Hydration is part of fibre behaviour
Fibre and water belong together. This is especially true for water-holding and gel-forming fibres. When fibre absorbs water, it swells. That swelling is part of how it softens stool, creates bulk, and changes texture inside the gut.
Without enough water, fibre may not behave comfortably. A sudden jump in fibre with poor hydration can feel heavy, gassy, or difficult. A better pattern is slower: add fibre-rich foods steadily, drink enough water, and notice tolerance. Water helps fibre work. Fibre helps water stay useful inside digestion. The gain is not dramatic. It is better daily handling. That is the practical partnership.