Agave syrup has a lower glycemic index (than sucrose), and it’s marketed as a “health food” for this reason. But this is because it’s mostly fructose, which has to be metabolized in the liver. So it doesn’t cause the (maybe dangerous) blood sugar spikes, which means you also miss out on the satiety that would normally cause, and may thus overeat and get non-alcoholic fatty liver disease instead. Fructose is more intensely sweet than sucrose, so there is some additional concern that you could develop tolerance to the sweeter taste when it doesn’t cause satiety and thus train yourself overeat food containing sucrose as well. If all these reasons are true, then agave is very bad for you, and possibly worse than glucose syrup or sucrose (which is a disaccharide molecule made of fructose bonded to glucose).
HFCS is not the same thing as corn syrup. Cornstarch is made into corn syrup by breaking down the starches into their component glucose molecules (originally using heat, pressure, and acid, but it’s now mostly done with enzymes), thus corn syrup is mostly glucose and water. It’s also the primary ingredient in Karo-brand syrup. Corn syrup is made into HFCS (high-fructose corn syrup) by enzymatically converting some portion of the glucose into fructose (commonly about half, to make it a substitute for sucrose), which gives it very different metabolic properties compared to the corn syrup it started from.
I expect agave to be generally preferred over table sugar and HFCS due to having a significantly lower glycemic index. I’m unfamiliar with Karo.
Agave syrup has a lower glycemic index (than sucrose), and it’s marketed as a “health food” for this reason. But this is because it’s mostly fructose, which has to be metabolized in the liver. So it doesn’t cause the (maybe dangerous) blood sugar spikes, which means you also miss out on the satiety that would normally cause, and may thus overeat and get non-alcoholic fatty liver disease instead. Fructose is more intensely sweet than sucrose, so there is some additional concern that you could develop tolerance to the sweeter taste when it doesn’t cause satiety and thus train yourself overeat food containing sucrose as well. If all these reasons are true, then agave is very bad for you, and possibly worse than glucose syrup or sucrose (which is a disaccharide molecule made of fructose bonded to glucose).
HFCS is not the same thing as corn syrup. Cornstarch is made into corn syrup by breaking down the starches into their component glucose molecules (originally using heat, pressure, and acid, but it’s now mostly done with enzymes), thus corn syrup is mostly glucose and water. It’s also the primary ingredient in Karo-brand syrup. Corn syrup is made into HFCS (high-fructose corn syrup) by enzymatically converting some portion of the glucose into fructose (commonly about half, to make it a substitute for sucrose), which gives it very different metabolic properties compared to the corn syrup it started from.