Consuming carbohydrates after working out has long been over emphasized for its necessity to shuttle protein into your muscle. When ample protein has been ingested, carbs do not in fact have any additive effect on protein balance – the operative term here being “ample”. This is not to say you should avoid carbs but adding forms of sugar to your post workout protein shakes is, well, just like adding sugar to any meal and in some instances, much worse.
Conventional bro science wisdom is that carbs increase your insulin levels, which helps shuttle protein into your muscles. Translated into statistical terms, this means there is a positive interaction effect between protein and carbs on net protein synthesis. However, this widely held hypothesis is not supported by any research and explicitly falsified by many so-called pundits, i.e. Miller et al. and Staples et al. As with many theories in the fitness industry, it sounds plausible, but the empirical evidence demonstrates it is wrong.
So how come the myth you need carbs in your shakes is so prevalent?
- Supplement companies want you to believe you need carbs, because carbs are extremely cheap to manufacture. For example, basically all ”˜weight gainer’ products are just sugar sold at a ridiculous price.
- Many people read the carb-only research without realizing that protein makes the carbs redundant.
- Many myths perpetuate themselves, with everyone spreading the word simply because everyone else is also spreading the word. *insert sound of bleating sheep here*
They examined the differences in protein balance in groups consuming either 0, 0.15, or 0.6 g of carbs per kg of body weight when coingested with ~25g protein after resistance training. Their results? “Whole body protein breakdown, synthesis, and oxidation rates, as well as whole body protein balance, did not differ between experiments. […] In conclusion, co-ingestion of carbohydrate during recovery does not further stimulate post exercise muscle protein synthesis when ample protein is ingested.”
Staples et al. (2011) (https://www.ncbi.nlm.nih.gov/pubmed/21131864) wanted to replicate the above finding to end the discussion once and for all. After a weight training session, they gave their subjects either 25g of whey or both 25g of whey in combination with 50g of maltodextrin. They found that consuming 50g of maltodextrin along with 25g of whey does not stimulate muscle protein synthesis or inhibit protein breakdown more than 25g of whey alone.