IAFNS Protein Spring Committee Meeting

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.

Protein Quality Measurement Approach in North America

Protein quality has not been an issue in North America populations in the recent past due to the quantity and quality of protein consumed. However, as food sources shift, quality of protein may become a more important consumer decision factor in their individual choice of foods. This proposed in vitro protein digestibility method will provide an alternative to replace animal testing as an immediate, scientifically, and ethically sound approach to encourage more food manufacturers to measure and maintain protein quality in foods being developed with plant and alternative protein sources in North America.


Institution: University of Manitoba

Principal Investigator: Dr. James House

Year: 2022

This work was supported by the IAFNS Protein Committee.

Specific Essential Amino Acid Intakes and Health Benefits Among Older Adults

Protein and specific amino acid intakes are among the lifestyle factors that can mitigate muscle loss among older adults. Lean mass is associated with metabolic and functional health in older age. Clear linkages between specific amino acids and health outcomes will inform future recommended intakes. Furthermore, comparing the composition of essential amino acids in differing eating patterns (recommended as well as popular trends) can identify opportunities to improve essential amino acid intakes.

Institution: Florida State University
Principal Investigator: Claire Berryman, PhD
Year: 2020

Read More: Amino Acid Intake And Conformance With The Dietary Reference Intakes In The United States: Analysis Of The National Health And Nutrition Examination Survey, 2001–2018

View this project on the Center for Open Science’s Open Science Framework.

This work was supported by the IAFNS Protein Committee.

Protein Intake and Human Health: Implications of Units of Protein Intake

Current dietary recommendations for protein intake are expressed as grams per kilogram of body weight in recognition of its role as the structural building blocks for lean body mass. Although FAO/WHO acknowledges that this recommendation is appropriate for those in the ideal weight-for-height ranges, it may not be appropriate for those who are overweight. This project will demonstrate a method to express protein intake in nutrition studies that removes confounding among overweight individuals.

Institution: Tufts University
Principal Investigators: Adela Hruby, PhD, MPH; Paul Jacques, DSc
Year Awarded: 2019

Read more: Protein Intake and Human Health: Implications of Units of Protein Intake

Learn more about the IAFNS Protein Committee.

Nutrient Adequacy and Diet Quality in a Randomized Controlled Trial with Normal and Higher Protein Intake

Foods that are high in protein are often rich in other nutrients that are unique to specific categories of foods (e.g., iron in red meat, vitamin E in nuts). When individuals select a protein-containing food on a calorie-controlled diet, it is at the expense of other foods in the diet. It is unclear what foods or categories of foods are being displaced with higher dietary protein intakes, and what the impact of this is on overall diet quality. The aim of this study is to evaluate nutrient intakes and overall diet quality in women assigned to self-select a higher and normal protein diet during a one-year weight loss intervention.

Institution: Rutgers University
Principal Investigator: Sue Shapses, PhD, RD
Year Awarded: 2018

Read more:

Higher Protein Intake During Caloric Restriction Improves Diet Quality And Attenuates Loss Of Lean Body Mass

View this project on the Center for Open Science’s Open Science Framework.

Learn more about the IAFNS Protein Committee.


Protein Intake and Healthy Aging

Aging is associated with many physiological and metabolic changes. The role of dietary protein in aging has focused largely on musculoskeletal aging; however, protein may also have implications for age-related physiological functional changes beyond muscle and bone. The aim of this study is to assess the importance of protein intake in mid-life to healthy aging.

Institution: USDA Jean Mayer Human Nutrition Research Center on Aging
Principal Investigator: Paul Jacques, DSc
Year Awarded: 2015

Read more:

Dietary Protein and Changes in Biomarkers of Inflammation and Oxidative Stress in the Framingham Heart Study Offspring Cohort

Protein Intake and Functional Integrity in Aging: The Framingham Heart Study Offspring

Dietary Protein and Changes in Markers of Cardiometabolic Health Across 20 Years of Follow-Up in Middle-Aged Americans

Learn more about the IAFNS Protein Committee.