I've been poking about the literature lately ever since the insulinogenic (in terms of circulating insulin levels but not necessarily secretion of insulin) properties of jelly beans were made known to me a while back. I've been looking into studies comparing sucrose to glucose or fructose separately, or that measure insulin secretion and/or clearance per se. It's a rough go. Much of the research that turns up with fructose in the search phrase involves HFCS not fructose per se. When you get isolated fructose studied, however, there are still other complications.
For starters, it is impossible to isolate the effect of just fructose with whole foods. Just about every source of fructose, like fruits, also contains sucrose and even considerable amounts of isolated glucose in many cases. It is also virtually impossible to attain the levels of fructose generally required to elicit a measurable metabolic response. For reference, a medium apple contains roughly 10g fructose (most of which is free). A "bolus dose" for 50g would be difficult to achieve and would come with ~5g glucose per apple. So ... sweetened beverages it is as the major dietary vehicle by which fructose is incorporated into dietary interventions.
