Health and Functional Effects of Dietary Protein Beyond Protein Turnover

As food systems and consumer food preferences evolve toward replacing animal protein with alternative protein sources, it is imperative to understand the long-term health consequences. This project aims to prioritize research approaches and ultimately food decisions that take into consideration evidence linking the impact of dietary protein and amino acid intakes on meaningful functional outcomes among the general adult population. Since growth is not the priority outcome among adults, it is imperative to prioritize health outcomes as well as the indicator measures that are meaningful to drive food formulation and consumer choices

Data generated from nearly three decades of highly-controlled laboratory studies evaluating the effects of dietary protein intake on isotopic measures of protein turnover serve as the basis for many contemporary dietary recommendations. For example, recommendations that advocate for equally distributing dietary protein intake across meals, how much to consume with each meal, post-exercise, and the amount necessary to overcome age-related anabolic resistance were all derived from acute tracer studies quantifying muscle protein synthesis in response to ingesting isolated intact proteins, free-form amino acids, or protein-containing foods or mixed-meals. However, studies leveraging the acute stimulatory effects of varying dietary protein manipulations on muscle protein synthesis to augment muscle mass and physical function over time have yielded mixed results (i.e., minimal to no benefit). The inability to extend findings from acute laboratory studies to long-term benefit can be attributed to costs, experimental limitations, inadequate controls, compliance, attrition, and the inherent variability in diet protein-related health outcomes such as body composition and physical function. The discrepancies between acute and long-term trials raise practical concerns that question the extent to which manipulating protein intake beyond current requirements provides tangible health benefits.

The project explores gaps related to alternative measures of how protein affects human health and what health outcomes, beyond tracer measures of protein turnover and body composition, should be the focus for new research to advance dietary protein research.


Institution: Eastern Michigan University together with additional experts from multiple institutions

Principal Investigator: John Carbone

Expert Writing Group:
John Carbone, Eastern Michigan University
Stefan Pasiakos, NIH
Connie Weaver, San Diego State University
Wayne Campbell, Purdue
Heather Leidy, Univ Texas Austin
Stu Phillips, McMaster University

Year: 2023

This work is supported by the IAFNS Protein Committee.