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Studies on the glycemic index of raisins and on the intestinal absorption of fructose

by 1973- Kim, Yeonsoo

Abstract (Summary)
The glycemic index (GI) measures the magnitude of the postprandial increase in blood glucose caused by a test food compared with a reference food/beverage, such as a glucose solution or white bread, containing the same amount of carbohydrate. The insulin index is determined in a similar manner of GI calculation, except that blood insulin AUC is used in place of blood glucose AUC. Low GI and insulin index foods are desirable because foods with low GI and insulin index result in gradual increase in postprandial glycemia/insulinemia and lower blood glucose/insulin fluctuations compared with foods with high GI and insulin index. This attenuated glycemic and insulinemic responses of low GI and insulin index foods is associated with reduced risks of obesity, diabetes mellitus, and chronic diseases. Fructose has low glycemic and insulin index, and a high fructose-containing food, such as raisins, would be expected to have low glycemic and insulin index values. In addition to its low glycemic and insulin index, small, or “catalytic” amounts of fructose (e.g., 5- 10 g) lower the glycemic response to other carbohydrates. However, prefeeding of fructose is necessary to achieve this effect due to the slow intestinal absorption of fructose. The overall objective of this dissertation was to investigate the current interest of carbohydrate metabolism. The first goal was to determine a difference in carbohydrate iii metabolism in populations with different metabolic status. The second objective was to determine fructose absorption in the presence of erythritol in vivo and in vitro. The GI and insulin index of raisins were determined and compared in healthy sedentary young adults, endurance athletes, and people with impaired glucose tolerance. The GI of raisins was low (GI ?55) in the healthy sedentary people (49.4 ± 7.4) and people with pre-diabetes (49.6 ± 4.8) and was moderate (GI 55-69) in the athletes (62.3 ± 10.5), but there were no differences among the subject groups (P = 0.437). The insulin index of raisins was not significantly different among the groups. Raisins are a low to moderate GI food, with a correspondingly low insulin index. In the second study, the effect of the simultaneous ingestion of an equimolar amount of erythritol and fructose on fructose absorption was determined in healthy subjects. Breath hydrogen production with a beverage of equimolar mixture of 50 g fructose and 33.3 g erythritol (FE) was 207% higher than that of a beverage of 50 g fructose (F) (P <0.05). Serum fructose levels were 20% lower in the FE compared with F (P < 0.05). However, serum erythritol level in FE was increased to 727.7 ± 22.2 mmol/min/L, which it was negligible in F (P < 0.05). The rise in breath hydrogen levels in FE versus F indicated greater carbohydrate malabsorption. Because of the considerable rise in serum erythritol and the decrease in serum fructose in the FE versus F groups, it appeared that erythritol was absorbed at the expense of fructose. The third study investigated the effect of erythritol on intestinal fructose absorption using Caco-2 cells. The inhibitory effect of erythritol on fructose absorption that we observed in healthy humans was reproducible in a Caco-2 cell model at high iii doses of fructose and erythritol. Erythritol inhibited fructose absorption in a dosedependent fashion (P < 0.05). In conclusion, raisins, a high fructose-containing food, has a low GI and insulin index. A mixture of an equimolar amount of fructose and erythritol also had low glycemic and insulinemic responses. However, increased gastrointestinal distress after intake of the mixture of fructose and erythritol may limit the usage of those carbohydrates. Further research should focus on the interaction of sugar alcohol s and other food components which may impact on carbohydrate absorption and gastrointestinal distress. iv
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School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:fructose in human nutrition carbohydrates raisins glycemic index

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