[Nutritional requirements and parenteral feeding]

1. The nutritional needs of man are governed by the law of the minimum (structural and protective substances) and the isodynamic rule (exchangeability of various energy carriers) There is a tendency to abandon the traditional concept of requirement as an absolute value (g or mg/day) and replace it by 3 graded parameters (minimal - lowest acceptable - desirable supply). Today nutrient density is of utmost importance in the planning and evaluation of food formulas, i.e. the content per 1000 kcal or per MJ = mega-Joule. 2. The metabolism of nutrients proceeds (simplified) in 3 phases: a) digestion (comminution); b) coordination and conversion in intermediary metabolism; c) direct use in synthetic or oxidation processes. This creates problems of balance, of co-ordination and regulation. In the phases b and c the same conformities apply for oral and parenteral feeding. 3. Particular features of parenteral feeding: Exclusion of intestinal flora, limited capacity of uptake by the circulation and, especially, the lowered capacity of biochemical regulatory mechanisms (homeostasis) in patients requiring parenteral feeding necessitate optimal coordination of supply and effective needs. Attempts to comply are made by continuous infusions, diversification of the substrate supply and optimisation of the different components. In principle, priority is given to those nutritional factors which promote anabolism (tissue formation) and counteract catabolism (tissue breakdown). 4. Example: protein needs. --Recapitulation of quantitative and qualitative requirements regarding protein and amino acid supply. --Discussion of the different recommendations and guidelines. --Discussion of the criteria for evaluation and the composition of an optimal amino acid mixture (nitrogen balance and growth as criteria). 5. Conclusions for parenteral feeding. The supply of amino acids should be on the generous side because there is an increased requirement in the "acute phase" and in convalescence. The amino acid composition should correspond to the pattern of a high quality food protein. The E/T ratio (essential AS versus total AS supply) is an indicator. The value proposed as a guideline is E/T approximately 3. However, an exaggerated amino acid cosmetic is not recommended. 6. Diagnostic problems. In the interest of optimal results of treatment, foremost attention should be given to the detection of latent deficiency states and the improvement of nutrition at large. The list of indicators given in the figures should be consulted whenever there is evidence of undersupply. The so-called "hospital malnutrition", as described in recent studies, should obviously not occur.