|I still believe that the ill effects of fasting on skeletal muscle are way overrated, but I guess it won't hurt if you would be able to minimize it by sipping 60g of protein, right? A new study says: That's right, but there's more to it.|
This is however, only partly right. From previous articles here at the SuppVersity you know that studies investigating the effects of protein supplements on muscle protein maintenance exist and that the effect is - due to increased wastefulness - less pronounced than you probably hoped for.
Rittig et al. are right though, when they criticize that these studies failed to "include comparisons to other conventional nutrients and did not assess specific effects on muscle protein kinetics and signaling events" (Rittig. 2016). Needless to say that the Danish researchers tried to fill this gap in our knowledge about the anti-catabolic effects of different proteins and designed a study to test (i) whether a leucine rich (~16% of total protein content) whey protein beverage is more anabolic in muscle under catabolic conditions compared with isocaloric carbohydrate, and isocaloric isonitrogenous soy protein with and without 3 g HMB enrichment and (ii) whether leucine-rich whey protein specifically affects regulators of protein-synthesis and breakdown in muscle.
|Figure 1: Study design and composition of the test drinks (Rittig. 2016).|
- a beverage containing carbohydrate (CHO)
- a beverage based on leucine-rich whey protein (LWH)
- a beverage based on soy protein (SOY)
- a beverage based on soy protein + 3 g HMB (HMB)
- NBphe improved in all groups but more so for LWH and HMB compared with SOY (One-way repeated measure ANOVA, p < 0.05),
- Raphe decreased for CHO, LWH, and SOY in the sipping period compared with the fasting period (p < 0.05) but without any differences between groups.
|Figure 3: Total energy expenditure during fast (baseline) and while sipping the beverages expressed in kcal of oxidized protein, glucose and lipids; %-ages indicate rel. difference to baseline (Rittig. 2016)|
Overall, it is thus clear that leucine-rich proteins like whey and/or its metabolite HMB can (a) help you preserve lean muscle mass while fasting and (b) will do this more effectively than soy or carbohydrates which are not useless, but at least less effective. In that it may be worth highlighting that simply adding HMB to soy protein can change that, even though it did not have the mTOR-increasing effects the scientists expected HMB to have. Practically speaking, this means that the study at hand confirms that HMB works, but does not provide an explanation for the mechanism by which "HMB exerts its anabolic effect in human muscle" (Rittig. 2016) - after all, the soy + HMB treatment triggered a sign. decrease in muscle breakdown, even though it was not more successful in boosting mTOR than both the soy and the likewise ineffective carbohydrate treatment and in spite of no significant difference in the expression of catabolic protein signals.
- Baptista, Igor L., et al. "Leucine and HMB differentially modulate proteasome system in skeletal muscle under different sarcopenic conditions." PloS one 8.10 (2013): e76752.
- Naito, Takako, Akiko Kuma, and Noboru Mizushima. "Differential contribution of insulin and amino acids to the mTORC1-autophagy pathway in the liver and muscle." Journal of Biological Chemistry 288.29 (2013): 21074-21081.
- Noh, Kyung Kyun, et al. "β–Hydroxy β–Methylbutyrate Improves Dexamethasone-Induced Muscle Atrophy by Modulating the Muscle Degradation Pathway in SD Rat." PloS one 9.7 (2014): e102947.
- Rittig, Nikolaj, et al. "Anabolic effects of leucine-rich whey protein, carbohydrate, and soy protein with and without β-hydroxy-β-methylbutyrate (HMB) during fasting-induced catabolism: A human randomized crossover trial." Clinical Nutrition (2016).