Erythritol is a low calorie, low carb, gluten-free sugar substitute used by many dieters. Erythritol is naturally found in fruits, vegetables and fermented foods. Erythritol has a GI of 0 and 0.2 calories per gram. It does not affect blood sugar and is suitable for a low-carb diet. Its sweetness is about 0.7 of sugar and you may need to use a bit more than sugar.