If you have been following the recent media coverage of fructose and high-fructose corn syrup, chances are good that you are confused by the often contradictory reports about these sweeteners. On the one hand, studies warning of their negative effects on health seem to be flooding magazines, television, and newspapers. On the other hand, reports attesting to the safety of these popular sweeteners are also common. What is the truth about fructose and high-fructose corn syrup? Are they safe, or are they potentially harmful to our health?
To add to the confusion, high-fructose corn syrup is not really high in fructose at all compared with other common sweeteners. In fact, it has about the same proportions of fructose and glucose as table sugar (sucrose). Many other sweeteners — including honey, maple syrup, and molasses — contain both fructose and glucose in varying proportions.
To understand the debate surrounding fructose and high-fructose corn syrup, it’s important to understand what they are, where they are found, and how our bodies break them down.
What is fructose?
Fructose is a monosaccharide, or simple sugar, which means that its basic structure consists of six carbon atoms joined in a ring. Like other dietary sugars, fructose provides about 15 calories per teaspoon and is digested in and absorbed from the small intestine. However, there are important differences in the way fructose is handled by the body compared with other sugars.
The two main dietary sources of fructose are fruits, where it is found in high concentrations (hence its common name, “fruit sugar”); and sucrose, or table sugar, which is formed by the combination of equal amounts of fructose and glucose. Fructose is also found in honey, maple syrup, agave syrup, brown rice syrup, and in small amounts in a scattering of vegetables.
In addition, fructose is present in the commercially prepared liquid sweetener known as high-fructose corn syrup, or HFCS. High-fructose corn syrup is formed by a complex process in which corn is first processed into cornstarch, which is then treated with enzymes to form corn syrup. “High-fructose” is used in the title to differentiate the product from regular corn syrup, which is mostly glucose. Because it is inexpensive, mixes well with other ingredients, and helps keep foods moist, high-fructose corn syrup is widely used by the food industry as an alternative to sucrose in many processed and prepared foods and beverages. There are two common types of high-fructose corn syrup now used in the United States: HFCS 55, which is 55% fructose and 42% glucose and is used mostly in soft drinks, fruit juice blends, and other beverages; and HFCS 42, which is 42% fructose and 53% glucose and is used in yogurt, baked goods, frozen desserts, breakfast cereals, and other prepared foods.
Glucose, another simple sugar, is the body’s main fuel source and is readily burned for energy. This is because glucose is carried into cells throughout the body by the hormone insulin, which also regulates the level of glucose in the blood. Fructose, on the other hand, is not easily used by the body for fuel. It is not transported into cells by insulin; instead, fructose is taken from the small intestine to the liver by a special carrier protein known as GLUT-2. Once inside the liver, fructose undergoes a number of complex biochemical reactions that can lead to the formation of a number of different compounds, including glycogen (a stored form of glucose), triglycerides (a type of fat found in the blood, often linked to weight gain and obesity), and some types of fatty acids. Fructose may also be converted to the chemical uric acid, which in high levels may stress the kidneys and other organs, thereby increasing the risk of developing gout, kidney stones, and other chronic conditions. This fundamental difference in the way fructose is handled by the body, compared with glucose, has made it the target of studies exploring its possible ill effects on health.