a stillsuit is a "body-enclosing garment" of Fremen design which performs the "functions of heat dissipation and filtering bodily wastes", as well as retaining and reclaiming moisture
For this question, I am interested into reclaiming property of this suit. The book argues about the fact that the losses were virtually only due to exposed skin.
However, I am wondering if the human body is actually consuming (through biochemical reactions) any water or it is used entirely as a dissolvent or maybe as a catalyst), so that its loss entirely depends on the ability of reclaiming it externally.
Question: Does human organism consume water or is it only used as solvent?