A robust and validating finding for anyone who prefers to consume a largely plant-based diet! :o)
A meta analysis recently published in the International Journal of Sports Nutrition and Exercise Metabolism has confirmed that supplementing a resistance training programme with soy protein provides equal gains in lean body mass as supplementing with animal-based proteins.
Previously, studies had shown that the higher levels of leucine (one of the 'essential' amino acids) in animal-derived proteins meant that they were more effective at stimulating muscle protein synthesis over the short term. However, there was little consensus as to whether these effects translated into longer term influences on body composition.
The authors of the present analysis therefore pooled data from 9 individual studies involving 266 participants, and used some fancy statistics to determine the underlying patterns.
(Yes, you guessed it, the exact details of how meta-analyses are conducted are beyond me! All I know is that by pooling data from multiple studies you increase the 'power' of the analysis, which is your probability of detecting what is really going on. Sometimes individual studies lack power to detect what is actually happening, simply because they are too small. Oh, and I also know that meta-analyses require some clever mathematicians and a very large computer!).
The results of the meta-analysis showed that supplementing a resistance exercise training programme with either soy, whey, or 'other' animal proteins all led to significant increases in lean body mass versus training alone, and that there was no significant difference between the types of supplement used. Unsurprisingly, supplementing with soy or whey protein in the absence of resistance training did not affect lean body mass.
I'd be interested to know from future studies how other plant-based proteins stack up against those studied here. Soy does have a reputation as being one of the few plant-based proteins that contains high enough levels of leucine to be considered 'complete'. Would quinoa and buckwheat (also considered 'complete' proteins) perform quite so well I wonder?
In the meantime, if tofu, veggie wieners and soy shakes are your protein of choice, you can rest easy in knowing your gains in lean body mass won't be affected. Xxx
Reference: Messina M, et al. Int J Sport Nutr Exerc Metab 2018; Epub ahead of print