Protein2026-10

Ingestion of 20 g of a Plant-derived Protein Blend With and Without Added Leucine or Whey Protein Does not Increase Muscle Protein Synthesis Rates in Older Males.

Kuin Lisa Me, Hermans Wesley Jh, Boot Noortje, Fuchs Cas J et al. — The Journal of nutrition

Summary

A study investigated if different 20-gram protein supplements could stimulate muscle building in older men. Researchers found that neither a plant-based protein blend, the same blend with added leucine, nor whey protein significantly increased muscle protein synthesis rates. This suggests that 20 grams of protein might not be enough to effectively stimulate muscle growth in older adults, regardless of its source or quality.

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Key points

20 grams of protein, whether plant-based or whey, did not stimulate muscle building in older men.
Adding leucine to plant protein also did not improve its effect on muscle protein synthesis in this group.
Older adults may require more than 20 grams of protein per meal to effectively support muscle health.

What the study looked at

What question the study asked: This study investigated whether consuming 20 grams of a plant-based protein blend, with or without added leucine, or whey protein, could stimulate muscle protein synthesis in older men. The aim was to see if plant protein could be made as effective as animal protein for muscle building in this age group. How it was studied (design/participants): Forty-five healthy older men, with an average age of 69, were randomly assigned to one of three groups. Each group consumed 20 grams of protein: either a blend of soy and pea protein, the same plant blend fortified with extra leucine, or whey protein. Researchers then measured their muscle protein synthesis rates over four hours after consumption. What it found: The study found that none of the 20-gram protein supplements—plant blend, plant blend with leucine, or whey protein—significantly increased muscle protein synthesis rates in these older men. This suggests that 20 grams of protein, regardless of its source or whether it's enhanced with leucine, might not be a sufficient amount to stimulate muscle building in older adults.

Dietary takeaway

For older adults aiming to maintain or build muscle, this study suggests that consuming just 20 grams of protein per meal might not be enough, even if it's high-quality whey or fortified plant protein. It highlights the potential importance of consuming larger amounts of protein at meals to effectively support muscle health. However, remember that this is just one study, and individual needs can vary, so it's not a definitive recommendation.

Abstract

BACKGROUND: Sufficient high-quality protein intake is required to prevent sarcopenia in older adults. Plant-based proteins have been reported to have lower anabolic properties when compared with animal-based proteins. Whether the lower quality of plant-based protein can be improved, thereby resulting in an anabolic response noninferior to an equivalent amount of animal-based protein, remains to be established in older adults. OBJECTIVES: To compare postprandial muscle protein synthesis rates following ingestion of a single bolus of a PLANT, with a PLANT+LEU, or WHEY in older males. METHODS: In this randomized, double-blind, parallel-group design, 45 healthy older males (aged 69 ± 5 y, BMI 26.2 ± 3.2 kg·m) were selected to ingest a 20 g protein blend combining 12 g soy plus 8 g pea protein soy- and pea-derived protein blend (PLANT), 20 g of the soy-pea protein blend fortified with 2 g leucine soy-pea protein blend fortified with free leucine (PLANT+LEU), or 20 g whey protein (WHEY). Primed continuous L-[ring-C]-phenylalanine infusions were applied, with blood and muscle sampling ≤4 h after protein ingestion to assess plasma amino acid profiles and muscle protein synthesis rates. RESULTS: WHEY increased plasma essential amino acid concentrations more than PLANT and PLANT+LEU over the 4 h postprandial period (incremental area under curve: 135 ± 20 compared with 99 ± 21 and 105 ± 21 mmol·240 min·L, respectively; P < 0.001). Plasma peak leucine concentrations were higher after PLANT+LEU ingestion compared with PLANT and WHEY (567 ± 74 compared with 310 ± 49 and 471 ± 74 μmol·L, respectively; P < 0.001). Postprandial muscle protein synthesis rates averaged 0.034 ± 0.010, 0.035 ± 0.012, and 0.034 ± 0.010 %·h following PLANT, PLANT+LEU, and WHEY ingestion, respectively (treatment P = 0.828), and were not increased when compared with postabsorptive values. CONCLUSIONS: Ingestion of 20 g of protein alone, independent of its quality, is not enough to increase muscle protein synthesis rates in older males. More work is needed to define the preferred combination of both protein quality and quantity to stimulate muscle protein synthesis in an older population. This trial was registered at clinicaltrials.gov as NCT05711095.

View on PubMed →DOI: 10.1016/j.tjnut.2026.101789