While visiting the United States from Argentina this month, I have become quite interested in the debate over sweeteners and more specifically agave nectar. When I left the U.S. four years ago, agave nectar was the newest craze.  Many, including myself, were excited about its low glycemic index and potential as a healthy (or healthier) sweetener than other natural sugars on the market. Companies started mass-producing this alternative sweetener and promoting it as an ideal sugar substitute for...