HFCS and sucrose are built from the same sugars - fructose and glucose - in nearly equivalent amounts but in a slightly different way.  The sugars are monosaccharides (free or unbonded) in HFCS; in sucrose, the sugars are chemically bonded to make a disaccharide.  The ratio of fructose-to-glucose is 50:50 in sucrose, and either 55:45 or 42:58 in HFCS.  The bonded vs unbonded condition and slightly different ratios of fructose and glucose at one time were postulated to be significant differences between sucrose and HFCS, however, comparative studies have shown that the human body cannot distinguish them.

 

HFCS and sucrose are also equivalent in energy (approximately 4 kcalories/gram), sweetness and metabolism.  Controlled clinical trials have demonstrated that HFCS and sucrose are equivalent by every metabolic parameter yet measured including serum glucose and insulin, the appetite hormones ghrelin and leptin, triglycerides, uric acid and sensory measures of appetite and satiety.

 

Finally, HFCS and sucrose are similar in manufacture.  In order to ensure they are of suitable purity for use in foods and beverages, both are purified and refined using common manufacturing methods.  And both qualify as natural ingredients under FDA guidelines.