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Elemental diets: Are they “diets” or “drugs”?
ARTICLE IN PRESS Clinical Nutrition (2006) 25, 706–707
http://intl.elsevierhealth.com/journals/clnu
CORRESPONDENCE Elemental diets: Are they ‘‘diets’’ or ‘‘drugs’’? Dear Editor, I read with interest the paper by McGough et al.1 in the February issue of Clinical Nutrition and I completely agree with the conclusions the Authors have drawn from their well-conducted investigation. In my opinion what is open to discussion is the scientific rationale of the study. If we go back to the history of the potential role of the elemental diets (ED) in preventing the radiation enteropathy, we have to accept that it relies on the following points: (1) Since the early 1970s Bounous extensively investigated on dietary protection during radiation therapy and in this excellent review2 he stated that the probable prophylaxis afforded to the irradiated intestine is due to the reduction in pancreaticobiliary secretions, which play an important role in the initial assault on the mucosa during injury. (2) In the same period Morgenstern et al.3 showed experimentally that neutralization of pancreatic and intestinal proteases, diversion of the abrasive bulk of the intestinal content4 or ligation of the pancreatic duct5 significantly modify the response to radiation by preventing mucosal sloughing. (3) ED contain most nutrients in their simple molecular form to enable passive absorption with minimal stimulation of biliary and pancreatic secretions, while they are able to decrease the rate of crypt cell turnover.6 So they would work combining a double effect: on one hand they decrease the activity of those enzymes which facilitate disruption of the glycocalyx, a crucial barrier to noxious intestinal agents, while maintaining some trophism of the mucosa, on the other hand they decrease the vulnerability of the intestinal epithelium to radiation which strictly depends on crypt cell mitotic activity.
It appears that this particular type of bowel rest (and the additional benefits) can be achieved only if ED represent in toto the nutritional support, because here we are not dealing with the pharmacologic effect of some substrates which can be administered as a ‘‘supplement,’’ but with a type of nutrition that ‘‘totally replaces’’ the traditional one. As a matter of fact, several studies in animals exclusively fed with an ED were successful in preventing damages of the radiation enteropathy, whereas all the studies published in literature on humans (including the present one) utilized ED as a supplementation and were negative. The only exception was the study by McArdle et al.7 where patients were fed exclusively with an ED at 1600–2000 kcal by mouth or through a nasoduodenal or a fine-needle jejunostomy. At variance with the control group, in the ED patients histologically and ultra structurally biopsy specimens of the ileal mucosa were normal, with maintenance of the normal levels of enzyme activity in the brush border, and severe or bloody diarrhea was absent. Since patients reported in the McGough’s paper1 had probably an energy requirement of 20–25 kcal/ kg/day we can expect their energy requirement were met, depending on their BMI, with a daily calorie intake of about 1500–1850 kcal, which corresponds to a volume of ED of 1700–2150 mL. This amount roughly exceeds by 5–6 times the best volume the patients were able to consume in the first week of radiotherapy. In conclusion, I acknowledge the fact the authors have brilliantly demonstrated the limited compliance of patients on radiation therapy with EDs, nevertheless I think that the potentiality of this approach should be investigated following the above-mentioned rationale.
References 1. McGough C, Balwin C, Norman A, et al. Is supplementation with elemental diet feasible in patients undergoing pelvic radiotherapy? Clin Nutr 2006;25:109–16.
0261-5614/$ - see front matter & 2006 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. doi:10.1016/j.clnu.2006.05.004
ARTICLE IN PRESS CORRESPONDENCE 2. Bounous G. The use of elemental diet during cancer therapy. Anticancer Res 1983;3:299–304. 3. Morgenstern L, Hiatt N. Injurious effect of pancreatic secretions on postradiation enteropathy. Gastroenterology 1967;53:623–9. 4. Hiatt N, Morgenstern L, Warner NE. Prolongation of postirradiation survival by diversion of intestinal content. Radiat Res 1968;35:301–10. 5. Morgenstern L, Patin CS, Krhon HL, Hiatt N. Prolongation of survival in lethally irradiated dogs by pancreatic duct ligation. Arch Surg 1970;101:586–9.
707 6. Lehnert S. Changes in growth kinetics of jejunal epithelium in mice maintained on elemental diet. Cell Tissue Kinet 1979;12:239–48. 7. McArdle AH, Reid EC, Laplante MP, Freeman CR. Prophylaxis against radiation injury. Arch Surg 1986;121:879–85.
