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Front. Nutr. | doi: 10.3389/fnut.2019.00137

Commentary: Greek Yogurt and 12 Weeks of Exercise Training on Strength, Muscle Thickness and Body Composition in Lean, Untrained, University-Aged Males

  • 1Umeå University, Sweden

A commentary on
Greek Yogurt and 12 Weeks of Exercise Training on Strength, Muscle Thickness and Body Composition in Lean, Untrained, University-Aged Males. By Bridge A, Brown J, Snider H, Nasato M, Ward WE, Roy BD and Josse AR. Front. Nutr. 6:55. doi:10.3389/fnut.2019.00055

With great interest, I read the article by Bridge et. al. (1). Following a discussion on resistance training and dairy protein, the authors studied the effect of Greek Yogurt (GY) consumption in combination with 12 weeks of resistance training on strength, muscle thickness and body composition in lean, untrained, university-aged males. This commentary intends to constructively comment on the recently published article by Bridge et. al. by discussing some of the results, conclusions and the study design.

The authors are discussing the potential of GY as a post-exercise food, due to its high protein content. The protein in GY is mostly casein, which is discussed as a protein with unique characteristics because it can prolong plasma-amino acids and enhance whole-body protein turnover due to its slow absorption (2) and thus, allowing a net positive protein balance over a prolonged period time (3). Given the effectiveness of milk in the context of stimulating muscle protein synthesis (MPS) (4, 5) and health-related benefits of yogurt consumption (6-9) it is discussed that further studies on GY are warranted.

2 Discussion
One aim of the paper was to assess if GY could be used as a whole food source of protein to support training adaptations versus an iso-energetic control. The authors accurately address this question but become quite speculative on the beneficial effects of GY. In the introduction, the authors raised an interesting question: Would other dairy products elicit the same positive adaptations to resistance training as milk? However, this study compared GY to a carbohydrate-based pudding with no protein. One group consumed 200 g of GY (110 kcal, 20 g protein, 8 g carbohydrates) 3 times/day on training days, and 150 g of GY 2 times/day on non-training days. The control group consumed an iso-energetic, semi-solid carbohydrate-based chocolate-flavored placebo pudding (110 kcal, 0 g protein, 28 g carbohydrates).

Because the GY group received an additional 60 g of protein on training days, and 40 g on non-training days, their protein consumption (1.74g/kg/d) was significantly higher than the control group’s (1.22g/kg/d). It is evident that an increase in protein consumption of this magnitude will increase the adaptations and muscle hypertrophy by resistance training, as shown by several studies (10-14) and extensive meta-analyses (15-17). Participants in the GY group also consumed GY before bed, which most likely resulted in a decrease in muscle protein breakdown overnight (10).

Thus, the result are expected and leaves us with the question of whether other dairy products could elicit the same positive adaptations to resistance training as milk. While the study had several strengths, such as minimal inter-tester variation, and blinded trainers, as a result of the study design, it can only be concluded that a higher protein consumption, induced by 40-60 g of protein derived from GY per day, will increase the strength and muscle thickness in untrained males in combination with resistance training during 12 weeks. Thus, high-protein bacteria fermented milk, in addition to whole-milk and milk protein concentrates such as whey, is also able to potentiate adaptations from resistance exercise.
The study contributes to the literature of GY and protein supplementation and GY could be considered as a viable post-exercise food. However, while not the primary aim of the study, it would have been of great value to include a group consuming just milk, or whey protein, to answer the question regarding the effectiveness of other dairies in addition to milk. With equivalent protein intake across groups, a comparison of different protein sources is enabled. Thus, reducing the effects of a discrepancy in daily protein intake which will alter the adaptation to resistance training (16). The well-read authors discuss these matters and compares the present study with similar chronic training studies. One could interpret the findings and results as similar to prior studies with milk or whey supplementation, but this is only speculative. Still, the limitations of the study remain, and the authors make some unsubstantiated claims on the beneficial effects of GY. Such as GY could be more beneficial at promoting a positive protein balance than milk.

Nevertheless, the authors state an interesting question. Therefore, further studies analyzing consumption of GY, including measurements of plasma amino acids concentrations and calculations of muscle protein synthesis, briefly mentioned by the authors, are of interest to further shed light in the context of GY consumption in combination with resistance training. By using stable isotope methods, researchers could decipher the anabolic potency of GY on the stimulation of MPS enabling more in-depth comparison of GY versus other protein sources, and the potential of a whole-foods matrix on positively influencing the utilization of amino-acids by muscle tissue (18).

Keywords: Greek yogurt, Resistance Training, strength training, Exercise, PROTEIN INTAKE

Received: 30 May 2019; Accepted: 13 Aug 2019.

Copyright: © 2019 Jakobsson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Johan Jakobsson, Umeå University, Umeå, Sweden, johan.jakobsson@umu.se