Intact Protein Versus Free Amino Acids in the Nutritional Support of Thermally Injured Animals

Abstract

This study compared the nutritional effects of intact protein with that of constituent amino acids as the sole source of nitrogen in a burn guinea pig model. Forty-five guinea pigs bearing a gastrostomy feeding tube were given 30% total body surface area, full thickness flame burn and were randomized into four groups. Group I (n = 12) and group III (n = 15) received a diet containing whey protein, while group II (n = 9) and group IV (n = 9) received an otherwise identical diet containing free amino acids in a whey protein pattern. Full strength continuous intragastric feeding was initiated immediately postburn in groups I and II, but a 72-hr adaptive period was provided in groups III and IV. Resting metabolic expenditure was measured by indirect calorimetry on postburn days 2, 6, 9, and 13. After 14 days of enteral feeding, the animals were killed. Immediate enteral feeding of intact protein or free amino acids reduced postburn hypermetabolic response (p < 0.01). However, the intact protein was found to maintain body weight and provide nitrogen retention better than the amino acid mixture (p < 0.05). The animals on the intact protein diet also showed statistically significant benefits in carcass, liver, and gastrocnemius muscle weights and in serum albumin, transferrin and C3 levels. It is concluded that intact protein is superior to free amino acids for nutritional support following burn injury. (Journal of Parenteral and Enteral Nutrition 10:139-145, 1986)