Psyllium husk is the husk of the seed of the plantain plantago ovata and is a concentrated source of dietary fibre 80 water soluble fibre composed mostly of hemicellulose it is not digested in the small intestine but partially broken down in the colon where it acts as a food source for friendly flora psyllium acts as a sponge in the intestinal tract swelling as it absorbs water toxins and waste material