Fructose is commonly known as fruit sugar. It makes fruits sweet, but it is also a component of ordinary table sugar as well as honey. There are literally thousands of types of sugars that all share a common structure. Fructose and glucose are the most common simple sugars. They are called monosaccharide because they consist of a single, unique molecular structure.

Common table sugar is a disaccharide that consists of a molecule of glucose and a molecule of fructose chemically bonded so that it is 50 percent glucose and 50 percent fructose.

The body’s metabolism cannot use the disaccharide directly. To be useful, enzymes must first break the bond between the two monosaccharides making the glucose and fructose available to be used.

High-fructose corn syrup is not really high in fructose at all, but it is higher than corn syrup, which is nearly pure glucose. The composition of high-fructose corn syrup is either 42 percent or 55 percent fructose, which is comparable to sucrose with 50 percent fructose.

It is true that the pancreas is insulin-resistant to all types of fructose, but the studies that have been done on the effects of fructose have been done using pure fructose, not fructose-glucose combinations. Using fructose independently makes these studies not representative of normal diets and cannot be applied to high-fructose corn syrup that contains both sucrose and glucose.

Critics of the extensive use of high-fructose corn syrup in food sweetening argue that the highly processed sugar is more harmful to humans than regular sugar, contributing to weight gain by affecting normal appetite functions. This has been shown not to be the case except in the case of pure fructose in unrealistically high doses.

Studies by the American Medical Association suggest that it appears unlikely that high-fructose corn syrup contributes more to obesity or other conditions than sucrose. Other research has disputed the links between high-fructose corn syrup and obesity, diabetes and metabolic syndrome.

According to U.S. Department of Agriculture data, the consumption of high-fructose corn syrup has been declining since 2000 as sucrose usage has increased and obesity and diabetes rates continue to rise. The Mayo Clinic, an institution at the forefront of medical and dietary research, reports that there is insufficient evidence to say that high-fructose corn syrup is less healthful than other types of added sweeteners.

Reports of fears that genetically modified corn has been used to produce high-fructose corn syrup are unfounded. Although genetically modified corn has been used to produce the high-fructose syrup, existing research indicates that corn DNA, genetically modified or otherwise, cannot be detected in the product.

There may be reasons to resist genetically modified corn, but high-fructose corn syrup is not one of them.

Although some research results suggest a higher weight gain in rats that consumed high-fructose corn syrup compared with sucrose, there have been too few long-term studies to draw firm conclusions. The only feasible difference between sucrose and high-fructose corn syrup is that for high-fructose corn syrup, no enzymatic action is required to break apart the disaccharide molecule before the sugars are metabolically active.

The effects of this missing step in the metabolic pathway have yet to be studied, and to date there are no data to validate this as a probable cause of any health issues.

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Richard Brill is a professor of science at Honolulu Community College. Email questions and comments to brill@hawaii.edu.