Levels of leucine in whey protein found to have limited effect on post-exercise responses

24 Nov 2017 --- Despite higher-magnitude increases in blood leucine concentrations with native whey, it was not superior to regular whey (WPC-80) when it came to the effect on muscle protein synthesis and phosphorylation of the protein p70S6K during a five-hour post-exercise period. This is according to a study published in the Journal of the International Society of Sports Nutrition.

Native whey was also noted to increase phosphorylation of p70S6K and muscle protein synthesis rates to a greater extent than milk during the five-hour post-exercise period.

Study compares anabolic effects of protein types
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). The study compared the acute anabolic effects of ingesting 2 x 20g of native whey protein, WPC-80 or milk protein after a resistance exercise session.

A total of 24 young resistance trained men and women took part in the double-blind, randomized, partial crossover, controlled study. Participants received either WPC-80 and native whey – in a crossover design – or milk. Supplements were ingested immediately (20g) and two hours after (20g) 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 analyzed by a one-way analysis of variance (ANOVA) and comparisons between the whey supplements and milk were analyzed by a two-way ANOVA.

Native whey was found to increase blood leucine concentrations more than WPC-80 and milk. Native whey ingestion induced a greater phosphorylation of p70S6K than milk 180 minutes after exercise. Muscle protein synthesis rates increased one to three hours after exercise with WPC-80 (0.119 percent), and one to five hours after exercise with native whey (0.112 percent). Muscle protein synthesis rates were higher one to five hours after exercise with native whey than with milk.

Levels of leucine in whey protein are one of the hot topics in the sports nutrition space. The recent webinar “A Pouch for Olympic Gold,” hosted by NutritionInsight’s sister website FoodIngredientsFirst, discussed leucine’s role and had a strong focus on protein’s role in recovery and muscle-building benefits, even while sleeping.

“I think that [amino acids are] all important, but the only one that can trigger the onset of protein synthesis seems to be leucine,” said Professor Asker Jeukendrup, Performance Manager Nutrition at NOC*NSF Dutch High Performance Team and Owner at mysportscience sport science consulting services.

By Paul Creasy