Department of Gastroenterology, Chiba Hokusoh Hospital, Nippon Medical School, Chiba 270-1694, Japan.
World J Gastroenterol. 2021 Dec 7;27(45):7784-7791. doi: 10.3748/wjg.v27.i45.7784.
The cell walls of plants are mainly made of cellulose and contain a large number of calories. However, the main component, cellulose, is an indigestible plant fiber that is thought to be difficult for humans to use as energy. Herbivores acquire energy through the degradation of cell wall-derived dietary fiber by microorganisms in the digestive tract. Herbivores, especially horses, have a highly developed cecum and large intestine, and plants are fermented for their efficient use with the help of microorganisms. Humans also have an intestinal tract with a wide lumen on the proximal side of the large intestine, in which fermentation occurs. The digestive process of horses is similar to that of humans, and many of the intestinal bacteria found in horses that degrade plants are also found in humans. Therefore, it is thought that humans also obtain a certain amount of energy from cell wall-derived dietary fiber. However, the intake of dietary fiber by modern humans is low; thus, the amount of calories derived from indigestible plant fiber is considered to be very low. Cellulose in the plant cell wall is often accompanied by hemicellulose, pectin, lignin, suberin, and other materials. These materials are hard to degrade, and cellulose is therefore difficult for animals to utilize. If the cell wall can be degraded to some extent by cooking, it is thought that humans can obtain calories from cell wall-derived dietary fiber. If humans can use the calories from the cell wall for their diet, it may compensate for human food shortages.
植物细胞壁主要由纤维素组成，含有大量热量。然而，主要成分纤维素是一种不可消化的植物纤维，据认为人类很难将其用作能量。食草动物通过微生物在消化道中降解细胞壁衍生的膳食纤维来获取能量。食草动物，尤其是马，具有高度发达的盲肠和大肠，在微生物的帮助下，植物可以发酵以供高效利用。人类的大肠近端也有一个腔宽大的肠道，其中也会发生发酵。马的消化过程与人类相似，在马体内发现的许多能够降解植物的肠道细菌也存在于人类体内。因此，人们认为人类也可以从细胞壁衍生的膳食纤维中获得一定量的能量。然而，现代人膳食纤维的摄入量很低；因此，人们认为从不可消化的植物纤维中获得的卡路里数量非常低。植物细胞壁中的纤维素通常与半纤维素、果胶、木质素、软木脂和其他物质一起存在。这些物质很难降解，因此纤维素也很难被动物利用。如果通过烹饪可以在一定程度上降解细胞壁，人们认为可以从细胞壁衍生的膳食纤维中获取卡路里。如果人类可以将细胞壁的热量纳入饮食中，这可能可以弥补人类的食物短缺。
