Estimation of Protein Requirements

ESTIMATION OF PROTEIN REQUIREMENTS

The following methods can be used to estimate protein requirements based on life stage. Use of actual body weight or when weight cannot be obtained, ideal body weight (IBW), is suggested for all equations because protein requirements relate to lean body mass. In the underweight, malnourished patient, use of actual body weight has been suggested in equations using anabolic protein levels in order to avoid the consequences of overfeeding in these patients. A nitrogen balance test may be employed to evaluate adequacy of protein intake in either obese or undernourished patients.

Grams per kilogram

Maintenance: Recommended Dietary Allowances (RDA): 0.8 to 1.0 g/kg ideal weight (1)

Anabolism:
Critical illness and hypermetabolism is associated with increased protein turnover, protein catabolism, and negative nitrogen balance (2). Protein requirements double in critical illness to approximately 15% to 20% of total calories (2). Current practice dictates that energy requirements be provided to meet energy demands as determined by appropriate energy equations or indirect calorimetry and protein intakes between 1.1 g to 1.5 g/kg (2,3). Higher requirements may be required in acute trauma and burn patients (3). See below for current recommendations.

Critical Illness/Moderate Stress: 1.1 to 1.5 g/kg (2,3)

Trauma/Burn: 1.5 g/kg to 2.0 g/kg (3). Refer to Burns

Spinal Cord Injury: The acute phase of spinal cord injury results in an obligatory negative nitrogen balance that may persist for 7 weeks or more, as nitrogen excretion increases with changes in body weight and loss of lean body mass (4). Efforts to achieve positive nitrogen balance with aggressive nutrition support are generally unsuccessful and may result in overfeeding (4). Although a protein intake of 2.4 grams/kg IBW/day may lessen the negative nitrogen balance, 2 g protein/kg IBW/day may be more appropriate given potential concerns of substrate overload (Grade III) (4). Acute phase hypoalbuminemia may not be indicative of malnutrition, but a rising albumin level within 3 weeks of injury generally indicates adequate nutritional intake (4). For a person with spinal cord injury, 0.8 - 1.0 g protein/kg body weight/day may be required for maintenance, with an increase to 1.0 - 1.5 g protein/kg body weight/day if pressure ulcers or infection are present (Grade III)(4).

Refer to Criteria and Dietary Reference Intake Values for Protein by Life Stage Group for disease-specific information.

References

Institute of Medicine’s Food and Nutrition Board. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academy of Sciences, 2002: 265-334; preprint at http://www.nap.edu.books/0309085373/html/index.html, accessed September 16, 2002.
Young L, Kearns LR, Schoepfel SL. Protein. In: Gottschlich MM ed. The A. S. P. E. N. Nutrition Support Core Curiculum: A Cased-Based Approach- The Adult Patient. Silver Spring, MD: American Society of Enteral and Parenteral Nutrition; 2007:82-83.
Jacobs DG, Jacobs DO, Kudsk KA, Moore FA, Oswanski MF, Poole GV, Sacks G, Scherer LR 3rd, Sinclair KE: East Practice Management Group. Practice management guidelines for nutrition support of the trauma patient. J Trauma. 2004;57:660-679 .
Spinal Cord Injury Evidence Analysis Project. American Dietetic Association Evidence Analysis Library. American Dietetic Association; 2007. Available at: http://www.adaevidencelibrary.com. Accessed November 7, 2007.