Trehalose is Generally Regarded as Safe GRAS and for the vast majority of humans is well tolerated.  There are however a significant number of people (8%) of people from Greenland and Iceland who appear to suffer with a  missing enzyme, Trehalase, which is involved and essential in order for the body to break diown trehalose into Glucose. People with Trehalase deficiency are unable to break down Trehalose and will present with mild diarrhoea after ingestion. In the rare event that this occurs please discontinue use of Trehalose. The effects will pass quickly and are not injurious to health.