Recent investigations support the concept that when the amounts of high-quality protein, providing essential amino acid including leucine, reach a threshold, the effects on muscle protein synthesis and training adaptations seem to be similar regardless of the source (Reidy and Rasmussen, 2016). The recent published double-blind randomized controlled trial study of Sharp et al. analysed the effects of the four treatment conditions at maximizing training outcomes in trained men and women (Sharp et al., 2017). Participants were randomly allocated into the following 4 groups
• Whey protein concentrate (n=10, 5 males, and 5 females)
• Beef isolate (n=10, 5 males, and 5 females)
• Hydrolysed chicken protein (n=11, 5 males, and 6 females)
• Maltodextrin, non-protein contrast group (n=10, 4 males and 6 females
All participants performed an 8-week training protocol involving 3-resistance training and 2 low volume high-intensity interval cycling training per week. Supplements (46 g of product) were consumed immediately after workout and in a similar time during non-training days. Overall, the ingestion a post workout protein supplementation (representing between 0.76g to 0.54 g/kg) from Whey Concentrate, Beef isolate or Hydrolysed Chicken was effective to optimize body composition (increase Fat-free mass and decrease body fat) and strength gains compared to a contrast non-protein only carbohydrate group. Additionally, only the Whey protein group significantly increase power output in cycling (Wingate test). Furthermore, no significant gastrointestinal distress was reported by any of the participants. Authors support the use of protein supplementation in resistance training and indicate that provided a minimum amount of essential amino acid is consumed, the source of protein can be self-selected by the individual preference or special conditions, e.g. lactose intolerance, allergies, etc.
Even though the aforementioned study is in agreement with others (Naclerio et al., 2017a, Naclerio et al 2017b) there are some concerns that deserved our attention. The influence sex has not been properly explained. No control of the use of contraceptive in women was reported. Some forms of oral contraceptive have been shown to impact protein metabolism and may, therefore, influence changes in lean body mass and strength (Smith and Mittendorfer, 2016). In addition no indication about how the supplements have been consumed (mixing with water, juice, etc). Furthermore, in order to compare with others similar studies a detailed description of the nutritional composition of the 3 protein supplements (aminogram, vitamins, minerals, fatty acids, etc.) is needed. Although the source for manufacturing protein extract from milk, beef or chicken would be similar, there are still substantial differences in the nutritional composition of the commercialised supplement products depending on the manufacturing process and whether the proteins are extracted from muscles, cartilages, bones or blood. The aforementioned issues would seriously impact the observed results and specifically on the minimum amount of protein (threshold) needed to elicit the expected changes for each particular population.
NACLERIO, F., LARUMBE-ZABALA, E., ASHRAFI, N., SEIJO, M., NIELSEN, B., ALLGROVE, J. & EARNEST, C. P. 2017a. Effects of protein-carbohydrate supplementation on immunity and resistance training outcomes: a double-blind, randomized, controlled clinical trial. Eur J Appl Physiol, 117, 267-277.
NACLERIO, F., SEIJO, M., LARUMBE-ZABALA, E., & EARNEST, C. P. 2017b. Carbohydrates Alone or Mixing With Beef or Whey Protein Promote Similar Training Outcomes in Resistance Training Males: A Double Blind, Randomized Controlled Clinical Trial. Int J Sport Nutr Exerc Metab, in press.
REIDY, P. T. & RASMUSSEN, B. B. 2016. Role of Ingested Amino Acids and Protein in the Promotion of Resistance Exercise-Induced Muscle Protein Anabolism. J Nutr.
SHARP, M. H., LOWERY, R. P., SHIELDS, K. A., LANE, J. R., GRAY, J. L., PARTL, J. M., HAYES, D. W., WILSON, G. J., HOLLMER, C. A., MINIVICH, J. R. & WILSON, J. M. 2017. The Effects of Beef, Chicken, or Whey Protein Post-Workout on Body Composition and Muscle Performance. J Strength Cond Res.
SMITH, G. I. & MITTENDORFER, B. 2016. Sexual dimorphism in skeletal muscle protein turnover. J Appl Physiol (1985), 120, 674-82.