What are the plant foods that are not digested in the stomach or the small intestine?

Plant foods that are not digested in the stomach or small intestine primarily include high-fiber foods, such as whole grains, legumes, fruits, and vegetables. These foods contain cellulose and other non-starch polysaccharides that the human digestive system cannot break down. Instead, they pass into the large intestine, where some of the fiber is fermented by gut bacteria, contributing to digestive health. Additionally, certain seeds and nuts may also resist digestion due to their tough outer coatings.