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Heart health fructose dangerous for the heart
Fructose has long been considered harmless to health, but in recent years increasingly critical aspects of excessive intake of fructose have come to the fore. Researchers at the Swiss Federal Institute of Technology Zurich (ETHZ) have now discovered a new fructose-dependent molecular mechanism that can contribute to the enlargement of the heart muscle and, in the worst case, heart failure. Their results were published in the renowned journal "Nature".
Fructose has been used more extensively by the food industry in recent decades, as fructose was considered less harmful to glucose, according to the Communication from ETH Zurich. In contrast to glucose, fructose hardly causes any insulin secretion and blood glucose levels rise only slightly. Recurring insulin spikes, which follow with each intake of glucose-containing food and are critically evaluated healthily, could be avoided by the fructose. In addition, people would perceive the fructose as much sweeter in the taste. However, fructose may also have negative health effects, as evidenced by the current study by Professor Wilhelm Krek and Peter Mirtschink.
In particular, lemonade and sweetened fruit juices warn the researchers due to the high fructose content. (Image: Brent Hofacker / fotolia.com) Fructose is found in many foods
Fructose is now used in many foods for sweetening, although consumers are often unaware of this. "Once you go through a supermarket and look at the labels of food - in many of them, fructose is also contained in the form of sucrose, ie table sugar," reports Professor Wilhelm Krek from the Institute of Molecular Health Sciences at ETH Zurich. Above all finished products, lemonades but also the allegedly healthy fruit juices would often contain large amounts of artificially added fructose. According to the researchers, this is questionable for health. Because fructose have the disadvantage that they are very efficiently converted into fat by the liver and therefore threatened with excessive intake over time, the development of obesity, high blood pressure, lipid metabolism disorders with fatty liver and insulin resistance. In summary, this medical condition is called the medical term metabolic syndrome.
Uncontrolled growth of the heart muscle
In addition, the Swiss researchers have now been able to prove another explosive effect of fructose. They discovered a hitherto unknown molecular mechanism that identifies fructose as a major driver of uncontrolled growth of the heart muscle in hypertensive patients, leading to fatal heart failure, according to the ETH Zurich Communication. The heart of people with hypertension needs to grow in order to pump the blood more into the circulation, but the growing heart muscle cells need a lot of oxygen. Because not enough oxygen can be provided during the increased growth, the cells convert their energy production and instead of gaining energy from fatty acids, so-called glycolysis, ie the oxygen-free splitting of sugars, increasingly used, the researchers report. If the cardiomyocytes can also resort to fructose in addition to glucose, a fatal chain reaction will result.
Fructose set the vicious circle in motion
In the case of the discovered chain reaction, the lack of oxygen in the cardiac cells causes the release of the molecule HIF, which acts as a "universal molecular switch, always in pathological growth processes, be it in cardiac enlargement or cancer," according to the Communication from ETH Zurich. In the heart muscle cells, the HIF molecule stimulates the production of the enzyme ketohexokinase-C (KHK-C), which plays a central role in fructose metabolism, has a high affinity for fructose and can process the latter very efficiently. Glycolysis is also enhanced by the formation of KHK-C. "Since the metabolism of fructose knows no negative feedback, a vicious circle begins, which can lead to heart failure," reports ETH Zurich. The scientists have demonstrated this mechanism not only on mouse models, but also on biological samples from patients suffering from morbid cardiac enlargement with a corresponding narrowing of the heart valve to the main artery. Cardiac muscle cell specimens were obtained from cardiac surgery, and in fact, ETH Zurich researchers detected more HIF and KHK-C molecules. In mice that suffered from chronic hypertension, the scientists were also able to prevent the enlargement of the heart by eliminating the KHK enzyme.
Avoid sugared sodas and fruit juices
In their latest study, the researchers rate the addition of fructose in foods, sweeteners and sodas to be extremely critical. In the United States, consumption of high-fructose corn syrup increased from 230 grams a year per capita to over 28 kilograms between 1970 and 1997. The normal fructose in fruit, according to the experts, but harmless. An ordinary daily fruit is healthy and uncritical, reports Peter Mirtschink. "In addition to fructose, fruits also contain numerous important trace elements, vitamins and fiber," continues the Swiss researcher. To avoid, however, are highly sugared sodas and fruit juices, ready meals and other foods in which large amounts of fructose are used as a flavor carrier. Because they could "help to get the mechanism we have described in motion when one of the stress factors, such as valvular heart disease or hypertension, is present," explains Mirtschink. (Fp)