More than half of the American diet is comprised of carbohydrates. Are you surprised? From bread, pasta, rice and desserts to healthier fare, such as fruit and yogurt, the American population loves their sugar. Specific types of carbohydrates include monosaccharides, disaccharides, oligosaccharides and polysaccharides. Monosaccharides are the simplest of carbohydrates and they include fructose, glucose and galactose.
When compared to glucose and galactose, fructose is the sweetest monosaccharide. Common names for fructose include "levulose" and "fruit sugar." In food, fructose is typically attached to glucose in a 1:1 ratio, creating a disaccharide called sucrose. Fructose can also be found as a free monosaccharide, however, this is not common.
High Fructose Corn Syrup
High fructose corn syrup is made by chemically changing the glucose in cornstarch to fructose. In addition to being extremely sweet, it is very cheap. As a result, more than half of America's sugar consumption is in the form of high fructose corn syrup. Thus, there remains much speculation that the increase in high fructose corn syrup consumption is correlated with the obesity epidemic. However, this could be the result of an overall increase in the number of calories people eat. More research is needed to further evaluate this hypothesis.
Fructose intolerance is a hereditary disease that results in an error in carbohydrate metabolism. The individual cannot convert fructose to glucose; thereby, fructose cannot be properly digested. This disorder is usually diagnosed once an infant begins consuming fruit. Common symptoms include vomiting, enlarged liver, low blood sugar, failure to thrive, renal tubular defects after fructose consumption and an increase in blood and urine fructose. Once diagnosed, sucrose and fructose are removed from the diet to prevent further complications.
Fructose Food Sources
The majority of fruits are comprised of 1 percent to 7 percent fructose while vegetables are comprised of 3 percent. Honey is comprised of 40 percent fructose. The riper the fruit, the more fructose it contains. This is due to the breakdown of sucrose into glucose and fructose, which makes the fruit taste sweeter. The fruits that contain the highest concentrations of fructose include dried figs, grapes, pears and apples. Sweet onion, sweet corn and sweet red pepper are the vegetables with the highest concentrations.
- Krause's Food & Nutrition Therapy; L. Kathleen Mahan, Sylvia Escott-Stump
- Harvard School of Public Health: High-Fructose Corn Syrup and Health
- Annual Review of Medicine: Role of fructose-containing sugars in the epidemics of obesity and metabolic syndrome
Laura Michele Oliver received her bachelor's degree in nutrition from Auburn University. She served as a dietetic intern at Rush University Medical Center in Chicago, where she also graduated with a Master of Science in clinical nutrition. She now works as a registered dietitian in Brooklyn, N.Y.