Supplement Research - Does Insulin Reduce Muscle Tissue Breakdown?

By Robbie Durand, M.A.

Senior Science Editor

            In recent months, there has been much confusion about how many carbohydrates to use, post-workout. In Fakhri Mubarak’s last training video on musculardevelopment.com, he had an unusual-looking container so I asked, “What the hell is in there?” Fak replied, “Ah shit, it’s just Kool-Aid!” After laughing, he explained it was a mixture of Vitargo/amino acids that he sipped during his workout. So there is no doubt that during off-season, a good mixture of carbs and proteins is going to enhance muscle glycogen and boost performance in the gym. Anyone who has ever seen a glycogen-depleted bodybuilder knows that they hit the wall pretty fast, and training intensity goes to shit.

            In the past, carbs were known to enhance protein synthesis because of the spike in insulin, but that changed a few months ago when a study reported that 20 grams of essential amino acids (equivalent to about 50 grams of intact high-quality protein), or 90 or 30 grams of carbohydrates, all had similar effects on post-exercise protein synthesis. In that study, insulin was higher after ingesting 90 grams of carbohydrates, yet protein synthesis was still the same. So what about reducing muscle tissue breakdown? That’s exactly what the researchers wanted to find out, as reported in this month’s Medicine in Sports and Science and Exercise.

            In the above study, researchers had subjects complete a resistance training protocol, then consume one of two drinks. One drink consisted of 25 grams of whey protein isolate, while the other drink consisted of 25 grams of the same whey protein isolate and 50 grams of maltodextrin carbohydrate. The researchers found that the addition of carbohydrates did not impact muscle tissue breakdown, as there was no difference between the whey protein and whey protein plus carbohydrates group. The researchers suggested that the insulin spike induced by whey protein was sufficient to increase the maximal increase in protein synthesis rates, in addition to inhibiting muscle tissue breakdown.

            Before you throw out your maltrodextrins… WAIT!  The researchers did find that the addition of carbohydrates and whey protein stimulated Akt greater than whey protein alone. What the hell is Akt, you ask? Akt is a signaling pathway is associated with significant muscle hypertrophy in chronic exercise. Previous studies have shown that a single session of muscular exercise causes a transient increase in activation of the Akt/mTOR signal pathway within working muscles. Conversely, research demonstrates that IGF-1 activates the Akt pathway in chronic models of resistance overload. Based on findings that the combination of whey and carbohydrates increases Akt greater than whey alone, it could be hypothesized that the long-term use of carbs could chronically augment muscle hypertrophy. So although acutely, the roles of carbohydrates do not seem to enhance muscle protein synthesis or breakdown, chronically we still don’t know whether the addition of carbs will affect muscle hypertrophy.

Reference:

            Staples AW, Burd NA, West DW, Currie KD, Atherton PJ, Moore DR, Rennie MJ, Macdonald MJ, Baker SK, Phillips SM. Carbohydrate Does Not Augment Exercise-Induced Protein Accretion versus Protein Alone. Med Sci Sports Exerc, 2010 Dec 1.