T-men and T-vixens, check out this new study on soy protein. Although in this study the animals got either soy or casein only for 15 weeks and most people would not only eat soy protein alone for that period of time, it kind of makes you want to rethink using soy as your main protein source. Basically the researchers found that soy protein accelerates protein breakdwown (preferentially in myofibrillar - muscle - protein) due to rises in cortisol/glucocorticoids from soy consumption. I think that some soy in your diet (from cereals or bars) will not harm you at all but big soy meals or taking most of your protein from soy is not beneficial.
Br J Nutr 2001 Apr;85(4):447-57
Activation of skeletal muscle protein breakdown following consumption of soyabean protein in pigs.
Lohrke B, Saggau E, Schadereit R, Beyer M, Bellmann O, Kuhla S, Hagemeister H.
Research Institute for Biology of Farm Animals, Dummerstorf-Rostock, Department of Animal Nutrition, Germany. loehrke@fbn-dummerstorf.de.
Diets with protein of inferior quality may increase protein breakdown in skeletal muscle but the experimental results are inconsistent. To elucidate the relationship, pigs were fed isoenergetic and isonitrogenous diets based on soyabean-protein isolate or casein for 15 weeks, with four to six animals per group. A higher plasma level of urea (2.5-fold the casein group value, P = 0.01), higher urinary N excretion (2.1-fold the casein group value, P = 0.01), a postabsorptive rise in the plasma levels of urea, 3-methylhistidine and isoleucine in soyabean protein-fed pigs suggested recruitment of circulatory amino acids by protein breakdown in peripheral tissues. Significant differences between dietary groups were detected in lysosomal and ATP-dependent proteolytic activities in the semimembranosus muscle of food-deprived pigs. A higher concentration of cathepsin B protein was found, corresponding to a rise in the cathepsin B activity, in response to dietary soyabean protein. Muscle ATP-stimulated proteolytical activity was 1.6-fold the casein group value (P = 0.03). A transient rise in the level of cortisol (2.9-times the casein group value, P = 0.02) occurred in the postprandial phase only in the soyabean group. These data suggest that the inferior quality of dietary soyabean protein induces hormonally-mediated upregulation of muscle protein breakdown for recruitment of circulatory amino acids in a postabsorptive state.
Very interesting study, are you in the research field? I’m working on a Phd in nutrition, using pigs as a model for humans, so this study caught my attention. I will definitely get the reference. We have done some work with isoflavones in pigs, so this also might be of some interest to one of my co-workers…Thanks…good post!
I’ve been a vegetarian for the past 3 years so soy has been my primary source of protein for that time. I can’t see changing one of the main staples of my diet just based on what some study says. I’ve worked out regularly and have been able to maintain the same level of strength and muscle that I had 3 years ago so soy can’t be that bad.
I gained 20lbs on a vegan diet of the course of a year. Soy protein isolate and soy products were my main source of protein. So yes, dman, it can be done
The question is, Mike, would you have done even better if you had eaten normally? And what about long term? I don’t know, man, it’s not just T-mag. Every time I go to health central and look up studies they also conclude with the same thing: Men should avoid soy.
Good comment Mike Mahler, maybe others will see that soy isn’t as bad as some people make it out to be. If you look as ALL the research on soy instead of picking out a study here and there, you’ll see that soy is not only the best source of protein but probably one of the best all around foods. In fact, if I were forced to eat a diet consisting of only one food, I think soy would be it.
LOL. Yeah, I’m almost positive that John is in the research field. What’s that awesome stuff he formulated again…ah yes Surge! Sorry, I love to be a smart ass. Must be my youth. John is an exercise biochemist and an avid researcher.
Ok, now for the can of worms which has once again been opened. The issue IS NOT whether soy will cause you to constantly lose muscle and atrophy to the size of an ant, but that it is inferior to other sources of protein and yes deleterious to your efforts via reduction in testosterone, or by directly being somewhat catabolic to muscle tissue as John pointed out, as well as other possible mechanisms. WHEN COMPARED to something like whey or casein. Oh, and please I don’t want anyone saying they used casein or whey for a month and then soy for a month and soy was just as good. How do we know you controlled for other variables in your diet, training, etc. The only way to know is through a controlled study.
Tek, who knows, and what is eating normally? what you do? I think if you get enough calaroes and protein the source is not that important. Hell, Rama the famous Indian wrestler was 5’11 and 260lbs of muscle and he was a strict vegetarian eating primarily a fruit based diet. Stephen Arlin, author of “Raw Power” is a stric rawfood vegan and is 6’1 and weighs 225. He can benh press 315 15 times and has stated in interviews that he got much stronger on a a rawfood diet. All meat is is concentrated plant protein. After all animals that you eat, probably eat grass. Thus, I am just taking the middleman out and going to the source. I do not have any problems gaining or losing weight on a vegan diet.
People are omnivores. Period. Eating like a cow all your life is not natural. Our closest relatives, the apes, are also omnivores. They eat meat when they can get it. Is that “unnatural” for them? Just out of curiosity, and this is not a slam, why are you a vegetarian? Obviously it was a choice you made along the way.
Tek, I have up meat and dairy years ago for ethical reasons. I do not like the way that animals are treated on factory farms and do not want to be a part of their unnecessary suffering. If I had my own eggs and cows, I probably would not have a problem with eating eggs and dairy.
“Swoledog”, you’re a bit sensitive arent ya? I was just joking since Ive written at least 2 dozen articles at t-mag with my credentials at the end of each one (“John M Berardi is a scientist and PhD candidate in the area of Exercise and Nutritional Biochemistry at the University of Western Ontario, Canada. He also serves as a nutrition and training consultant to numerous athletes including US Olympic and NCAA track and field athletes, world-class endurance athletes, collegiate and professional football players, strength competitors, and bodybuilders. You can contact him for professional consultation at JMBMUSCLE@hotmail.com”). In addition, I answer questions here all the time, posting research findings from the literature as well as from my lab. I apologize if you are new here and didnt know this. But either way, if you are going to try to slam me “YOUR NO BODY TO ME” please at least get the grammar correct; it should be “YOU’RE NOBODY TO ME”. Ok, now we’re even…Another JOKE!
Anyway, it’s nice to see some other researchers on here. Please feel free to contribute some of the cool things from “your world” from time to time so that we can argue them here.
If you read the abstract the researchers clearly state that SOY IS AN INFERIOR PROTIEN. It is low in some critical amino acids. Now, if taken in a mixed diet, I think that it can be ok. But I certainly wouldnt want to make it the bulk of my diet. I figure it this way…the research on the whole points to its inferiority for BB purposes so why chance it. If it sucks, then I lose. If it doesnt suck, then cool but its certainly not BETTER than milk proteins or animal. Id rather not take the chance with my development. The evidence points to casein, whey, and animal proteins as better. So Im goin safe and sticking with them. But like I said, I do get some soy in my bars and I do get some in my cereal (VIVE)…the cereal is canadian and contains a nice profile 8g P, 21g C, 1g F. Protein comes from soy. I get about 2 servings of this per day (16g of my 350 come from soy).
I am with Mike on this one. I still don’t think soy is as detrimental as this forum has been saying. Everybody in the research field knows that animal studies almost never correlate to human studies. When you give me a double blind study on humans then I might listen. I have been consuming soy protein for 7 years and in that 7 years I have gained 15-20 lbs of lean body mass. I am 6’1" 218 and I am not bragging but there are many people who ask me if I do steroids. That is a great compliment to me. The verdict is still out on soy.
Like a twilight zone episode.