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Question:
I always hear about the benefits of soy protein but you are totally against it. What is so bad about soy protein?


Answer:
Soy protein is just not a very good protein for building muscle. Its biological value is low and it contains large amounts of naturally occurring toxins that many food scientists refer to as antinutrients. Among these antinutrients are enzyme inhibitors that block the action of trypsin and other critical enzymes involved in protein digestion. These inhibitors can cause gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. Studies have also shown that diets high in trypsin inhibitors can be carcinogenic.
Soy contains haemagglutinin, a clot-promoting chemical that causes red blood cells to clump together. And soy also contains phytic acid that can block the uptake of essential minerals - calcium, magnesium, copper, iron, and zinc - in the intestinal track. These chemicals are called "growth inhibitors".

An equally nasty component of soy protein is its high isoflavone content. Isoflavones are estrogen-like compounds also called natural estrogens. In fact just 100 grams of soy protein has the estrogenic equivalent of a typical birth control pill. Studies have also shown isoflavones inhibit the synthesis of certain steroid hormones and inhibit beta-hydroxysteroid dehydrogenase - the key enzyme that converts pro-hormone compounds into testosterone.

It amazes me that some supplement companies ignorantly continue to market isoflavones such as chrysin as a way to promote testosterone production and inhibit estrogen when, in fact, it does just the opposite. It increases estrogen and decreases testosterone. Ever wonder why those andro supplements that contained chrysin never worked? Now you know.

These are a few major reasons why soy protein and its isoflavone content are not only poor nutritional sources for building muscle, but there is mounting evidence that they can actually stunt growth and may be harmful to your health.

I know this is probably exactly opposite of what you've been told by the "spin-doctors" that are promoting their supplements, but if you take a good look at the research you'll discover there are many things they say that doesn't mesh with the science.



Answered By Paul Delia
AST Sports Science
Originally posted: 7/31/2000

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Humans aren't monkies. The reason why you get conflicting results.

lol ok you win. so soy is bad

Well, you were close Verb....I mean, humans do share 99% of our DNA with monkeys, but that 1% is a giant difference. If you can find an average human pulling a thousand pounds more than their body weight, then I'll take your study!

i can pull 1000 pounds more than my body jk thats insane that monkeys can do that

They meant two different groups, one with soy and one with egg.

By the way, the trypsin inhibiting effect is not present in tofu and tempeh products. It is also eliminated if soybeans are cooked well. I'm not sure about TVP (textured vegetable protein, which is actually soy) but I've heard that many of the manufacturers take pains to eliminate the trypsin inhibitors. I would have to contact them to be sure. The trypsin inhibitors make soybeans hard to digest. I'm not sure that sweeping statements like the trypsin inhibitors cause chronic defeciencies in amino acid uptake are accurate. I think it is only an acute effect. However, if the large bulk of your protein intake is in the form of soy protein powder, then change that word to chronic. Therein lies the problem.

I don't think that eating a moderate amount of soy is going to cause chronic anything.

Phytic acid is a bean and grain thing. Soybeans do contain a large amount of it. Again, not a problem in the traditional soy foods. Easily eliminated from beans and grains by soaking and rinsing.

Let me be the devil's advocate. Ever hear the expression everything in moderation? It's a pretty useful saying. And it applies to just about every food you can imagine. Soy has sometimes been linked to thyroid problems. Guess what? Broccoli, one of the most revered vegetables around, contains five, count them, five goitrogenous compounds that interfere with the use of iodine in the thyroid. Does this mean that you are likely to have a problem even if you have thyroid deficiency? Probably not. You are just not likely to eat enough of brocolli to cause the effect.

Here's a shocker: brocolli juice is not good for infants. No surprise there, right. Yet it seems to come as a surprise that soy based infant formulas are not such a good thing. If someone was to start marketing a broccoli supplement for infants, and then babies started dying, would we attack broccoli? Or, if someone was making highly concentrated brocolli body building supplement (hypothetically), and it was linked to all sorts of negative effects? I don't know if we would condemn broccoli, but it would be silly to do so.

Much of the negative press that soy gets is because of its use in infant formulas. That's one of the things that started the whole debate. Infants and adults are not the same, right? They cannot eat the same things, and things affect them differently. Kind of like humans and rhesus monkeys.

