It doesn't even mean glucose. Glucose is, as best we can tell, just fine. Which is almost a given, considering "blood sugar"- a key way your body distributes energy to your cells- is glucose.
Most studies that conclude "sugar" is "toxic" are talking about fructose, which is metabolized differently than glucose. This means fructose (e.g. HFCS) and sucrose (table sugar, e.g. cane sugar)
Obviously glucose is fine at some level -- as you say, the body uses it internally.
But that doesn't mean that there wouldn't still be a problem if we only got rid of the fructose we're eating and replaced it with glucose. The quantity of glucose we would then be ingesting with each meal would be quite large, and that might have other negative consequences -- mediated, perhaps, by the even larger insulin release that would be triggered.
But I'm only speculating. I haven't come across any research that bears on this question. If you have, I'd like to see it.
You are correct. HFCS is unassociated glucose and fructose, and to my understanding is pretty much interchangeable with sucrose, as sucrose is enzymatically cloven almost immediately.
I will throw in that firstly, it is theorized that the fiber in apples etc provides some regulation to the absorption of the fructose and that somehow changes matters. Secondly, and in my mind more importantly, it is much easier to gorge on pure sugar than it is to eat an equivalent amount of sugar in the form of apples.
I'd also point out that there's no way in hell we evolved a metabolism that expected ready access to as much fruit as we could eat for 12 months of the year.
Why is that? In nature, different fruits ripen at different times. Even if you were restricted to nature's cycle, there could potentially be fruit available for most of the year.
I mean, sure, you wouldn't have access to all of these fruits in one location, but point being fruit wasn't something you got for a week in June, then never again until next June.
Most studies that conclude "sugar" is "toxic" are talking about fructose, which is metabolized differently than glucose. This means fructose (e.g. HFCS) and sucrose (table sugar, e.g. cane sugar)