Protein’s potential to extend the ‘healthspan’

A new study urges nutrition scientists to expand the scope of protein research beyond the realm of muscle maintenance and strength as we age, after identifying multiple health conditions affected by protein that are ripe for further inquiry.

The nutrition experts who authored the study laud the significant gains made in the understanding of dietary protein and muscle over the past 30 years, and encourage future studies that assess how optimising protein intakes across the lifespan could advance health and wellbeing. The Institute for the Advancement of Food and Nutrition Sciences (IAFNS) supported the study, as generating science and evidence to promote health and wellness is at the core of its mission.

Historically, measures of muscle protein synthesis have prompted recommendations for protein quality, quantity, source and timing of protein intakes to enhance muscle health in ageing populations.

For example, recommendations that promote equally distributing dietary protein intake across meals, how much protein to consume within each meal and after exercise were derived from past studies on intakes of free-form amino acids, protein-containing foods, or mixed meals. However, nutrition experts say this is a target-rich environment that warrants greater research on a variety of other health conditions that protein affects.

Refocus: beyond muscle

Instead of focusing on the consumption of minimum quantities of protein to maintain muscle, scientists can now define protein ingestion that optimises health more broadly across a lifespan. Future protein studies should include addressing gaps in knowledge on frailty, weight management and cardiometabolic health, among others, according to the paper.

The article appears in a recent issue of the peer-reviewed journal Advances in Nutrition and was supported by the IAFNS Protein Committee. While muscle maintenance and enhancement are key, shifting research priorities to other associated or disease-specific outcomes is an important step for refocusing the field, particularly given recent studies on the effects of dietary protein on endpoints such as cardiovascular disease, frailty, type 2 diabetes mellitus, osteoporosis and obesity.

There is significant current interest in protein consumption, especially as related to obesity. Protein intake increases satiety following a meal via enhanced secretion of appetite-regulating hormones, such as glucagon-like peptide-1. Specific amino acids (that is, leucine, lysine, threonine and tryptophan) may exert greater effects on appetite hormones than others.

The protein source, eg, whey, casein, soy or pea, may also affect satiety, suggesting a role for specific amino acids in the underlying appetite response. Some additional research shows that the food matrix matters too, with solid foods typically eliciting a greater satiety than even protein-rich beverages. Teasing out the cause and effect warrants further exploration given that multiple adverse health outcomes are linked to obesity.

The authors additionally suggest that frailty studies could advance outcome measures related to healthspan. Using a continuum to assess frailty, while benchmarking and using validated measures, will allow researchers and clinicians to intervene in the lives of older, perhaps more vulnerable, adults who have yet to develop obvious functional limitations.

In this area, it will be valuable to incorporate multiple measures of mobility assessment, including self-reports, laboratory-derived metrics and everyday-life measures from new wearable devices that capture real-time information. Integrating these modes of assessing mobility will provide a more comprehensive view of how dietary proteins, activity, or a combination of interventions, affect a patient’s functionality. The article provides a roadmap for future research on the variety of health conditions, in addition to frailty and bone health, that protein affects.

New science on healthspan

The authors say a broader focus on a variety of symptoms and health conditions could expand what is being called the ’healthspan’. The healthspan is defined as the amount of time a person spends in good health, free of chronic disease and disability. It is meant to be a measure of health and not just longevity.

The recommended dietary allowance (RDA) for protein is 0.8 grams per kilogram of 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 and extend the healthspan of populations. This may strengthen the potential for positive impacts through interventions on health conditions across life stages. For example, altering dietary protein quantity, quality and source – ie, amino acids, isolated protein, protein-rich foods, or protein in mixed meals – may positively impact insulin sensitivity, cardiovascular disease, appetite, obesity, osteoporosis and bone fracture risk.

Protein and expanding the healthspan

The authors of the article conclude 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.”

Advancing the science on dietary protein holds much promise for expanding the healthspan. By increasing our understanding of the role of protein and specific amino acids on cardiometabolic health, frailty prevention, bone health and weight management, protein intake can be optimised to benefit quality of life for all.