Native whey protein with high levels of leucine results in similar post-exercise muscular anabolic responses as regular whey protein: a randomized controlled trial

Abstract

Background: Protein intake is essential to maximally stimulate muscle protein synthesis, and the amino acid leucine seems to possess a superior effect on muscle protein synthesis compared to other amino acids. Native whey has higher leucine content and thus a potentially greater anabolic effect on muscle than regular whey (WPC-80). This study compared the acute anabolic effects of ingesting 2 × 20 g of native whey protein, WPC-80 or milk protein after a resistance exercise session.

Methods: A total of 24 young resistance trained men and women took part in this double blind, randomized, partial crossover, controlled study. Participants received either WPC-80 and native whey (n = 10), in a crossover design, or milk (n = 12). Supplements were ingested immediately (20 g) and two hours after (20 g) a bout of heavy-load lower body resistance exercise. Blood samples and muscle biopsies were collected to measure plasma concentrations of amino acids by gas-chromatography mass spectrometry, muscle phosphorylation of p70S6K, 4E-BP1 and eEF-2 by immunoblotting, and mixed muscle protein synthesis by use of [2H5]phenylalanine-infusion, gas-chromatography mass spectrometry and isotope-ratio mass spectrometry. Being the main comparison, differences between native whey and WPC-80 were analysed by a one-way ANOVA and comparisons between the whey supplements and milk were analysed by a two-way ANOVA.

Results: Native whey increased blood leucine concentrations more than WPC-80 and milk (P < 0.05). Native whey ingestion induced a greater phosphorylation of p70S6K than milk 180 min after exercise (P = 0.03). Muscle protein synthesis rates increased 1-3 h hours after exercise with WPC-80 (0.119%), and 1-5 h after exercise with native whey (0.112%). Muscle protein synthesis rates were higher 1-5 h after exercise with native whey than with milk (0.112% vs. 0.064, P = 0.023).

Conclusions: Despite higher-magnitude increases in blood leucine concentrations with native whey, it was not superior to WPC-80 concerning effect on muscle protein synthesis and phosphorylation of p70S6K during a 5-h post-exercise period. Native whey increased phosphorylation of p70S6K and muscle protein synthesis rates to a greater extent than milk during the 5-h post exercise period.

Trial registration: This study was retrospectively registered at clinicaltrials.gov as NCT02968888.

Keywords: Amino acids; Nutrition; Protein quality; Resistance training; Skeletal muscle; Stable isotopes; Supplementation.

Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the Regional Ethics Committee for Medical and Health Research of South-East Norway (2014/834/REK sør-øst C) and performed in accordance with the Declaration of Helsinki. All participants signed a written informed consent form before entering the study.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Participant flowchart

Fig. 2

Experimental design

Fig. 3

Blood concentrations of essential amino acids (a), branched chain amino acids (b) and leucine (c) following intake of milk, WPC-80 or native whey immediately and two hours after a bout of heavy leg resistance exercise. Arrows indicate time points of protein supplement ingestion. Values are mean ± SD (only shown for highest and lowest values). n = 12 in the milk group and 10 in the WPC-80 and native whey group. Black symbols are significantly different from resting values. # native whey greater than milk at the same time point; $ WPC-80 greater than milk at the corresponding time point; & native whey greater than WPC-80 at the corresponding point, p < 0.05

Fig. 4

Blood concentrations of glucose (a), insulin (b), urea (c) and creatine kinase (d) following intake of 20 g milk protein, WPC-80 or native whey immediately after a bout of heavy leg resistance exercise. Arrows indicates time point of protein supplement ingestion. Values are mean ± SD (only shown for highest and lowest values). n = 12 in the milk group and 10 in the WPC-80 and native whey group. Black symbols are significantly different from resting values. # native whey greater than milk at the same time point; & native whey greater than WPC-80 at the same time point, p < 0.05

Fig. 5

Ratio between phosphorylated and total p70S6K (a), 4E–BP1 (b) and eEF-2 (c) following intake of milk, WPC-80 or native whey immediately and two hours after a bout of heavy leg resistance exercise. Values are mean ± SD. n = 12 in the milk group and 10 in the WPC-80 and native whey group. * Different from resting values. # different from milk at the corresponding time point, p < 0.05

Fig. 6

Mixed muscle FSR values following intake of milk, WPC-80 or native whey immediately and two hours after a bout of heavy leg resistance exercise. Values are mean ± SD. n = 10 in the milk group and 10 in the WPC-80 and native whey groups. # Different from milk over the corresponding time period, p < 0.05

Fig. 7

Isometric knee extensor force-generating capacity relative to resting values following intake of milk, WPC-80 or native whey immediately and two hours after a bout of heavy leg resistance exercise. Values are mean ± SD. Black symbols are significantly different from baseline, p