Erythritol is an almost 0 calorie / low-glycemic sugar substitute

Overview

Erythritol is a fermented sugar alcohol (aka polyol).   Occurs naturally in, for example, pears,melons, grapes, mushrooms and fermentation-derived foods such as wine, soy sauce and cheese. Commercial erythritol is derived from corn. Other sugar alcohols include xylitol, maltitol, sorbitol and lactitol.

Used as a bulk sweetener in low calorie foods. Typical retail cost of erythritol is ~ $6-9 per pound - considerably more expensive than table sugar.

Looks and tastes like table sugar (sucrose).  This white crystalline powder can be used measure for measure as a direct substitute for sugar in recipes. Available in both granulated and powdered forms. Erythritol is about 70% as sweet as sugar and is reported to have no aftertaste.

Almost zero calories - 0.24 calories per gram. i.e. <1 calorie / teaspoon (compared to sugar's 16 calories / tsp. or honey's 22 calories / tsp.) E.g. 1 tsp. (4.18 g) crystalline powder erythritol has ~ 1 calorie.

Does not cause tooth decay - erythritol resists metabolization by oral bacteria, which can break down sugars and starches to produce acids which may lead to tooth enamel loss and cavities.

Kawanabe, J.; Hirasawa, M.; Takeuchi, T.; Oda, T.; Ikeda, T. (1992). "Noncariogenicity of erythritol as a substrate".Caries Research26(5): 358-62.PMID1468100

Safe dosage - study shows spread out daily consumption of 1 gram / kilogram body weight of erythritol in various foods and beveragesis well tolerated by adults as compared to sucrose containing foods.

And yet - Erythritol is associated with weight gain

A 2015 study of 172 healthy freshman, led by Cornell University researchers in the Division of Nutritional Sciences and researchers at Braunschweig University of Technology, Germany, and the University of Luxembourg, has identified the sugar alcohol erythritol as a biomarker for increasing fat mass and can be metabolized by (and even produced in) the human body. Erythritol (which this study found could be synthesized  by the body from glucose) was elevated at the beginning of the year in freshmen who went on to gain weight, fat, and abdominal fat compared with freshmen with stable weight.

"Erythritol is not consumed and released from the body unchanged; it has an impact on the metabolism of our body. This finding is in contrast to all previous assumptions."

-- Senior co-author Karsten Hiller, professor of bioinformatics and biochemistry at TU Braunschweig and a leading scientist in cellular metabolism

Researchers found that students who gained weight and abdominal fat over the course of the year had 15 times higher blood erythritol at the start of the year compared with their counterparts who were stable or lost weight and fat mass over the academic year.

Side Effects of using erythritol

In moderation, erythritol doesn't cause digestive upset /diarrhea like some of the other sugar alcohols - being a smaller molecule than xylitol, maltitol and sorbitol,for example, allows it to be 90% absorbed in the small intestine and then excreted mostly unchanged in the urine. It is not fermented by intestinal bacteria.

Arrigoni, E.; Brouns, F.; Amadò, R. (November 2005)."Human gut microbiota does not ferment erythritol"(pdf).British Journal of Nutrition94(5): 643-6..PMID16277764

Erythritol should not cause digestive upset in most people unless consumed in large quantities over 50 grams (~2 ounces) - although some people can have digestive issues even with small amounts.