Function: Humans have a limited ability to metabolize fructose (fruit sugar). Fructose is metabolized differently from other sugars. A fructose load leads to accumulation of fructose-1-phosphate in cells which may partially deplete intracellular ATP levels in susceptible individuals. Decreased cellular ATP causes disturbances in protein, DNA & RNA synthesis, interference with cyclic AMP formation, and reduced ammonia detoxification. Elevations of lactate, uric acid, and triglycerides may result with implications for gout and cardiovascular disease. Several forms of hereditary fructose intolerance have been described. Deficiency Symptoms: Since fructose intolerance is a cellular event, rather than a single nutrient deficiency, symptoms may vary widely among persons. Preliminary evidence suggests clinical symptoms of fructose intolerance may include fatigue, headaches, weakness, dizziness, behavioral changes, and depressed immune function. Medical literature suggests that certain individuals with fructose intolerance may show hypertriglyceridemia, elevation of uric acid, and interference with copper metabolism. Repletion Information: Dietary sources of fructose are numerous; however, an excess intake of fructose should be avoided, rather than absolute removal of dietary fructose. In this manner, whole foods containing fructose (fruits and some vegetables) may be consumed, in order to benefit from their overall nutritional value. Foods very rich in fructose include table sugar (sucrose), high fructose corn syrup, corn syrup, fruit juice concentrates and a large list of prepared foods containing sucrose and/or corn syrup. Reduction of excess dietary fructose intake by avoidance of foods very rich in fructose is suggested when fructose intolerance is exhibited.