Saunders D R, Wiggins H S
Am J Physiol. 1981 Nov;241(5):G397-402. doi: 10.1152/ajpgi.1981.241.5.G397.
We measured fecal composition after giving oral doses of mannitol, lactulose, or raffinose to ileostomy patients and to normal subjects in order to determine the colon's capacity for metabolizing these carbohydrates and to decide whether volatile fatty acids (VFA) or unabsorbed carbohydrate initiated diarrhea. Seventy-four percent of mannitol, 100% of lactulose, and 88% of raffinose passed unabsorbed through the small intestine of six patients with ileostomies. Dose-response experiments revealed that normal subjects could tolerate 120-220 mmol of mannitol, 73-146 mmol of lactulose, or 80 mmol of raffinose before fecal output of water exceeded 400 ml in 48 h or before test carbohydrate appeared in the stool. Mannitol could be metabolized to glucose; lactulose to fructose, galactose, and glucose; and raffinose to sucrose, melibiose, fructose, galactose, and glucose. The output of VFA in fecal water did not correlate with the moles of carbohydrate metabolized, and it did not greatly exceed the output of VFA in stools of equal volume that were induced by nonfermentable MgSO4. We conclude that the human colon is capable of removing appreciable amounts of single doses of these carbohydrates from fecal water. When this capacity is exceeded, unabsorbed carbohydrate rather than VFA prompts an increased output of fecal water.
我们给回肠造口术患者和正常受试者口服甘露醇、乳果糖或棉子糖后测量粪便成分，以确定结肠代谢这些碳水化合物的能力，并确定是挥发性脂肪酸（VFA）还是未吸收的碳水化合物引发腹泻。6名回肠造口术患者中，74%的甘露醇、100%的乳果糖和88%的棉子糖未被吸收而通过小肠。剂量反应实验表明，在48小时内粪便水分排出量超过400毫升之前或试验性碳水化合物出现在粪便中之前，正常受试者能够耐受120 - 220毫摩尔的甘露醇、73 - 146毫摩尔的乳果糖或80毫摩尔的棉子糖。甘露醇可代谢为葡萄糖；乳果糖可代谢为果糖、半乳糖和葡萄糖；棉子糖可代谢为蔗糖、蜜二糖、果糖、半乳糖和葡萄糖。粪便水中VFA的排出量与代谢的碳水化合物摩尔数无关，且其排出量并未大大超过由不可发酵的硫酸镁诱导产生的等体积粪便中VFA的排出量。我们得出结论，人类结肠能够从粪便水中清除相当数量的单剂量这些碳水化合物。当这种能力被超过时，未吸收的碳水化合物而非VFA会促使粪便水分排出增加。
