Acute fructose administration decreases the glycemic response to an oral glucose tolerance test in normal adults

In animal models, a small (catalytic) dose of fructose administered with gl ucose decreases the glycemic response to the glucose load. Therefore, we ex amined the effect of fructose on glucose tolerance in 11 healthy human volu nteers (5 men and 6 women). Each subject underwent an oral glucose toleranc e test (OGTT) on 2 separate occasions, at least 1 week apart. Each OGTT con sisted of 75 g glucose with or without 7.5 g fructose (OGTT+F or OGTT-F), i n random order. Arterialized blood samples were obtained from a heated dors al hand vein twice before ingestion of the carbohydrate and every 15 min fo r 2 h afterward. The area under the curve (AUC) of the change in plasma glu cose was 19% less in OGTT+F vs. OGTT-F (P < 0.05). Glucose tolerance was im proved by fructose in 9 subjects and worsened in 2. All 6 subjects with the largest glucose AUC during OGTT-F had a decreased response during OGTT+F ( 31 +/- 5% decrease). The insulin AUC did not differ between the 2 studies. Of the 9 subjects with improved glucose tolerance during the OGTT+F, 5 had smaller insulin AUC during the OGTT+F than the OGTT-F. Plasma glucagon conc entrations declined similarly during OGTT-F and OGTT+F. The blood lactate r esponse was about 50% greater during the OGTT+F (P < 0.05). Neither noneste rified fatty acid nor triglyceride concentrations differed between the two OGTT. In conclusion, low dose fructose improves the glycemic response to an oral glucose load in normal adults without significantly enhancing the ins ulin or triglyceride response. Fructose appears most effective in those nor mal individuals who have the poorest glucose tolerance.