Making healthy choices contributes to your overall wellness. This type of supplement is usually known as a laxative. In answer to the above questions, fiber supplements are products, not food. But fiber supplements can contribute to … Insoluble fiber does not dissolve in water, and this helps food pass through the digestive system. In the large intestine, fiber can provide a laxative effect if (a) it resists fermentation to remain intact throughout the large intestine, and (b) it increases percentage of water content to soften/bulk stool (e.g., wheat bran and psyllium).