Federico Bozzetti Hospital Misericordia e Dolce, Prato, Italy E-mail address: [email protected]
http://intl.elsevierhealth.com/journals/clnu
CORRESPONDENCE Elemental diets: Are they ‘‘diets’’ or ‘‘drugs’’? Dear Editor, I read with interest the paper by McGough et al.1 in the February issue of Clinical Nutrition and I completely agree with the conclusions the Authors have drawn from their well-conducted investigation. In my opinion what is open to discussion is the scientific rationale of the study. If we go back to the history of the potential role of the elemental diets (ED) in preventing the radiation enteropathy, we have to accept that it relies on the following points: (1) Since the early 1970s Bounous extensively investigated on dietary protection during radiation therapy and in this excellent review2 he stated that the probable prophylaxis afforded to the irradiated intestine is due to the reduction in pancreaticobiliary secretions, which play an important role in the initial assault on the mucosa during injury. (2) In the same period Morgenstern et al.3 showed experimentally that neutralization of pancreatic and intestinal proteases, diversion of the abrasive bulk of the intestinal content4 or ligation of the pancreatic duct5 significantly modify the response to radiation by preventing mucosal sloughing. (3) ED contain most nutrients in their simple molecular form to enable passive absorption with minimal stimulation of biliary and pancreatic secretions, while they are able to decrease the rate of crypt cell turnover.6 So they would work combining a double effect: on one hand they decrease the activity of those enzymes which facilitate disruption of the glycocalyx, a crucial barrier to noxious intestinal agents, while maintaining some trophism of the mucosa, on the other hand they decrease the vulnerability of the intestinal epithelium to radiation which strictly depends on crypt cell mitotic activity.
It appears that this particular type of bowel rest (and the additional benefits) can be achieved only if ED represent in toto the nutritional support, because here we are not dealing with the pharmacologic effect of some substrates which can be administered as a ‘‘supplement,’’ but with a type of nutrition that ‘‘totally replaces’’ the traditional one. As a matter of fact, several studies in animals exclusively fed with an ED were successful in preventing damages of the radiation enteropathy, whereas all the studies published in literature on humans (including the present one) utilized ED as a supplementation and were negative. The only exception was the study by McArdle et al.7 where patients were fed exclusively with an ED at 1600–2000 kcal by mouth or through a nasoduodenal or a fine-needle jejunostomy. At variance with the control group, in the ED patients histologically and ultra structurally biopsy specimens of the ileal mucosa were normal, with maintenance of the normal levels of enzyme activity in the brush border, and severe or bloody diarrhea was absent. Since patients reported in the McGough’s paper1 had probably an energy requirement of 20–25 kcal/ kg/day we can expect their energy requirement were met, depending on their BMI, with a daily calorie intake of about 1500–1850 kcal, which corresponds to a volume of ED of 1700–2150 mL. This amount roughly exceeds by 5–6 times the best volume the patients were able to consume in the first week of radiotherapy. In conclusion, I acknowledge the fact the authors have brilliantly demonstrated the limited compliance of patients on radiation therapy with EDs, nevertheless I think that the potentiality of this approach should be investigated following the above-mentioned rationale.
References 1. McGough C, Balwin C, Norman A, et al. Is supplementation with elemental diet feasible in patients undergoing pelvic radiotherapy? Clin Nutr 2006;25:109–16.
0261-5614/$ - see front matter & 2006 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. doi:10.1016/j.clnu.2006.05.004
ARTICLE IN PRESS CORRESPONDENCE 2. Bounous G. The use of elemental diet during cancer therapy. Anticancer Res 1983;3:299–304. 3. Morgenstern L, Hiatt N. Injurious effect of pancreatic secretions on postradiation enteropathy. Gastroenterology 1967;53:623–9. 4. Hiatt N, Morgenstern L, Warner NE. Prolongation of postirradiation survival by diversion of intestinal content. Radiat Res 1968;35:301–10. 5. Morgenstern L, Patin CS, Krhon HL, Hiatt N. Prolongation of survival in lethally irradiated dogs by pancreatic duct ligation. Arch Surg 1970;101:586–9.
707 6. Lehnert S. Changes in growth kinetics of jejunal epithelium in mice maintained on elemental diet. Cell Tissue Kinet 1979;12:239–48. 7. McArdle AH, Reid EC, Laplante MP, Freeman CR. Prophylaxis against radiation injury. Arch Surg 1986;121:879–85.
Federico Bozzetti Hospital Misericordia e Dolce, Prato, Italy E-mail address: [email protected]