lipogenesis: A randomized controlled trial. J Hepatol. 2021 Mar 6:S0168-8278(21)00161-6. doi: 10.1016/j.jhep.2021.02.027. Epub ahead of print. PMID: 33684506.