A rational use of immune enhancing diets: when should we use dietary arginine supplementation?

Controversies in any arena of human activity often result in the polarization of the individuals involved into 2 opposing camps. Controversy about the use of immune-enhancing diets (IEDs) is no exception. On one hand, some groups are proposing indiscriminate use of IEDs, whereas others have created guidelines advocating that their use should be banned for the critically ill. At stake is an emerging paradigm: that dietary manipulation of the immune system is possible and may become an important adjunct to other therapies, thus helping prevent or treat multiple diseases for millions worldwide. Under these circumstances, extremist claims of miraculous benefits or inappropriate assertions of evil can only delay the emergence of a nascent science. This paper is therefore a plea for moderation from both camps, lest we cause irreparable damage to our clinical practices and potential injury to individual patients. IEDs all contain arginine. However, they also contain other substances such as omega-3 fatty acids, and nucleotides. The use of all these nutrients together into commercial IEDs without adequate evaluation of their individual effects has prevented the development of mechanistic hypotheses of action. Despite this, IEDs have been tested extensively, allowing the development of guidelines for their use. IEDs should be used for surgical patients, especially those undergoing elective surgery. IEDs show no benefit and indeed can potentially harm patients with sepsis, especially in the nonsurgical group, and should not be used outside of research protocols. Advances in basic research have helped us understand mechanisms of how arginine contained in IEDs may help surgical patients but may be deleterious in patients with sepsis. A review of the basic mechanisms of action of arginine on the immune system is enclosed in this paper and should serve as a basis for the development of scientific principles that guide clinical use of IEDs.