Editing Fructose (section)

=== Capacity and rate of absorption ===
The absorption capacity for fructose in monosaccharide form ranges from less than 5&nbsp;g to 50&nbsp;g (per individual serving) and adapts with changes in dietary fructose intake.<ref name=fuji /> Studies show the greatest absorption rate occurs when glucose and fructose are administered in equal quantities.<ref name=fuji>{{cite journal | last=Fujisawa | first=T |author2=Riby J |author3=Kretchmer N  | title=Intestinal absorption of fructose in the rat | year=1991 | journal=Gastroenterology | volume=101 | pages=360–367 | pmid=2065911 | issue=2| doi=10.1016/0016-5085(91)90012-a }}</ref> When fructose is ingested as part of the disaccharide sucrose, absorption capacity is much higher because fructose exists in a 1:1 ratio with glucose. It appears that the [[GLUT5]] transfer rate may be saturated at low levels, and absorption is increased through joint absorption with glucose.<ref>{{cite journal | last=Ushijima | first=K |author2=Fujisawa T |author3=Riby J |author4=Kretchmer N  | title= Absorption of fructose by isolated small intestine of rats is via a specific saturable carrier in the absence of glucose and by the disaccharidase-related transport system in the presence of glucose | year=1991 | journal= Journal of Nutrition | volume=125 | pages=2156–2164 | pmid=7643250 | issue=8| doi=10.1093/jn/125.8.2156 }}</ref> One proposed mechanism for this phenomenon is a glucose-dependent [[cotransport]] of fructose.
In addition, fructose transfer activity increases with dietary fructose intake. The presence of fructose in the lumen causes increased mRNA transcription of GLUT5, leading to increased transport proteins. High-fructose diets (>2.4 g/kg body wt) increase the transport proteins within three days of intake.<ref>{{cite journal | last=Ferraris | first=R | title= Dietary and developmental regulation of intestinal sugar transport | year=2001 | journal= Biochemical Journal| volume=360 | pages=265–276 | pmid=11716754 | doi= 10.1042/0264-6021:3600265 | issue=Pt 2 | pmc=1222226}}</ref>