Will adding soy protein to your post-workout shake lead to improved strength gains? Findings from a recent study

For most women, adding resistance training to their fitness regime is the easiest way to reduce body fat and sculpt shapely muscles. Building muscle, however, requires protein, a dietary component that many simply aren’t getting enough of.

Not only does protein help to develop and strengthen muscle fibers, it also increases satiation, making it less likely that you’ll experience and give in to cravings for simple carbohydrates after your workout, thereby undermining your health and fitness goals.

I often recommend that my personal training clients consume protein shakes within an hour of their strength workouts; a simple way to get an extra serving of protein into their day. While many choose to supplement with whey or casein isolate powders, some have trouble digesting the milk-based proteins or, for other reasons, prefer to minimize the animal products in their diet.

Enter soy protein.

Like proteins derived from dairy and meat, soy protein contains the full complement of amino acids required by your body for all of its day-to-day functions. It’s low in fat and widely available. It contains more glutamine (a free radical-reducing antioxidant) and arginine (which speeds muscle recovery via improved blood flow) than either whey or casein. It has an intermediate digestion time (slower than whey and faster than casein), suggesting that when used in concert with one or both of the milk-based proteins, it may increase the length of the post-exercise recovery period during which muscle growth occurs. I’m all for getting the most out of my workouts!

At a recent academic conference, Dr. B. Rasmussen and colleagues (University of Texas, Medical Branch), presented the results of a preliminary study they conducted comparing the post-strength training benefits of consuming a soy/whey/casein protein mix relative to supplementing with whey alone.

Nineteen young adults (all male) were randomly assigned to one of the two treatments (whey and a combination of whey, casein and Solae™ SUPRO® isolated soy protein). Each participant was subjected to a high intensity leg-strengthening exercise and given their assigned protein supplement (20 g of protein) one hour after the workout was complete. Muscle protein synthesis was measured (by biopsy of a leg muscle) both before (as a baseline) and after the exercise bout (once 1-3 hours post exercise and a second time 3-5 hours post-exercise).

Despite the small number of participants in the study, results suggest an increase in post-exercise muscle protein synthesis by the soy/whey/casein combination group relative to the whey only participants. The authors concluded that the combination of slow, medium and long-digestion time proteins may lengthen the post-exercise recovery window, thereby allowing for potentially bigger strength gains than might be expected by using any one of the proteins by itself.

I want to know more; don’t you? I’d love to see this study extended over time to see if a longer post-exercise recovery window really results in improved strength in the gym. For example, assigning athletes to different protein supplementation regimes and measuring their 1RM on a standard strength exercise weekly for several months.

I’d also like to know whether the results are applicable to women; I work hard in the gym and if changing the type of protein I consume post-workout can give me better and faster results, I’m all for making a change.

Join me at a Twitter chat with Solae and FitFluential on Wednesday, May the 23rd, 8:00 pm CST (that’s 6 pm if you’re on the west coast). Follow my Tweets (fitknitchick_1) and the hashtag #SoyProtein for more information about soy and the benefits of including it in your post-exercise regime.

FitFluential LLC compensated me for this campaign. All opinions are my own.

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  1. I too, would love to see more studies that use women so we can definitively say yay, nay, whey! Good luck with your weight training goals.
    KymberlyFunFit recently posted…Post-Workout Protein: Soy RevisitedMy Profile

    • There’s a long history in the medical/physiological/pharmacological literature of using only men as subjects for research. Probably because, in the past, it was primarily men conducting the studies!
      Also, women are much more complicated… (in a good way!)

  2. I agree, I would love to see more studies that use women. Yup, we’re more complicated, but that probably means we need the studies more!
    Felice @ The Happy Runner recently posted…Favorite arm exercises for runners.My Profile

    • I believe that the researchers may have already done some work on women and strength and soy. Stay tuned for more info!

  3. And I am curious to see how this research extrapolates out to older adults with sarcopenia. I wonder if it can even help with its prevention. Once the research is published, I’ll be looking into this further.

    • You and me too!
      I have so many clients and class participants who are moving into that ‘older adult’ demographic. (And of course, I’ll be there before long too!)

  4. and I’m the oddball who doesnt get into studies and just eats/drinks/does whatever I want! lol
    hoping to be in the chat 🙂
    Tara Burner recently posted…Turning my back on…My Profile

    • Ha, ha!
      Not so odd Tara; just happy in your own skin, doing your own thing!
      Happy Monday!

      • I have to avoid studies/research otherwise I’d be convinced I’ll die of skin cancer from my tan so I’ll just live happily one day at a time being me LOL perhaps not the most ‘educated’ way to be but it’s me…
        Tara Burner recently posted…Turning my back on…My Profile

        • Sometimes too much information can be overwhelming; especially with all the conflicting reports out there!
          I have a background in scientific research and have a hard time sorting it all out…

          • Ive never been a scientific/research/technical info type…and I go into info overload quickly prob part of the reason I never ever ever watch the news either…I’ll just stay oblivious in my own little world LOL and rely on others to tell me any earth shattering news I need to know about! 🙂
            Tara Burner recently posted…Turning my back on…My Profile

  5. Interested in this due to the conflicting studies of soy & older women.

    As for whey – I use the isolate for quick release after a workout and I whey/casein combo for slower release & thus having energy for my next workout.

    Looking forward to your chat! 🙂
    Jody – Fit at 54 recently posted…Gratitude Monday & Giveaway Love!My Profile

    • I have to say, that before I participated in this campaign with Solae, I had no idea about the differences between whey and casein. I’ve always just used whey! I could use energy for the next day’s workout, so I’m thinking I need to branch out a bit!

      Hope to see you at the Wednesday night chat!

  6. I’ve only just started taking protein after intense work outs this year. I wish I had of been on to it a little earlier as one of the personal benefits I have noticed is (as you mentioned) a reduced craving for carbs because I feel full for longer. I used to put so much emphasis on getting fit but neglecting my diet!!
    kirri White (@kirri_white) recently posted…Celebrate your SuccessesMy Profile

    • As you know, nutrition and exercise go hand in hand; “can’t have one without the other”!

      I also didn’t know about slow vs. fast acting proteins. I love that we can extend the post workout repair window by choosing a variety of proteins to add to our shakes!

      Have a great week, Kirri!

  7. I have used Genisoy in the past and quite liked it. Always open to new and recommended products.

    Hope to get in on the Twitter chat.
    Elle recently posted…Getting My Groove BackMy Profile

  8. Interesting! Will try and join in on the twitter chat! Thanks for sharing this 🙂
    Kierston recently posted…Just When I Thought I Was Done…My Profile

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