Birch Eritritol Keto Bio 500g is a natural sweetener, which comes from the fermentation of fruits and other foods. It is a type of carbohydrate called polyols, the only one of other sugar alcohols that contains no calories and does not alter blood glucose or insulin levels. On the other hand, it helps prevent tooth decay. Erythritol is absorbed in the small intestine, but is not metabolised. It is excreted unchanged from the body in the urine.