Fructose is a simple sugar (also known as a monosaccharide) that is found in many foods.
Fructose is one of the three most important blood sugars that humans consume, along with glucose and galactose.
Fructose can be found in a variety of naturally sweet foods, including fruits, honey and some root vegetables. These foodstuffs also typically contain sucrose and glucose. Fructose is also a result of the digestion of sucrose. Sucrose is a disaccharide (or complex sugar) that contains both glucose and fructose.
Fructose is recommended as an additive for people with hypoglycemia or diabetes mellitus. This is because its Glycemic Index (or GI) is very low when compared to sucrose (also called cane sugar).
Some people are concerned, however, that it may have a negative effect on plasma lipids.
Fructose depends on glucose to carry it in the blood stream, so its absorption levels without glucose present are very low. Excess fructose is carried to the lower intestine to provide nutrients for flora, which produces gas. It is also known to cause intestinal water retention. This may result in bloating, excessive gas, loose stools or diarrhea; all of these effects are dependent on the amount that has been consumed as well as a variety of other factors.
Some people have hypothesized that fructose causes obesity by elevating triglycerides and LDL cholesterol, which leads to metabolic syndrome. In research, however, adding fructose to the diet of humans has not led to obesity.
Fructose, and all monosaccharides, is a reducing sugar. It is, however, considered 10 times more active when it comes to the formation of glycations than glucose. For this reason, one should limit consumption to avoid damage to cellular and molecular function.