“Walk through any supermarket and take a look at the labels on food products, and you’ll see that many of them contain fructose, often in the form of sucrose (table sugar),” says professor Wilhelm Krek ofETH Zurich’s Institute for Molecular Health Sciences.
Fructose, as an artificial additive, is contained in prepared foods and soft drinks, as well as alledgedly healthy fruit juices, frequently in high quantities.
In the past few decades fructose spread all through the food market, because of a perception as being less harmful than glucose. Compared to glucose, fructose scarcely increases blood glucose levels and insulin secretion. This circumvents recurrent insulin spikes after any glucose consumption, which are deemed harmful.
Not only that, but fructose tastes sweeter.
But there is a downside.
Your liver converts fructose very efficiently into fat. Individuals who consume too much high-fructose food can, over time, become overweight and develop high blood pressure, dyslipidaemia with fatty liver, and insulin resistance — symptoms that doctors group together under the name metabolic syndrome.
But Krek and team member Peter Mirtschink have discovered a more troubling side effect of fructose.
They uncovered a heretofore unknown molecular reaction that points to fructose as a major driver of uncontrolled growth of the heart muscle, a condition that can lead to fatal heart failure.
In a person with high blood pressure, the heart has to grow, since it takes more strength to pump the blood through the circulatory system. These growing heart muscle cells require an ample amount of oxygen.
But because insufficient oxygen is available to satisfactorily supply the increased growth, the cells switch to an alternate energy supply.
Instead of drawing energy from fatty acids, they rely more on an anaerobic process called glycolysis. The word means, literally, the “splitting of sugars.” If the heart muscle cells can access fructose in addition to glucose, this can set off a fatal chain reaction.
Fruit Is Good
Large volumes of fructose are added to many foods, but principally to sweet beverages and soft drinks. This has skyrocketed per capita consumption of high fructose corn syrup in the United States between 1970 and 1997, from 230 grams (about half a pound) per year to over 28 kilograms (nearly 62 pounds).
But Mirtschink gives reassurance that eating a normal amount of fruit daily is safe and healthy. “Besides fructose, fruit contains plenty of important trace elements, vitamins, and fiber,” he says.
People should, however, avoid overly sweet soft drinks and fruit juices—these often have sugar added—as well as ready-made meals and other foods to which large amounts of fructose are added as a flavor carrier.
“Just this surplus of fructose can help trigger the mechanism we have described if one of the stress factors is present, such as cardiac valve disease or high blood pressure,” Mirtschink emphasizes.
Peter Mirtschink, Jaya Krishnan, Fiona Grimm, Alexandre Sarre, Manuel Hörl, Melis Kayikci, Niklaus Fankhauser, Yann Christinat, Cédric Cortijo, Owen Feehan, Ana Vukolic, Samuel Sossalla, Sebastian N. Stehr, Jernej Ule, Nicola Zamboni, Thierry Pedrazzini & Wilhelm Krek HIF-driven SF3B1 induces KHK-C to enforce fructolysis and heart disease Nature (2015) doi:10.1038/nature14508