Academic and government nutrition experts say that tremendous gains have been made in the understanding of dietary protein and muscle over the past three decades, but that future studies on optimizing overall health across the lifespan would boost progress even further. 

Measures of muscle protein synthesis have led to established recommendations for protein quantity, quality, source, and timing of protein ingestion to support muscle health in older adults. 

For example, recommendations that advocate for equally distributing dietary protein intake across meals, how much protein to consume within each meal, post exercise, and the amount necessary to overcome age-related anabolic resistance were derived from research on ingesting free-form amino acids, isolated intact proteins, protein-containing foods, or mixed meals. But there’s more than just muscle in researchers’ sights now.

More Than Muscle

Instead of focusing on the minimal amount of protein to build and maintain muscle, there is now an opportunity to define protein intake by amounts and types that optimize health more broadly across the lifespan. Future protein research priorities should include addressing gaps in knowledge on cardiometabolic health, frailty, and weight management, according to the new paper.

The article “Exploring Opportunities to Better Characterize the Effects of Dietary Protein on Health across the Lifespan,” appears in a recent issue of the peer-reviewed journal Advances in Nutrition. Although muscle health is undoubtedly important, moving from muscle to other associated or disease-specific outcomes is a critical next step for the field, given the mounting evidence documenting the effects of dietary protein on measures of chronic disease and age-related decline such as cardiovascular disease, type 2 diabetes mellitus, obesity, frailty, and osteoporosis. 

The authors find that frailty research in particular could be improved as well by advancing “outcome” measures. Assessing frailty on a continuum, using validated measures, will allow scientists to identify intervention points in older adults who present with indicators of vulnerability despite no obvious signs of functional limitation. 

Along these lines, it will be valuable to begin incorporating various measures of mobility assessment, including self-reporting, laboratory-based metrics, and real-life measures from wearable devices. The integration of these three means of measuring mobility can provide a much more complete picture of how dietary protein, activity, or a combination of interventions affects a person’s functionality. 

Closely related is new science studying bone health. Recent advances in bone biology reveal novel roles for dietary protein in the pursuit of lifelong bone health. For example, there is mounting evidence that the skeleton is an endocrine organ unto itself, regulating other organs throughout the body, including skeletal muscle. High-resolution imaging technology holds promise to reveal the magnitude and mechanical consequences of dietary protein-derived benefits to bone.

Demonstrating cause and effect between any intervention, including dietary protein intake and bone health, lies in measuring actual changes in the bone tissue. The new article provides a “roadmap” for future research on the variety of health conditions in addition to frailty and bone health that protein affects. And that roadmap could affect the types of health claims that companies can make about their products.

New Science for New Health Claims

The U.S. Food & Drug Administration recently allowed a new qualified health claim for live dietary microbes in yogurt. In March 2024, the FDA authorized two options for statements on labels:

• “Eating yogurt regularly, at least 2 cups (3 servings) per week, may reduce the risk of type 2 diabetes. FDA has concluded that there is limited information supporting this claim."
• “Eating yogurt regularly, at least 2 cups (3 servings) per week, may reduce the risk of type 2 diabetes according to limited scientific evidence.”

When more knowledge gaps on protein are addressed, the FDA could be approached with scientific evidence to consider health claims for protein that could be used on food labels.

The recommended dietary allowance (RDA) for protein is 0.8 grams per kilogram body weight per day. The authors encourage research on how establishing optimal, rather than just minimal, protein intakes may affect a variety of health outcomes. This may logically lead to new science that can be marshalled for new health messaging claims for protein products given their potential for positive impacts on a variety of health conditions throughout life. For example, altering dietary protein quantity, quality, and source—that is, amino acids, isolated protein, protein-rich foods, or protein in mixed meals—may modulate insulin sensitivity, cardiovascular disease, frailty, osteoporosis and fracture risk, appetite, and obesity.

Protein across the lifespan

The article concludes that “As the field shifts emphasis to elucidating the role of dietary protein in supporting and sustaining human health throughout the lifespan, past research accomplishments provide a foundation for innovative thinking and an approach for the continued creation of an evidence base to best support future public health policy guidance and nutrition initiatives.”

And according to author John Carbone with Eastern Michigan University in a separate interview, “The advances the field has made over the last few decades in understanding how dietary protein affects muscle health have been remarkable. With this paper, we make the case for building off of these past accomplishments and encourage investigations of protein's role in modulating important outcomes that affect health across the lifespan. We begin by emphasizing cardiometabolic health, frailty prevention, bone health, and weight management, but believe this is just the beginning of expanding our understanding of how protein intake can be optimized to benefit quality of life for all."