Whey before workout reduces cortisol level, soya protein doesn't
Some time ago we wrote that strength athletes build up more lean body mass if they consume whey rather than soya protein or fast carbohydrates just after a training session. The authors of that study also discovered that pre-training whey supplementation inhibits the increase in the stress hormone cortisol, and supplementation with soya protein or carbohydrates does not.
Cortisol is a useful, even essential hormone, but strength athletes who want to build up muscle mass would prefer to keep their post-workout levels down. Cortisol forces muscles to convert proteins into energy and also inhibits the effect of the androgen receptor, through which muscle cells receive important anabolic signals.
Researchers have long known that intensive exertion causes cortisol levels to rise, and that combining quickly absorbed nutrients such as simple carbohydrates with a high glycaemic index helps to reduce the rise. In the study we're referring to here, the researchers wanted to find out whether fast-absorbed proteins also have this effect.
The researchers got ten experienced young strength athletes to do six sets of squats using a weight that they could just manage ten reps with, on three different occasions. One time the men drank a shake containing 20 g of the easily absorbed carbohydrate maltodextrin [CHO], another time they drank a shake containing 19 g whey isolate [WPI], and the third time they drank a shake containing 18 g soya-protein isolate [SPI]. The athletes drank the shakes twenty minutes before starting their workout. The soya-protein shake also contained 26 mg isoflavones.
The figure below shows how the cortisol level in the men's blood rose after doing strength training. When the men had drunk the whey shake the increase was noticeably less than after drinking the soya-protein or maltodextrin shake.
The researchers also noticed that there was an effect on the men's testosterone level. This rose more after the men had drunk the whey shake than after the soya-protein shake.
The researchers interpret both the hormonal effects of whey as being positive, and suspect that strength athletes can recover faster from strength training by consuming a portion of whey just before a session.
J Am Coll Nutr. 2013;32(1):66-74.
Post-workout shake with 22g whey works better than one with 22g soya protein 20.12.2013
Rice protein works just as well as whey for bodybuilders 19.07.2013
Using whey during strength training helps tendons grow faster 04.07.2013
Nutrition & Strength Training