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Overdoing Protein: When More Isn’t Better

Updated: Jan 28

Protein is an important component of an athlete’s diet. But as with all nutrients, there seems to be a ceiling to its benefits.


Introduction

We are taught that eating protein makes us big and strong. While there’s some truth to this statement, it lacks context. First of all, if you’re eating tons of protein but not doing any exercise, I hate to break it to you, but you’re not going to gain muscle mass or strength. Secondly, if it is true that protein does help us gain muscle and strength—provided that we do the gym work required—does this mean that the more protein we eat, the better?


If you have read our previous article on protein, you’ll be aware that there is a consensus in the field that eating about 1.6 grams of protein for every kilogram of our body weight per day (g/kg/d) seems to be the ‘sweet spot’ for supporting muscle and strength gains. However, a new study has put this to the test, to see if more protein is indeed better for performance gains.


Protein and performance.

For more on protein, see our previous article on the topic.


Why Protein is Important

Before we get into the study, let’s briefly talk about why protein is important for athletes. In simple terms, protein is the building block of body tissues like muscle. When we eat protein, we stimulate a process called muscle protein synthesis (MPS), which tells our body to make more proteins (and thus, muscle tissue). But again, the question becomes whether there’s a ceiling to its benefits (or not), which is what a recent study tested.


The Study

This study included 48 young, healthy, resistance-trained males, with an average age of 26 years (1). Each participant was randomised to either consume 1.6 g/kg/d or 3.2 g/kg/d of protein, alongside either a resistance training programme or a concurrent training programme (i.e., resistance training + aerobic training, or ‘cardio’). So in total, there were four groups:

  1. Resistance training + 1.6 g/kg/d of protein

  2. Resistance training + 3.2 g/kg/d of protein

  3. Concurrent training + 1.6 g/kg/d of protein

  4. Concurrent training + 3.2 g/kg/d of protein


Then, after 16 weeks of eating and training this way, differences in body composition (e.g., lean mass, fat mass), muscular strength and endurance (i.e., chest press, leg press), aerobic fitness (i.e., VO2max), and other measures of performance (i.e., vertical jump height, number of pull-ups performed) were assessed.


Protein shake athletes.

About one in four athletes use protein powders (2).


Results

There were few differences between groups for any of the outcomes: all groups gained about 2 kg of lean mass, a similar amount of muscular strength and endurance, and improved similarly in other measures of performance. However, there was a slight improvement in power for the higher protein (3.2 g/kg/d), resistance training group relative to the lower protein (1.6 g/kg/d), resistance training group. But this was a very small improvement (i.e., +0.1%). Naturally, the two concurrent training groups improved their aerobic capacity, whereas the resistance training groups didn’t. This makes sense: if you do ‘cardio’, you’re going to get fitter than if you don’t.


Takeaways

This study supports the established consensus that 1.6 g/kg/d is the ‘sweet spot’ for making muscle and strength gains (3,4). While there was a very slight improvement in power for the higher protein, resistance training group (relative to the lower protein comparator group), this single significant change, when contrasted to the relative equivalence for all other outcomes, is not enough to warrant a shift in protein recommendations. Further, very high protein intakes can sacrifice carbohydrate intakes, which is unwise as carbohydrates are the most important nutrient for fuelling optimal exercise performance (for most activities).


Bananas.

Bananas are a good source of carbohydrates and are a handy post-exercise snack.


Summary

Taking all of the available literature together, my advice would be to eat 1.6 g/kg/d of protein, and allow the rest of your diet to be made up of carbohydrates (first and foremost) and healthful sources of fats (e.g., nuts, seeds, liquid oils).


If you would like supplemental football training to improve your skills, reach out to our team of expert coaches at [email protected] to get started. And if you enjoyed this article, sign up to our mailing list to stay up to date.


Thank you for reading and have a great weekend!


Patrick Elliott, BSc, MPH

Health and Nutrition Science Communication Officer at Training121


References

(1) Bagheri R, Kargarfard M, Sadeghi R, Scott D, Camera DM. Effects of 16 weeks of two different high-protein diets with either resistance or concurrent training on body composition, muscular strength and performance, and markers of liver and kidney function in resistance-trained males. J Int Soc Sports Nutr. 2023;20(1):2236053. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10388821/


(2) Knapik JJ, Steelman RA, Hoedebecke SS, Austin KG, Farina EK, Lieberman HR. Prevalence of Dietary Supplement Use by Athletes: Systematic Review and Meta-Analysis. Sports Med. 2016 Jan;46(1):103–23. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4697915/


(3) Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, Aragon AA, Devries MC, Banfield L, Krieger JW, Phillips SM. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar;52(6):376–84. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867436/


(4) Nunes EA, Colenso-Semple L, McKellar SR, et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. J Cachexia Sarcopenia Muscle. 2022;13(2):795–810. Available at: https://onlinelibrary.wiley.com/doi/epdf/10.1002/jcsm.12922


Technical Terms

Muscle Protein Synthesis (MPS): The process by which our bodies build new muscle proteins. This can be influenced by a range of factors, including: nutrition, sleep, and exercise intensity.


VO2max: This is the maximum rate of oxygen consumption possible (for a given individual) during physical exertion. It is measured as millilitre of oxygen consumed per kg of body weight per minute (mL O2/kg/min). Athletes (particularly endurance athletes) have a greater VO2max compared to untrained individuals.

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