You shouldn't eat huge amounts of broccolli or any other plant, for that matter. That's why I'm comparing soy and brocolli. They are both of the plant kingdom and they both contain powerful chemicals. I could give a long list of plant foods with similar attributes. Constituents that may beneficial in moderate amounts and harmful or even posonous in large amounts.

Tomatoes, for instance. They are of the nightshade family. Potatoes and eggplants too. Contrary to popular belief, it's not just the tomatoes plant that contains the poisons, the fruits do too, only in smaller amounts. Kind of makes it seem like you could eat too much tomato, doesn't it? Especially if it was some kind of tomato concentrate. Try eating 100 grams worth of double concentrated tomato paste a day for a couple of weeks and see how it works for you. Sounds ridiculous doesn't it?

So, I disagree that soy is bad. I agree that soy protein powder is bad or at least not a good idea. I wouldn't touch it. I don't think for a second that soy, as it has been traditionally consumed, in moderate amounts is a problem. I'm also not going off of broccoli and tomatoes.

It isn't at all beneficial to bodybuilders anyways. Besides all the studies like the one I posted about a decrease in test, it has a poor bioavailability so if anyone can avoid it, do so. Bottom line. Buy whey/casein and soy can take a back seat. If the medical (controlled) studies don't sway you, the bioavailability score should if you are serious about the gym.

I do agree that it probably won't make a profound difference it test production, but I wouldn't waste money on it since I'm trying to stay HUGE!!

I agree. I wouldn't waste money on a soy protein powder.

And if you don't like soy products like tofu, tempeh, or all the mock meat stuff then ok. But it's gonna take a huge amount of those weak plant estrogens to effect you test, and its gonna take that extended period of time.

But the BV rating is a crock. It is not considered reliable or accurate by today's standards and just about every method that has come after it has been shot down. I think some of us are suffering from selective research syndrome.

Consider this for an updated perspective.

Nutritional Value of [15N]-Soy Portein Isolate Assessed from Ileal Digestibility and Postprandial Protein Utilization in Humans

François Mariotti*, Sylvain Mahé*2, Robert Benamouzig, Catherine Luengo*, Sophie Daré*, Claire Gaudichon* and Daniel Tomé*

* Institut National de la Recherche Agronomique, Unité de Nutrition Humaine et de Physiologie Intestinale, Institut National Agronomique Paris-Grignon, 75231 Paris Cédex 05, France and Service de Gastroentérologie, Hôpital Avicenne, 93009 Bobigny, France.

ABSTRACT
The purpose of this work was to assess the true oro-ilea digestibility, and to concurrently quantify the deamination of absorbed dietary nitrogen to examine the postprandial nutritional value of a soy protein isolate (SPI) in humans. To assess bioavailability and bioutilization of SPI, 10 healthy volunteers ingested 30 g of SPI, intrinsically and uniformly [15N]-labeled, added with 100 g of sucrose and water up to a final volume of 500 mL. True ileal digestibility was assessed by the [15N]-dilution method for 8 h by means of a naso-intestinal intubation technique. To describe and quantify exogenous nitrogen deamination for the same time period, urine and plasma samples were collected. True oro-ileal digestibilityof SPI nitrogen was 91%. The amount of absorbed SPI amino acids used for nonoxidative disposal, i.e., postprandial biological value, was 86% 8 h after meal ingestion. Hence, net postprandial protein utilization of SPI was 78%. Compared to previous data that were assessed under the same condition in humans, the nutritional value of SPI is 92% of that in milk protein concentrate.

Now, the common BV value for soy protein is around 74 or 75%. The PDCAAS (Protein Digestibility Corrected Amino Acid Score) is .91 (1 is the higest). In this study the true ileal digistibility of soy was found to be 91%. The BV is always found to underestimate values compared to new methods.

Now, do those phyto-estrogens do more than just bind to estrogen receptors thereby blocking them, or do they initiate estrogen production?

I'm sure you've read that they do on a lot of the BB web sites. But the studys that found this were done on mice and rats. If you want to believe that than we have to relax the criteria that has been initiated on this thread. If verb's rhesus monkeys weren't good enough, then...

And all those consclusive studies? Remember the words statistically insignificant? Add this:

Agency for Health Care Research and Quality (AHRQ)

Authors: Balk E, Chung M, Chew P, lp s, Ramon G, Kupelnick B, Tafsioni A, Sun Y, Walk B, Devine D, Lau J
Endocrine Function

Measures of endocrine function were reported from 50 trials in 47 articles. Five studies with a total of 179 participants reported testosterone levels in healthy males before and after soy consumption. Four of these trials found a statistically non-significant decrease in testosterone levels. The small total number of subjects as well as the low quality of these studies precluded any meaningful conclusion. No statistically significant effect was found on FSH level, which is commonly measured in the initial evaluation of male and female infertility; results were conflicting.

