Cellulose gum
Cellulose gum is extracted from wood pulp and cotton cellulose. The resulting powder can absorb up to 20 times its starting weight. Only the purest cellulose gum is fit for human consumption; the rest gets put into shampoo or other non-edible things. Typically used to thicken or bind things. Cellulose, gum or not, cannot be properly digested by humans. It does not contain any health benefits.