Writing in Sports Medicine – Open, the researcher from Meiji and Waseda University added that protein intake must be coupled with resistance training to see a significant improvement in muscle strength.
This is said to be the first time that a dose-response was found between protein intake and muscle strength.
“Previous studies have clarified the detailed relationship between muscle mass and protein intake, but in this study, we focused on muscle strength, which is the force exerted by muscles,” the company said.
Muscle strength is closely related to athletic ability, daily movement, and prevention of falls, while muscle mass is related to the activation of various chemical reactions throughout the body, such as basal metabolism, and the reduction of the risk of metabolic syndrome.
“Increased muscle strength leads to improved athletic performance and a lower risk of falls, and many studies have reported that people with strong muscle strength have a lower risk of developing cardiovascular disease, cancer, and even death in the future.
“While increasing one or the other alone has health benefits, we believe that a combination of sufficient protein intake and training can lead to a healthier body.”
Eighty-two research papers found on the databases PubMed and Ichushi-Web – an online academic article repository in Japan – were included in this meta-analysis.
These papers talked about randomised controlled trials (RCTs) investigating the effects of protein intake on muscle strength.
With the findings, the researchers created a forest plot to find out the effects of protein intake on muscle strength percentage changes.
They also created spline models to examine the correlation between total protein intake and muscle strength percentage changes from baseline.
Increased protein intake leads to a significant improvement in muscle strength only when combined with resistance training, the researchers reported.
“The percentage change in muscle strength gradually increased with total protein intake and peaked at approximately 1.5 g/kg body weight/day with resistance training.
“Muscle strength with resistance training increased by 0.72 per cent per 0.1 g/kg BW/d increase in protein intake up to 1.5 g/kg body weight/day, but no further gains were observed thereafter,” the researchers reported.
Without resistance training, they noticed that there was only a fractional increase in muscle strength, which increased slightly with total protein intake up to 1.3 g/kg body weight/day and gradually vanished after that.
In addition, results from the spline model showed that 1.5 g/kg body weight/day total protein intake with resistance training is required, in order to achieve the optimal effect on muscle strength.
At the same time, the researchers highlighted that certain groups of individuals should exercise caution when increased their protein intake.
“Although the beneficial role of protein intake in maintaining and enhancing muscle strength is well documented, the potential adverse effects of excess protein intake also need to be considered.
“High protein intake during pregnancy has been reported to increase the risk of small-for-gestational-age births and neonatal death,” they said.
Source: Sports Medicine – Open
Synergistic Effect of Increased Total Protein Intake and Strength Training on Muscle Strength: A Dose-Response Meta-analysis of Randomized Controlled Trials
Authors: Tagawa, R., Watanabe, D., Ito, K. et al.