Medical and surgical stress (major surgery, sepsis, injuries,...) increases requirements of certain essential nutrients and others considered non-essential or semi-essential. 2. Some nutrients such as glutamine, arginine, omega 3 fatty acids nucleotides, ... have a considerable influence on the immune function (delayed hypersensitivity, lymphocyte sub-population counts, immunological tests,..) and improve certain metabolic and nutritional indices (nitrogen balance, medium and short life proteins,...). For this reason, they are called "immunonutrients" or "immunity regulators". 3. The supply of special enteral formulas for situations of immunological compromise, with the addition of one or more of the nutrients considered today as "immunity regulators" has increased since 1988 in both absolute and percentage terms. 4. These nutrient-enriched enteral formulas improve the rate of infections, reduce the number of days on ventilator equipment, the length of hospital stays for critical patients, with a more marked effect on surgical patients. 5. The evidence seems today to support the use of enriched formulas with critical patients. Nonetheless, some caution must be maintained as it has not been possible to show any reduction in the mortality of the cases studied nor, in short, in the prognosis of patients affected by situations of hypercatabolism and reduced immunity. 6. We feel that their use should, therefore, be carried out in accordance with the protocols and in patients expected to survive, where the evolution reveals severe catabolism unhindered by conventional therapy.
