HFCS and regular sugar are similar, but there's still a difference in how the body responds.
Tests on animals have shown significant damage from intake of HFCS not present in animals consuming the same amount of regular sugar.
Why? Don't think they know yet.
Regular sugar contains fructose and glucose in the form of sucrose. HFCS contains free fructose and glucose and also contains various traces from the starch -> sugar conversion.
Does the hydrolysis in the body that breaks up sucrose also trigger something else that reduces the effect of fructose in the liver?
Does sucrase regulate hydrolysis of sucrose and thereby reduces the amount of glucose and fructose available to the body compared to HFCS?
Does HFCS somehow disturb sucrase production?
Is is possible that the HFCS still contains enough trace amounts of the amino acids used to break down the starch to create a similar reaction in the food consumed together with the HFCS?
Are the proteins present after the HFCS process harmful?