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Default Is Soy That Bad?
by BendtheBar 10-21-2011, 12:27 PM

Is Soy That Bad?

T NATION | Is Soy That Bad?

Call me a naďve optimist, but every month that passes without a mention of soy protein in health and performance media fills me with hope that the soy plague has finally ended.

Then, there it is again in a headline, "Is Soy That Bad?" I grit my teeth because I believe the answer is yes.

But that's never the point of the article. The author, who always used to "hate" soy products, writes about his late night epiphany that soy really isn't that bad after all.

Perhaps a supplement sponsor's paycheck caused the revelation, or maybe a new vegan girlfriend, or an unexplained rise in estrogen levels. It doesn't matter. The damage has been done – guru-certified support for soy.

In the spirit of fairness, I'll you tell what I know about soy; the good, the bad and the ugly. Let's start with the good, since it turns my stomach to even admit such a thing.

Good Soy?

In the research, when it comes to building muscle, recovering from training, or preserving muscle mass when losing weight, soy does perform well, although not as well as milk-derived counterparts.

Casein and whey and their hydrolysates are better, but soy isolate and derivatives provide amino acid spikes that both stimulate muscle growth and insulin release, another anabolic potentiator.

Read enough summaries of enough research papers and soy seems on par with bovine-spawned equivalents; maybe even better considering that soy is so damn cheap. And with Gatorade trying to run up the price of whey protein because of their G2 series, soy will probably stay much cheaper.

So do I still think that soy is really that bad? Like always, I'm inclined to go with the research and say yes, soy really is that bad.

Wait, have I become old and crotchety and stuck on my damn opinions, regardless of how stupid the truth makes me sound? I mean, hell, why learn something new? That's bullshit. I'll stick with my convictions even if they're dead-ass wrong. Now get off my lawn!

Or maybe I'm just not sharing all that I know?

Look, I'm not stupid. I know solid research that proves I'm wrong is as valuable as research that proves I'm right, because I always want to improve and refine my work. I admit when I'm wrong and in the case of soy, the research has only solidified my position that soy protein is junk for athletes.

To determine that, however, I had to do something considered extreme and unheard of since the arrival of PubMed: I read the full articles.

Had I stopped with the abstracts like 90% of internet info junkies, I would've been forced to take the researchers at their word, put my tail between my legs and admitted I was wrong, and reformulated my protein suggestions to use cheaper ingredients like soy.

However, included in peer-reviewed articles, when applicable, is a list of materials used for the experiment and their source. The soy and other protein powders tested come from specialized formularies that create small batches of purified material. Researchers want to test the peptides and not all the extra junk included with typical brick-and-mortar store brand products. Sometimes the formulae are so pure, scientists can administer them intravenously!

But I've never bought anything that good, and I bet nobody else reading the muscle mags has either.

Now, by junk, I don't mean the lead or cadmium that Consumer Reports found in various popular brands of protein powders like Muscle Milk. I'm talking about stuff that's far more heinous, at least when considered in the context of strength training. (Lead might decrease intelligence, but I don't think anyone resistance trains for a swole IQ.)

The Main Villain

I'm such an adamant opponent of soy – and probably always will be – because of the trypsin inhibitors it contains.

Trypsin inhibitors are chemicals that prevent the digestion of protein. Trypsin is an essential enzyme in the gut for digesting intact proteins. By cleaving long protein chains into smaller bits, trypsin allows dietary protein to pass through the walls of the digestive tract and into circulation where it becomes the raw material for muscle, connective tissue, organs, and what not.

Basically, without trypsin, the protein portion of your meals is going nowhere except right out your back end and down the toilet.

There are supplements on the market that circumvent trypsin, mind you, like amino acid supplements and hydrolyzed proteins, but other proteins would get wasted if there wasn't any trypsin, or if something neutralized the trypsin.

Commercial soy products, even isolates and hydrolysates, do just that – they neutralize trypsin. That's what places trypsin inhibitors into a unique category of consumables called anti-nutritive factors.

Anti-nutritive means exactly what it says; it destroys the nutrition of an entire meal. In soy's case, the anti-nutritive factors do the worst thing possible for an athlete by preventing the digestion of protein.

For example, beef, eaten alone has a biological value of about 90. Mix in a little soy and it drops to 26. Concerning absorption, that's a drop of 70%.

No big deal, right? Soy is cheap. Drink up, add in another 50 or 60 grams to compensate for the loss. Heck, why stop there? It's so damn cheap, just drink a ton of it and call it a day.

That misses the point completely. Soy neutralizes trypsin, meaning it eliminates the ability to digest any intact protein. It doesn't matter how much extra protein comes down the pipe, it won't get used. It's far simpler to just carry your chicken, eggs, and beef to the bathroom and feed the ravenous porcelain god by hand.

Soy isolates won't help. They're not that isolated. Sure, it's almost all protein, but the trypsin inhibitors are proteins too. Most isolates still contain 20 to 50% of the trypsin inhibitors of intact soy.

