Corn protein alone, or in blends, stimulates muscle protein synthesis comparable to milk protein, with or without...

Due to their lower essential amino acid contents, particularly leucine, plant-derived proteins are generally considered to have lower muscle anabolic capacity than animal-based proteins. Corn protein is unique in having a relatively high leucine content; however, its anabolic effects have not been examined in older adults, who exhibit reduced anabolic sensitivity.

We examined the effect of corn protein isolate, a pea and corn protein blend, milk protein isolate, or a non-protein low-energy placebo on muscle protein synthesis (MPS), with or without resistance exercise, in older adults.

In a double-blind, placebo-controlled, randomized parallel group trial, 48 healthy older adults (68 ± 5 years; 24 males and 24 females) underwent a primed continuous infusion of L-[ring-¹³C₆] phenylalanine to estimate MPS using the precursor-product approach. Each participant performed unilateral knee extension exercise (3 sets of 10 repetitions at 75% of one-repetition maximum) and consumed 20 g of either corn protein (CORN), a pea and corn protein blend (PEA+CORN), milk protein (MILK), or a non-protein low-energy placebo (PLA). Blood and muscle samples were collected throughout.

The increase in MPS relative to basal values was greater in CORN (216 ± 170%; P < 0.001), PEA+CORN (217 ± 167%; P = 0.001), and MILK (138 ± 78%; P = 0.033) compared with PLA (77 ± 46%), with no differences between groups. Resistance exercise further increased MPS compared with supplementation alone in all groups (all, P < 0.001).

Ingestion of 20 g corn protein, a pea and corn protein blend, or milk protein increased MPS rates in healthy older adults, and resistance exercise further enhanced the anabolic response. This trial was registered at clinicaltrials.gov as NCT05917223.