Towel off from your workout, drink a protein shake. For exercisers trying to build lean, metabolism-revving muscle, it’s a no brainer.
But new research published in the June issue of Medicine Science in Sport Exercise suggests that your post-workout smoothie might not be quite as muscle-boosting as billed.
For the study, researchers at the University of Texas Medical Branch examined muscle growth in 54 healthy young men following a three-day-per-week resistance-training plan for 12 weeks. Following their workouts, one third of the guys drank a soy-dairy protein shake. Another third drank a whey protein isolate shake. Both types of shakes contained 22 grams of protein. Meanwhile, the final third of participants followed their workouts with a placebo shake. Zero protein there.
At the end of the study, researchers found that the guys who pounded post-workout protein didn’t build any more thigh muscle than those who went protein-free, explains Christopher S. Fry, PhD, assistant professor of nutrition and metabolism at the University of Texas Medical Branch. However, they did build slightly more total-body lean mass. Lean mass refers to everything that isn’t fat, but the researchers didn’t ID what exactly the extra mass was. It could have been muscle…it could have been something else.
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The Fine Print on Post-Workout Protein
At this point, you might be a) rejoicing at that you can now spend your protein-shake budget on something else or b) mourning all of those calories consumed in vain.
Either way, the study’s results aren’t as simple as “post-workout protein’s a sham.” Multiple studies, including some from this same research team, have shown that protein consumption following resistance exercise can increase muscle protein synthesis, or the integration of amino acids into muscle fibers. This is the process that makes muscles bigger and stronger.
Meanwhile, as Donald K. Layman, PhD, professor emeritus of food science and human nutrition at the University of Illinois, notes, there’s no way of knowing if the guys who downed the protein-free shake weren’t consuming post-workout protein from other sources. Whether that happened immediately following their workout or even several hours after, doesn’t matter either.
After all, both Fry and Layman note that the “anabolic window” may actually be much wider than previously thought. A 2014 review out of the UK even argues that muscle cells remain sensitive to protein intake up to 24 hours following resistance exercise.
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More Protein Than Published?
Plus, in the current study, all of the guys studied were already eating roughly 1.3 grams of protein per kilogram body mass per day. That’s even before figuring in post-workout protein supplementation. (So, for a 180-pound person, that would work out to 106 grams of protein per day.) The current recommended daily allowance for protein is 0.8 grams per kilogram body mass, which is much more in line with what the average adult eats per day, but current research is revealing that’s often inadequate for muscle health.
“These subjects may have already gotten all of the protein they needed for maximal muscle growth in tandem with resistance training, and anything on top of that wasn’t going to make a difference,” Layman says.
“Still, if this study was on 45-year-old rather than 20-something men, I’m not sure we would have seen the same results,” he continues. “The extra protein might have made a significant difference on muscle growth.” He explains that, post-30, hormonal changes make muscle cells progressively less responsive to protein ingestion. Basically, the older you get, the more protein you need to reap the same muscle-building gains. People who are cutting calories also tend to need more protein intake. It takes them longer to retain, let alone build muscle, compared with others.
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Your Best Protein Strategy
Overall, the take-home of the study is that, as long as you are eating enough protein, it probably doesn’t matter if you get it right after your workout in the form of protein powder or later in the day through whole foods such as meat, dairy and soy.
As for how much protein you need? Well, that’s still up for debate. Current research suggests that it’s more than the RDA of 0.8 grams per kilogram body mass. Some experts say the ideal range is actually 1.2 to 1.7 grams per kilogram bodyweight. And the study finds that sweet spot of 1.3 grams still seems to do the body some major good.