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A randomized prospective double-blinded study was conducted in patients in moderate to high level surgical stress to ascertain the effect of high dose branched-chain (BcAA) hyperalimentation on skin test reactivity and lymphocyte count. Isocaloric, isonitrogenous balanced total parenteral nutrition solutions were administered to two treatment groups. The study group received the high dose (45% BcAA) solution while the control group received a standard amino acid solution (24.2% BcAA). All patients received 1 to 1.5 g/kg/day of amino acids and 30 nonprotein cal/kg/day, with 30% of them as fat. Immune function was assessed by absolute lymphocyte count and delayed cutaneous hypersensitivity on days 0 and 7 of therapy. Absolute lymphocyte count showed a marked improvement in patients receiving high dose aBcAA (p less than 0.03). All patients were anergic at baseline; a much greater percentage of skin test reactivity was observed in the BcAA group on day 7 (p less than 0.03). They were also in positive nitrogen balance. The data suggest that improved nitrogen retention and immune-competence is possible with branched-chain-enriched hyperalimentation in high level surgical stress.

In recent years, evidence has accumulated on the effects of nutrients on metabolic processes. The role of specific nutrients in modulating immune function has received much attention because of the significant role of the immune system in a variety of disease states. The immune system depends on the complex interactions of its various parts. In response to an "antigen" or foreign substance that penetrates the external protective barriers of the human body, nonspecific (phagocytes, complement) defense mechanisms and antigen-specific factors are activated. The antigen-specific immune system relies on both humoral (antibodies and B cells) and cellular (T cells and lymphokines) defenses. Malnutrition causes a decline in all aspects of host defense. Correction of malnutrition in hospitalized patients and restoration of immunocompetence has become a goal of nutrition support practitioners today. The application of current research findings to patient care requires a basic understanding of immunology.