And yet, the research. Maybe high-fructose corn syrup has more differences than just the fructose/glucose levels?
Yes, let's talk about "the research." I've been following this fairly closely for a decade.
About a decade ago I got into an argument with a friend over the overconsumption of sugar. I, like you, assumed with all the bad press about HCFS (even back then) that it was terrible for you. So, I started looking for reliable, clear studies that proved it.
The problem was: THERE WEREN'T ANY. Since then, there have been a few, but given how many people are shouting about how terrible HFCS is, it seems surprisingly hard to prove it.
Let me summarize the state of current research:
(1) Pure fructose vs. glucose -- there are dozens of studies showing that pure fructose screws up metabolism in rats and humans much worse than glucose.
(2) Pure fructose vs. sucrose -- there are dozens of studies showing that pure fructose screws up metabolism in rates and human much worse than sucrose.
(3) HFCS (~50/50 mixture of fructose and glucose) vs. sucrose -- until about 2010 and that Princeton study, there were basically NO STUDIES that showed a statistically significant difference between consumption of HFCS vs. sucrose (table sugar). To the contrary, there are at least a dozen or so studies out there if you look where they tried looking for a difference and didn't really find one.
This surprised me, given what I had been told about HFCS, but it also makes sense given that HFCS is basically about 50/50 fructose/glucose, which is very close to what sucrose becomes very early in the digestive process.
The vast majority of people who are shouting "HFCS is terrible!" tend to cite the studies in categories (1) and (2). You did precisely that in your quote from the Journal of Clinical Investigation. A number of studies in the past which tried measuring pure fructose and found significant differences found that there were little to no measurable differences when they substituted HFCS for the fructose.
I'm very interested in the studies in category (3). They include your Princeton citation, as well as a more recent study out of the University of Utah. There was also a bit of attention given to recent population-based study which claimed to find a correlation between diabetes and HFCS availability in different countries. (These sorts of population studies are always notoriously difficult to do well statistically, since there are always a ridiculous number of confounding factors, but I mention it because it's one of the few such things out there.)
The problem is that these HFCS studies are fighting an uphill battle -- as I said, prior to 2010 there were studies that measured HFCS vs. sucrose and tended to find no significant differences. Which also leads to the question now about whether the Princeton and Utah studies could be an example of publication bias -- we only tend to see them because those studies show an effect which hadn't been observed previously, but perhaps those effects are due to random chance or unintentional changes in study design. (And since HFCS had been branded as bad long before any rigorous scientific evidence was available, there are probably a lot of groups looking for effects... and yet we only have 2-3 studies.)
Despite what the powerful corn lobby in the US would have you believe, corn is just not all that good for you in large amounts. And with the amount that goes into HFCS, drinking soda pop is getting corn in large amounts.
To be clear: I think HFCS is terrible, and the whole corn growers industry needs to be rethought, since our agricultural subsidies for corn are distorting the economy and our food production network. But the problem with HFCS is that (1) it's cheap due to the subsidies, and (2) it's liquid, so it can be blended easily, leading to companies throwing it randomly into all sorts of foods where it really isn't needed.
I think the concern about metabolic differences is much lower on the list of things to be worried about, at least until we get a stronger scientific consensus about how bad HFCS might be compared to sucrose. (Another notable thing: honey is often touted as a better substitute by "natural foods" people, but it basically has a composition very similar to HFCS with a few trace nutrients. I'd think a comparative study with honey vs. sucrose vs. HFCS might also be informative....)
I thoroughly agree with you that we should stop subsidizing HFCS production. But as to the question of whether drinking a soda with 10 teaspoons of sucrose is "better for you" than drinking a soda with 10 teaspoons of HFCS -- I think the scientific "jury is still out."
But I also think the scientific "jury" can tell you one thing clearly: Americans eat too much sugar in general. Switching all that sugar from HFCS to sucrose may be slightly better, but it's NOT going to solve our obesity problem.