The rate of deoxyribonucleic acid loss (DNA) from the epithelial surface of human stomach, small intestine, large intestine and skin measures the rate of cell loss. From the data it is apparent that 287 g of cells are lost every 24 h from the mucosa of the entire human gastrointestinal tract. Evidence is presented to show that in the steady-state this loss reflects the rate of production or turnover of surface epithelial cells. In atrophic gastritis, coeliac syndrome, exfoliative psoriasis and possibly ulcerative colitis turnover is high. The rate of cell loss in these diseases is high per unit of surface area. In patients with coeliac syndrome who are losing weight (active coeliacs) small bowel DNA rates are particularly high, and they fall to normal after successful treatment. There is both experimental animal, and human clinical evidence to show that in mal-absorptive states iron, protein, fat and folic acid are lost from the gut in excessive quantities. This increased endogenous loss of iron, protein and fat is related to the increased loss of DNA or cells. In the case of protein about 80 g are lost from the normal human small intestine per day, only 8–15% of which is derived from protein within cells. 12–30 g of lipid are lost per day from the human small bowel mucosa and it is virtually all derived from intracellular lipid within exfoliated epithelial cells. The term exfoliative enteropathy is suggested for this mechanism. We believe that excessive loss of endogenous material due to exfoliative enteropathy is an important cause of the malnutrition that results from diffuse diseases of the small intestine.

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