Plant-based proteins boost muscle mass and cut fat in older adults

A recent study published in the journal Nutrients describes the effects of plant-based protein interventions on physical function, body composition, and strengths in the older population, as well as whether exercise improved the efficacy of these interventions.

Study: Effects of Plant-Based Protein Interventions, with and without an Exercise Component, on Body Composition, Strength and Physical Function in Older Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Image Credit: Antonina Vlasova / Shutterstock.com

Background

Aging is associated with sarcopenia, which is the progressive loss of skeletal muscle mass, strength, and performance. The development of sarcopenia is associated with many health-related issues, including functional decline, higher risk of falls, loss of independence, and higher hospitalization rates.

A higher protein intake and regular physical activity are common strategies adopted to prevent sarcopenia. However, the effectiveness of these strategies depends upon the types, doses, and timing of implementation.

Plant-based proteins are potential alternatives to conventional animal-based proteins. Compared to animal protein sources, plant-based protein can be produced relatively easily and release significantly fewer greenhouse gases.

In contrast to animal-based foods, plant-based products are also rich in other dietary nutrients such as polyphenols, fiber, and unsaturated fats. Importantly, plant-based protein sources are less nutritionally effective than animal sources due to poor digestibility and incomplete amino acid profiles. However, these limitations have been overcome with the development of plant-based “mylks” and meat analogs, which exhibit improved digestibility and complete amino acid intakes.

Aging is associated with impaired protein metabolism due to changes in the digestion process, chronic inflammation, hormonal alterations, reduced muscle protein synthesis, anabolic resistance, and insulin resistance. Several studies have indicated that components of plant proteins, such as isoflavones in soy, have an inflammatory effect, which could ultimately prevent the development of sarcopenia. 

To date, most reviews have analyzed the effect of animal-based protein sources like whey on skeletal muscle development in younger and older populations. Thus, there remains a lack of systematic reviews related to the impact of plant proteins on sarcopenia.

About the study

The current systemic review assessed the effect of plant-based protein on physical function, body composition, and strength in older adults 60 years of age and older. All relevant articles published between 1947 and January 2023 were obtained from databases including Embase, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Medline.

The review considered all randomized controlled trials (RCT) that compared the effects of plant-based protein interventions with placebo treatment on body composition, strength, or physical function among adults 60 years of age and older. Non-English articles, animal studies, case-control studies, and non-RCT participants with cachexia or medical conditions that impacted metabolism were excluded from the analysis.

Study findings

A total of 8,068 articles were obtained from the initial search. After removing duplicates and matching studies with the eligibility criteria, thirteen studies were included in the review.

The consumption of plant proteins was associated with improved lean muscle mass accrual and strength over time. No significant difference was observed between plant-based protein interventions and control interventions, in which control interventions included animal protein, placebo (no interventions), exercise, and exercise + animal protein intervention.

This observation implies that the outcome of plant protein interventions was comparable to control interventions. Although plant-based protein interventions exhibit positive effects in older adults, more studies are needed to validate this finding.

The current study highlights that plant-based protein sources will benefit older adults with impaired anabolic metabolism. In addition to improving muscle mass, plant proteins also support fat mass loss, thereby demonstrating their positive effect on overall body composition.

Typically, an increase in fat mass has been linked with aging, as it contributes to insulin resistance, muscle mass decline, morbidity, and mortality risks. Therefore, an increase in plant protein intake would reduce fat mass in older adults.

Compared to control interventions, plant-based protein interventions prevent declining body strength and function in older adults. The vitamins, fibers, minerals, antioxidants, and antioxidants in plant proteins impact muscle health by decreasing inflammation and mitigating the adverse effects of reactive oxygen species on muscle tissue, ultimately improving muscle strength and function.

Notably, plant-based proteins were found to perform better without an exercise component.

Conclusions

The current systematic review summarizes the effectiveness of plant-based protein interventions for improving physical function, body composition, and strength in the older population. Improved lean muscle mass and a more significant reduction in fat mass were associated with plant-based intervention in older adults.

Since the current study only focused on soy protein sources, future studies are needed that include newer plant proteins, such as microalgae and peas, to assess their effect on the targeted older population.