Optimal Protein Intake for Strength and Size
The New York Times reported yesterday on an interesting research paper published in the British Journal of Sports Medicine1. This meta-analysis looked at the effects of protein supplementation on muscle mass and strength increases in individuals engaged in a resistance training program.
Does supplementing with protein provide additional benefits over resistance training alone?
The research highlights the likelihood that the current RDA (Recommended Dietary Allowance) for protein is inadequate if you are resistance training to build muscle and get stronger. The authors also suggest that increased protein intake whilst engaging in resistance training is particularly important for those over the age of 40.
Let’s take a closer look at the research:
To be included in this meta-analysis the original experiments had to meet the following criteria:
- Last a minimum of 6 weeks
- Subjects performed resistance training at least 2x per week
- Subjects’ protein intake was tracked
- Protein supplementation was free of other known hypertrophic agents (e.g. creatine etc.)
- Changes in muscle size and strength were measured
- A control group was used.
The research methodology
The researchers found 49 existing papers that met all their requirements, yielding a total of 1,863 people studied, including:
- All ages, from young adults through to seniors
- Men and women
- Those with resistance training experience and novices.
How much protein did the research participants consume on average?
- The mean baseline protein intake of the participants across the included studies was ~1.4g protein/kg/day.
- The average supplemental amount of protein given to selected participants was ~35g protein/day.
The meta-analysis found that whilst engaged in a resistance training program:
- Subjects who consumed supplemental protein gained more strength and size than those who did not
- Extra protein was particularly important for those over the age of 40.
- Any form of protein appeared to be effective (whey, casein, soy, pea, milk, whole-food sources and protein blends were all used in the research studied).
- Timing and size of any postexercise dose of supplemental protein seems to be of minor importance, perhaps irrelevant.
- A total intake of ~1.6g protein/kg/day appears optimal for healthy adults, men and women. The confidence interval of this estimate is 1.03-2.20g protein/kg/day (it is 95% likely that the true mean of the population will fall in this range).
How does this protein intake tally with the current recommended dietary allowance for protein?
The current US/Canadian recommended dietary allowance (RDA) is 0.8g protein/kg/day. It therefore appears that the current US/Canadian RDA for dietary protein is inadequate for individuals engaged in resistance training who wish to optimise muscle mass and strength gain.
In our nutrition module (in the Master Personal Trainer and Personal Trainer courses), we’ve been recommending consuming 1.2-2g of protein/kg/day, which matches the confidence interval of this meta-analysis almost exactly. It’s great to see that there is additional research supporting our recommendation.
In addition, the researchers speculate that:
- Protein supplementation may be even more important for experienced trainees than novices when increasing muscle mass is a goal.
- Recommending the upper limit of the confidence interval (~2.2g protein/kg/day) to individuals who are focused on maximising resistance training induced gains in muscle tissue, may be prudent.
- If you perform resistance training with the goal of increasing strength and fat free mass and you are consuming less than 1.6g protein/kg/day then supplemental protein may be required to optimise your results.
- A person weighing 70kg would need to eat 3 typical-size chicken breasts to meet their daily protein requirement.
Questions arising from the research
- Is the elevated protein intake still required to maintain muscle mass, particularly if you pause resistance training for a period of weeks or months?
- In chronic resistance training where no more muscle tissue increase is possible for the individual, should protein intake be altered?
1 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 July 2017British Journal of Sports Medicine DOI10.1136/bjsports-2017-097608 Robert W Morton Kevin T Murphy Sean R McKellar Stuart M Phillips et al.
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