Protein2026-06

Association of handgrip strength with the plasma metabolomic profile: secondary analysis of a protein intervention study.

Martinsen Tilde, Wirth Janine, Brennan Lorraine — Metabolomics : Official journal of the Metabolomic Society

Summary

A study in older adults found that the type of protein consumed (plant vs. dairy) didn't significantly alter their blood metabolite profiles. However, certain blood markers, including amino acids like leucine, were associated with better handgrip strength and improvements in muscle function over time. This suggests that an individual's metabolic state might play a role in muscle health.

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Key points

Protein source (plant vs. dairy) did not change blood metabolite profiles in older adults.
Specific blood markers, like certain amino acids, were linked to handgrip strength.
Higher levels of some metabolites were associated with improvements in handgrip strength.
Assessing an individual's metabolic state might be important for muscle-focused interventions.

What the study looked at

Researchers wanted to understand if different protein sources, specifically plant-based versus dairy proteins, would affect the mix of small molecules (metabolites) in the blood of older adults. They also explored if these blood metabolites were connected to muscle strength, measured by handgrip. This study re-examined data from a 12-week clinical trial involving 171 healthy adults aged 50 and older. Participants had previously received daily supplements of either high plant protein, high dairy protein, or a low protein control. Blood samples were analyzed for various metabolites, and handgrip strength was measured. The study found that the *type* of protein supplement did not significantly change the overall blood metabolite profile. However, several specific blood metabolites, including amino acids like leucine and isoleucine, were strongly linked to an individual's handgrip strength. Some of these baseline metabolite levels were also associated with positive changes in handgrip strength over the study period.

Dietary takeaway

While this study didn't show that specific protein *types* directly alter blood metabolites in a way that impacts muscle strength, it highlights the importance of overall metabolic health. Adequate protein intake, regardless of source, is crucial for muscle maintenance, especially as we age. This research suggests that certain amino acids, abundant in protein-rich foods, are linked to muscle strength. Remember, this is one study, and more research is needed to draw definitive conclusions about specific dietary recommendations.

Abstract

INTRODUCTION: There is interest in the potential impact of increased protein intake on muscle function in older adults. However, there is paucity of information on effects of different protein types. OBJECTIVES: To determine the impact of protein sources (plant vs dairy) on the plasma metabolomic profile, and to explore associations between metabolites and handgrip strength. METHODS: In this secondary analysis of a 12-week double-blinded RCT, 171 healthy adults (≥50 years) were assigned to high plant protein (23 g/d), high dairy protein (22 g/d) or low protein (2 g/d) supplement. Plasma samples were collected pre- and post-intervention and analysed using a targeted LC-MS platform. Main and interaction effects were estimated using ANOVA-simultaneous component analysis (ASCA). Spearman correlation analysis evaluated associations between metabolites and handgrip strength, with false discovery rate correction (q < 0.05). RESULTS: ASCA revealed no significant main effect of group (p = 0.23) or group × time interaction (p = 1.00), while time had a significant effect on the metabolomic profile (p < 0.05). After FDR correction, 26 metabolites were significantly correlated with baseline handgrip strength. The strongest positive correlations were observed for creatinine (r = 0.53), leucine (r = 0.38), proline (r = 0.35) and isoleucine (r = 0.33). Baseline levels of leucine, isoleucine, PCaeC322 and SMOHC222 were associated with positive changes in handgrip strength (p < 0.05). CONCLUSIONS: Metabolomic changes were not related to protein type. However, metabolite levels were correlated with handgrip strength outcomes, suggesting the necessity to evaluate the metabolic state of individuals prior to interventions. TRIAL REGISTRATION: This study is registered on isrctn.com as ISRCTN16651067.

View on PubMed →DOI: 10.1007/s11306-026-02496-4