Blood-sugar and calorie concerns have people looking to new sugar substitutes. Agave nectar has a low-glycemic index and doesn't induce a sugar high, but it is a form of fructose that raises triglyceride levels in the blood. Stevia is derived from a plant and 300 times sweeter than sugar, has no calories and no carbs. It works in drinks, puddings and pie fillings. Xylitol is a sugar alcohol, low in calories with little effect on blood-sugar levels, but it can cause digestive problems.