Oct 15, 2024Interpreting new research for optimal protein intake post-workout
With constant advancements in the study and application of sport nutrition taking place, new research findings are around every corner. As the level of competition rises for even the most elite athletes, the application of new research can help them gain a competitive edge.
New science out of Maastricht University by Trommelen et al. is aiming to evolve how athletes might fuel, shining a big light on debunking previous post-workout protein recommendations.
First, it’s essential to understand the reasons why protein post-workout is so beneficial. High intense training that elite athletes undergo often results in muscle breakdown, putting the athlete in a catabolic state, or negative net protein balance. To promote health and healing, an athlete ideally wants to be in an anabolic state where they have a positive net protein balance (meaning the rate of newly synthesized body proteins exceeds the breakdown of body protein). When athletes consume amino acids (the building blocks of proteins) the body in essence “turns on” the muscle-building machinery to facilitate muscle protein synthesis (MPS). Once the dietary amino acids that are consumed are used to build muscle, an excess ingested protein that is not being used is broken down through oxidation and ultimately excreted. As a result, ample research has been conducted to optimize the appropriate dosage, timing, and composition of ingested protein to promote MPS and minimize oxidation.
These recent findings conducted by Trommelen et al. have challenged the previously accepted understanding that 20-30g of protein post-workout, and every “3-4 hours”, is the upper limit proven to be effective in promoting MPS while keeping oxidative rates low. In the randomized double-blind placebo-controlled study, the anabolic response to ingestion of dietary proteins was compared over 0-4 hours, 4-12 hours, and 0-12 hours. Tested subjects (n=36) were recreationally active males aged 18-40 who underwent a 60-minute whole-body resistance workout using 4×10 sets/repetitions at 65-80% of their 1 rep max. After the workout, subjects consumed a beverage with either 0 grams, 25 grams, or 100 grams of milk protein. Blood samples and muscle biopsies were taken from subjects periodically to compare rates of protein movement and muscle building within the body over time.
Findings from the research revealed that the anabolic state of the muscles is actually dose-dependent on the dietary amino acids ingested. When the 100-gram protein drink was compared to the 25-gram drink, protein synthesis rates were 40% higher during the 4-12 hour period and 20% higher in the 0-4 hour period. Why was this? Plasma amino acid concentrations were higher in the 100-gram protein group. They weren’t just oxidized and excreted, like would traditionally have been expected if absorption was maximized at the accepted 20-30g ‘upper limit’. Instead, increased circulation of amino acids resulted in greater availability for the muscles to uptake, thus further increasing the positivity of total body protein balance.
These data show us that more protein ingested might just require more time to be properly digested and absorbed to reach its full effect. This suggests that there is no upper limit for the amount of protein ingested, and there is no time limit of absorption for amino acids to create an anabolic effect.
Does that mean all athletes immediately should start taking in 100 grams of protein post-workout though? Maybe not. While Trommelen’s research provided new findings to create new discussions, some limitations are worth mentioning. Since the subjects tested only focused on recreationally active males, generalizing this data to elite athletes, and women, becomes difficult. Elite athletes are training at high intensities for extended periods compared to subjects who exercised less than 3x/week and were not previously in strength training. The stress put on the body during training can create drastic changes in needs such as increased protein, carbohydrates, and recovery protocols. For athletes who have already adapted to their training stimuli, or are in a constant catabolic state, protein synthesis can happen differently than in subjects who are new to resistance training and have not adapted. Add in increased variability with women, who have different metabolic and hormonal needs that play a role in muscle building and it becomes harder to apply this research to such a niche population.
In conjunction, the frequency of feedings and the type of proteins utilized in this study could also create limitations for application. Milk protein is unique when compared to other proteins as it contains casein, a slower-digesting protein. Since a slower-digesting protein would need more time to be absorbed, it would make sense that the results of a study containing a casein protein would require more time to be absorbed. Since this study was not compared with a faster-absorbing protein, like whey protein isolate, we can’t definitively say protein type doesn’t play a role in absorption and utilization. Since the frequency of feeding can also play a role in nutrient absorption, a comparison of 25g protein every 4 hours for 12 hours versus one single bolus of 100g protein could have provided us with more information on the upper limit. Only looking at bolus feeds can further advance the challenges of application as frequent feedings (every 3-4 hours) are common to meet athlete’s needs and keep them metabolically active.
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This research has expanded the discussion on best practices for optimal protein intake post-workout. But as we look further into the research, we see that there is no “one size fits all” approach when it comes to protein intake. Recommendations for protein intake, especially post-workout, are influenced by a variety of factors. The body’s adaptation to training, the amount of muscle breakdown, gender, body weight, type of protein, and frequency of eating are all factors to consider when discussing optimal protein intake for building muscle. This research further supports the ever-expanding idea that nutrition is not black and white, and often requires individualization to meet one’s needs.
This is especially true when adding in other factors that elite athletes face, such as intense training periods, increased nutrient needs, and busy schedules that create even higher importance on individualization.
Written by an American Sports and Performance Dietitians Association Registered Dietitian (RD). To learn more about sports nutrition and ASPDA, go to www.sportsrd.org.
