Vegetable glycerin (also known as glycerol) is a sugar alcohol used in small quantities as sweetener. It has 60% the sweetness of table sugar (sucrose). For human consumption, glycerin is classified by the U.S. FDA as a caloric macro-nutrient. Vegetable glycerin has a positive heat of solution, feeling warm when ingested. When mixed with sugar alcohols like erythritol which have a negative heat of solution, glycerin counteracts their cooling effect.
Vegetable glycerin acts as a preservative. It's commonly used for alcohol-free liquid extracts called glycerites. Glycerites are normally prepared with 1 part water and 1 part vegetable glycerin. The 1:1 ratio of water to vegetable glycerin ensures that the extract is properly preserved.
Medicinally, in adults, the maximum safe dosage is 120 grams per day (Gilman et al, 1990).
Effects On Enzymes
In vitro tests found that glycerin induces CYP2E1.[2][1] Human CYP2E1 was increased 250-300% after 4-8 hours.[1] The half life of CYP2E1 was also increased 366% (from 3 hours to 11 hours) after treatment with glycerin.[1] These results have yet to be verified clinically in human volunteers.