Look, I've done a lot of this kind of research. It used to be my job to do this kind of research. Things are just never simple and cut and dry. People can believe what they want to believe. But I would never tell someone, "Look, soy is gonna lower your test." Because I don't base things on what I believe. I either know or don't know. And I don't know if soy really effects your test. I do think it is likely that a large amount of soy can lower test, but I don't know just based on a bunch of faulty studies.

Do we understand the term statistically insignificant? It means the the results can be explained by normal metabolic processes, i.e. natural fuctuations in test level that stay within a normal range.

You can make an informed decision based on the info you have. I certainly never use soy powder and only eat some soy in my diet. But I'm not gonna sublime an entire industry or make claims on the bio-availibility of soy based on outdated research.

Here is a good overview of some of the problems with this kind of food research:
Future Research

This report dealt with a broad range of health conditions and endpoints, thus it is difficult to focus research recommendations on a specific area. Common to most bodies of evidence regarding medical fields, better quality, well-reported, larger and longer duration studies are needed to address the questions of interest. Future studies should fully report the components of soy products being tested; compare different doses, soy products, and populations; more closely evaluate the effects of different soy components, including non-protein, non-isoflavone components; fully consider the types of foods being replaced by soy products and the controls being used; and use the CONSORT statement as a guide to designing and reporting studies. 3,4
Conducting clinical trials in the area of health effects of food substance is fraught with difficulties. There is a complex interplay among the various components and potentially active substances within the foods and with other foods, dietary variations, as well as with other lifestyle and clinical variations among individuals. Controlling for these factors is difficult within a trial. Interpreting discrepant results among trials is even more difficult. Isoflavones are believed to be the key active substance in soy, but this is by no means certain. Little data suggest that the amount of soy isoflavones is associated with an incremental effect and studies of soy protein with little or no isoflavones frequently had similar effects as isoflavone studies. Difficulties with attempting to ascribe a food health benefit to a specific component of the food are highlighted by the recent spate of disappointing results from antioxidant trials, which suggest that the evaluation of potential nutrient benefits may need a paradigm different from the traditional clinical trial model.
The bioavailability of an ingested nutrient may also be an important factor in the determination of the beneficial effect. Several factors may affect the bioavailability of ingested nutrients:

1. Absorption rate, affected by the interactions with competitive nutrients, the usual diet compositions, and types of foods or supplements.
2. Incorporation rate into the blood stream, in which complex mechanisms might be involved, such as the functions of facilitated transporters, receptors on the membrane, or cellular binding proteins.
3. Metabolism of the intestinal bacterial environment.

Any one of these factors alone does not determine the bioavailability. In order to gain insights on the question of dose-response relationship, we not only need the information on the soy isoflavone contents, including types and amount, but also on the bioavailability of the ingested soy isoflavones.

Unfortunately studies that attempt to control for the myriad factors that interfere with clear interpretation of the effect of food products such as soy tend to be highly artificial, with little applicability to the average person. Clarity is needed to define what study questions are of interest. Metabolic laboratory studies or investigations of highly structured or restricted diets (such as those where soy protein constitutes the bulk of daily protein consumption) are of potential value only to possibly determine which components of soy are bioactive or to determine what extremes of diet may be necessary to achieve a benefit. Studies that substitute practical amounts of soy products into average people's diets would better address the question of whether people should make the effort to include more soy in their diets, but these studies will invariably be difficult to interpret. An exception to this may be studies of soy isoflavone supplements (e.g., non-food capsules), which may be interpreted more like usual drug trials.

Carefully controlled efficacy studies (those conducted under the artificial conditions of a clinical trial) may still be useful to pin down the relative effects of various components of soy. Once this is better clarified, more practical effectiveness studies (that aim to test the value of an intervention in more real-world scenarios) with feasible interventions might be more important.

Hey, for every "expert" who says soy is not good for bodybuilders you can find another who say it is, or advocates mixing soy and whey in you diet, so on and so forth.

Who really knows? I say don't be too paranoid about soy. The jury is still out, and will be for a good long time.