There's no escaping the trypsin inhibitors without ordering from the same German dispensary where the researchers order their soy isolates, which I can almost guarantee isn't as affordable as the highest quality casein hydrolysates, such as those found in Anaconda™ Anabolic Load and Mag-10® Anabolic Pulse – which also perform better in every way compared to the hydrolyzed soy equivalent.

The Soy Truth

That's what happens when you read the entire research paper and don't rely on the author's synopsis, which often doesn't contain enough information for a solid assessment of the findings.

In this case, experts randomly suggest including a protein that will in reality prevent the digestion of all protein.

I covered the good and bad of soy. As for the ugly? Well, let's say it's what the toilet deals with in a soy-lover's household.


Abdel-Aziz S, Hussein L, Esmail S, el-Awadi N. In vivo rat assay for true protein digestibility and protein quality of beef and meat products extended with soy protein. Int J Food Sci Nutr. 1997 Jan;48(1):51-6.

Baker EC, Rackis JJ. Preparation of unheated soy protein isolates with low trypsin inhibitor content. Adv Exp Med Biol. 1986;199:349-55.

Barth CA, Lunding B, Schmitz M, Hagemeister H. Soybean trypsin inhibitor(s) reduce absorption of exogenous and increase loss of endogenous protein in miniature pigs. J Nutr. 1993 Dec;123(12):2195-200.

Borowska J, Kozlowska H. Isolates from faba bean and soybean with lowered content of phytic acid and activity of the trypsin inhibitors. Nahrung. 1986;30(1):11-8.

Caine WR, Sauer WC, Verstegen MW, Tamminga S, Li S, Schulze H. Guanidinated protein test meals with higher concentration of soybean trypsin inhibitors increase ileal recoveries of endogenous amino acids in pigs. J Nutr. 1998 Mar;128(3):598-605.

Claessens M, Saris WH, van Baak MA. Glucagon and insulin responses after ingestion of different amounts of intact and hydrolysed proteins. Br J Nutr. 2008 Jul;100(1):61-9. Epub 2008 Jan 2.

Fernández-Quintela A, Macarulla MT, Del Barrio AS, Martínez JA. Composition and functional properties of protein isolates obtained from commercial legumes grown in northern Spain. Plant Foods Hum Nutr. 1997;51(4):331-42.

Fouillet H, Mariotti F, Gaudichon C, Bos C, Tome D. Peripheral and splanchnic metabolism of dietary nitrogen are differently affected by the protein source in humans as assessed by compartmental modeling. J Nutr. 2002 Jan;132(1):125-33.

Gumbmann MR, Spangler WL, Dugan GM, Rackis JJ. Safety of trypsin inhibitors in the diet: effects on the rat pancreas of long-term feeding of soy flour and soy protein isolate. Adv Exp Med Biol. 1986;199:33-79.

Miyagi Y, Shinjo S, Nishida R, Miyagi C, Takamatsu K, Yamamoto T, Yamamoto S. Trypsin inhibitor activity in commercial soybean products in Japan. J Nutr Sci Vitaminol (Tokyo). 1997 Oct;43(5):575-80.

Morifuji M, Ishizaka M, Baba S, Fukuda K, Matsumoto H, Koga J, Kanegae M, Higuchi M. Comparison of different sources and degrees of hydrolysis of dietary protein: effect on plasma amino acids, dipeptides, and insulin responses in human subjects. J Agric Food Chem. 2010 Aug 11;58(15):8788-97.

Phillips SM, Tang JE, Moore DR. The role of milk- and soy-based protein in support of muscle protein synthesis and muscle protein accretion in young and elderly persons. J Am Coll Nutr. 2009 Aug;28(4):343-54. Review.

Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009 Sep;107(3):987-92. Epub 2009 Jul 9.

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Old 10-21-2011, 01:14 PM   #2
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This is interesting:

The nutritional quality of soy protein products is affected by the processing conditions employed in their manufacture. Heat treatment during processing serves to inactivate the inhibitors of trypsin and chymotrypsin, enzymes which play a key role in the digestion of protein in animals. In the processing of defatted soy flour to prepare a soy protein isolate, generally no heat treatment is used. Instead, a high percentage of the trypsin inhibitors (TI) is physically removed in the whey fraction. However, depending on their mode of preparation, soy isolates may contain trypsin inhibitor activity as high as 40% of that found in raw soybeans. Using "salting in" techniques we found that a higher percentage (97.7%) of the TI was solubilized and removed with the whey fraction when the protein curd was precipitated from 0.1 N NaCl solution at pH 5.4. Using membrane techniques for the separation of TI from non-TI-protein, best results were obtained with 0.1 N. MgCl2 where 79% of the TI was removed in the permeate.
Preparation of unheated soy protein isolate... [Adv Exp Med Biol. 1986] - PubMed - NCBI
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bad, soy

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