Do you need to add carbs to protein to maximize muscle growth?

Insulin is the hormone that is released after eating. Carbohydrates have the reputation to stimulate insulin release, but protein can also increases insulin concentrations.

Insulin helps to get nutrients into the cells. Therefore, it could be speculated that insulin helps amino acids (the building blocks of protein) to get into the muscle.

This study investigated the effect of adding carbs to protein (to further increase insulin levels) on muscle protein synthesis and breakdown (the processes regulating muscle mass). Participants got 25 g whey protein on one test day, and 25 g whey protein plus 50 g carbs on the other test day.

As expected, insulin concentrations were much higher when protein and carbohydrates were combined. However, there was no difference in muscle protein synthesis or breakdown between the treatments.

Thus, 25 g protein appears to be sufficient to maximize the anabolic response of a meal. You don’t need to ingest extra carbohydrates and insulin levels do not need to be ‘spiked’.

However, keep in mind that muscle protein synthesis rates are still responsive to a prolonged energy deficit. If you eat to little calories for a couple of days, muscle protein synthesis rates will go down. Therefore, in practice you’ll still likely eat carbohydrates and/or fat with your protein.

In conclusion, adding carbs to protein does not further increase muscle protein synthesis and does not further inhibit muscle protein breakdown rates.

Study:

Staples et al. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Med Sci Sports Exe 2011.

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