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Back to Experts' Summaries

Protein Requirements: Time to Re-evaluate Canadian Recommendations

Current recommendations for protein are 0.8 g/kg/day for adults and 0.95 g/kg/day for children. However, recent studies using the Indicator Amino Acid Oxidation (IAAO) technique clearly indicate the Recommended Dietary Allowance (RDA) should be substantially higher.

Ronald O. Ball Ronald O. Ball, PhD

Professor Emeritus, Department of Agriculture, Food and Nutritional Sciences, University of Alberta

Highlights:

  • Current recommendations for protein may not meet the needs of Canadians.
  • Protein requirements appear to be 33% and 63% higher for adults and children, respectively.
  • Good sources of high-quality protein include milk products, eggs, meat, fish and poultry.

Nitrogen balance method

The nitrogen balance method (nitrogen balance = nitrogen intake – nitrogen excretion) currently used to determine protein requirements is inaccurate for a number of reasons. It tends to overestimate nitrogen intakes and underestimate nitrogen excretion, thereby generally yielding an overall underestimation of nitrogen balance and, hence, protein requirements.

IAAO method

Two studies conducted by our group used the IAAO method developed by Ball and Bayley to determine protein requirements in healthy young men (26.8 ± 2.0 yrs; n=8)1 and boys and girls (6-11 yrs; n=7).2 The advantages of this technique over the nitrogen balance method are threefold:1

  • It does not determine nitrogen balance, the determination of which is technically demanding, but instead responds rapidly to in vivo changes in rates of protein synthesis;
  • It allows study of the same individual over an entire range of protein intakes, thus decreasing between-individual variability; and
  • It is noninvasive and can be used to determine accurate protein requirements regardless of the subject’s age or medical condition.

Both studies indicate that current protein recommendations are too low and require reassessment.

  • In the adult study, participants were randomly assigned to receive seven graded protein intakes (range: 0.10-1.8 g/kg/d) as a crystalline amino acid mixture.

The study showed that the population-safe protein requirements were 1.2 g/kg/d, 33% higher than current recommendations.1

  • Similarly, the children were randomized to receive a minimum of seven protein intakes (range: 0.1-2.56 g/kg/d). Protein was provided as an amino acid mixture. We determined that the population-safe protein requirements were 1.55 g/kg/d, 63% higher than current recommendations.2

Keywords: protein


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