Both sucrose and high fructose corn syrup are types of sugars, which are simple forms of carbohydrates, used to add extra sweetness to foods. They are highly refined and processed, stripped of many corresponding nutrients that would constitute a healthy diet. Because refined sugars are absorbed and metabolized so quickly by the body, they have been cited as potential causes of obesity.
Carbohydrates are made up of simple sugar units called monosaccharides. Each unit has a specific chemical formula: one carbon atom to two hydrogen atoms to one oxygen atom. Glucose and fructose are two monosaccharide units. They are isomers of each other, meaning that they have the same chemical formula but differ in their structure. When monosaccharides are linked together, they form more complex carbohydrate molecules.
One type of carbohydrate is sucrose, also known as table sugar. It's a disaccharide, meaning that it is composed of a glucose unit and fructose unit bonded together. Both units appear in equal proportion. High fructose corn syrup, on the other hand, is a liquid sweetener. It features an imbalanced ratio, containing 55 percent fructose and 42 percent glucose. Larger sugar molecules constitute the remaining 3 percent.
Sucrose is a carbohydrate that occurs naturally in many fruits. It is also synthesized and processed as table sugar. But high fructose corn sugar does not occur naturally. It was invented in 1957 by Richard O. Marshall and Earl M. Kooi to tailor the specific level of sweetness. The sugar is made when corn syrup is heated and then separated to break the gluten bonds and release the starch and fiber. Then enzymes are used to reconfigure the structure of the sugars. Though the process is complicated, high fructose corn syrup is actually cheaper to manufacture.
The American Medical Association suggests that because of the similarities in composition, "it appears unlikely that HFCS contributes more to obesity or other conditions than sucrose." In fact, a 2007 study in the journal "Nutrition" found that sucrose and high fructose corn syrup have very similar effects on the hormones leptin and ghrelin — hunger controlling hormones — in normal-weight women. But in 2010, a research team from Princeton University published a paper in the journal "Pharmacology, Biochemistry and Behavior" that demonstrated rats with access to high fructose corn syrup gained significantly more weight than rats that consumed sucrose, despite equivalent calorie intake. More research still needs to be done to ascertain their differences.
Whereas glucose can be metabolized by every cell of the body, fructose can only be metabolized by the liver, which is similar to the way in which alcohol is metabolized. High fructose corn syrup, therefore, will be metabolized slightly more by the liver. Fructose actually has the lowest insulin response amongst all natural sugars, but it has still been known to cause obesity and liver disease.