Clinical nutrition: commercially or clinically essential?

Laboratoire de Biochimie A Hopital Hotel Dieu 1 Place du Parvis Notre Dame F-75181 Paris Cedex 04 France E-mail: luc.cynober{at}htd.ap-hop-paris.fr.Biol.

Dear Sir:

In a recent "Special Article" in the Journal, Buchman (1) has yet again (2) expressed his views on the use of glutamine-supplemented diets in clinical nutrition. However, I am concerned about his lack of objectivity in many of the examples proposed in his paper. For example, he 1) confuses the results of poorly designed studies with those of well-designed studies, 2) refutes the results of well-designed studies by emphasizing their minor methodologic weaknesses, 3) states that particular studies have flaws but does not substantiate these flaws, 4) combines the results of studies of the effects of enteral and parenteral nutrition even though the differences in glutamine's effects with the route of administration were emphasized in a remarkable analysis (3), 5) does not mention the results of some important studies that do not support his conclusions, and 6) says that the results of experimental studies should not be considered in the discussion of glutamine's effects; however, he cites such studies when it suits his purpose. From Buchman's review, it would have been just as easy to conclude that enteral nutrition has no advantage over parenteral nutrition, that parenteral nutrition is not efficacious in perioperative nutrition, that the usefulness of early enteral nutrition remains to be shown, or that fiber is not efficacious in enteral nutrition.

In particular, the author calls ornithine -ketoglutarate a glutamine precursor (4). However, in an important paper published in this Journal coauthored by Buchman, ornithine -ketoglutarate administration restored growth in infants receiving long-term total parenteral nutrition (5). Three different studies indicate that ornithine -ketoglutarate improves wound healing in burn patients (6–8). One can argue that the effects of ornithine -ketoglutarate are not mediated by glutamine. This is possible but not certain (9,10). In any case, the literature supporting this finding should have been considered by Buchman.

What does "commercially essential" in the title of Buchman's article mean? Available products are marketed by companies whose job it is to make money, which permits a reinvestment in research.

REFERENCES

1. Buchman AL. Glutamine: commercially essential or conditionally essential? A critical appraisal of the human data. Am J Clin Nutr 2001;74:25–32.
2. Buchman AL. Glutamine: is it a conditionally required nutrient for the human gastrointestinal system? J Am Coll Nutr 1996;15:199–205.
3. Alpers DH. Is glutamine a unique fuel for small intestinal cells? Curr Opin Gastroenterol 2000;16:155–9.
4. Le Bricon T, Cynober L, Baracos VE. Ornithine -ketoglutarate limits muscle protein breakdown without stimulating tumor growth in rats bearing Yoshida acites hepatoma. Metabolism 1994;43:899–905.
5. Moukarzel AA, Goulet O, Salas JS, et al. Growth retardation in children receiving long-term total parenteral nutrition: effects of ornithine -ketoglutarate. Am J Clin Nutr 1994;60:408–13.
6. De Bandt JP, Coudray-Lucas C, Lioret N, et al. A randomized controlled trial of the influence of the mode of enteral ornithine alpha-ketoglutarate administration in burn patients. J Nutr 1998;128:563–9.
7. Donati L, Ziegler F, Pongelli G, Signorini MS. Nutritional and clinical efficacy of ornithine alpha-ketoglutarate in severe burn patients. Clin Nutr 1999;18:307–11.
8. Coudray-Lucas C, Le Bever H, Cynober L, De Bandt JP, Carsin H. Ornithine alpha-ketoglutarate improves wound healing in severe burn patients: a prospective randomized double-blind trial versus isonitrogenous controls. Crit Care Med 2000;28:1772–6.
9. Le Boucher J, Cynober L. Ornithine alpha-ketoglutarate: the puzzle. Nutrition 1998;14:870–3.
10. Le Boucher J, Farges MC, Minet R, Vasson MP, Cynober L. Modulation of immune response with ornithine alpha-ketoglutarate in burn injury: an arginine or glutamine dependency? Nutrition 1999;15:773–7.