D-Fructose Health Effects
- Metabolism: Free fructose is absorbed directly by the intestine. When fructose is consumed in the form of sucrose, it is digested (broken down) and then absorbed as free fructose. Fructose absorption occurs on the mucosal membrane via facilitated transport involving GLUT5 and GLUT2 transport proteins. Fructose is phosphorylated in the liver by fructokinase (Km= 0.5 mM). Fructokinase initially produces fructose 1-phosphate, which is split by aldolase B to produce the trioses dihydroxyacetone phosphate (DHAP) and glyceraldehyde. DHAP is then converted to glycerol-3-phophate which stimulates production of triglycerides. Nearly half (45%) of all pure fructose consumed is used up within 3-6 hours by the body for energy. If fructose is consumed with glucose (as it typically is in nature), up to 66% of it is used for energy within the same time frame. Roughly a third (29%) to a half (54%) of all fructose consumed is converted to glucose. Less than 1% of fructose appears to be directly converted to triglycerides.
- Health Effects: Acute consumption of fructose or high fructose corn syrup is essentially non-toxic. Chronic, excess fructose consumption has been shown to be a cause (or indirect cause) of gout, insulin resistance, hypertension, obesity, fatty liver disease, elevated LDL cholesterol and elevated triglycerides, leading to metabolic syndrome. In Wistar rats, a laboratory model of diabetes, 10% fructose feeding as opposed to 10% glucose feeding was found to increase blood triglyceride levels by 86%, whereas the same amount of glucose had no effect on triglycerides. A 2008 study found a substantial risk of incident gout associated with the consumption of fructose or fructose-rich foods. It is suspected that the fructose found in soft drinks (e.g., carbonated beverages) and other sweetened drinks is the primary reason for this increased incidence.
- Route of Exposure: Ingestion
- Carcinogenicity: No indication of carcinogenicity to humans (not listed by IARC).
- Toxicity: Consuming more than 100 g a day of pure fructose may lead to a modest but statistically significant rise in body weight of 0.44 kg a week. Consuming 100 g or more of fructose a day also significantly increases fasting levels of serum triglycerides. LD50: 15000 mg/kg (intravenous, rabbit)
Mechanism of Action
|Target Name||Mechanism of Action||References|
Superoxide dismutase [Cu-Zn]
Solute carrier family 2, facilitated glucose transporter member 2
Solute carrier family 2, facilitated glucose transporter member 5