Fructose is the form of sugar found in most fruit (particularly apples and pears), but also in vegetables such as onions, radishes, artichokes, asparagus and leeks. Other foods that are high in this form of sugar include honey, corn syrup and wheat. It is used to replace lactose in some lactose free dairy products. It can be used as a very safe treatment for nausea and morning sickness of pregnancy, and works within a fructose must be avoided by diabetics.
The malabsorption of fructose may be a cause of irritable bowel syndrome. This can be tested for by specific pathology tests and by an exclusion diet. The fructose level in seminal fluid (the fluid ejaculated by a man during sex) is sometimes measured as an investigation of male infertility. Fructose is the energy source for sperm and low levels cause reduced sperm movement.