The Truth About Soy Protein Isolate and Other Urban Soy Myths
How does this happen, you might ask?
It usually starts with an irresponsible blogger or web site author who likes to write sensational stories – and doesn’t let the facts get in the way of a good story. They usually start out with a kernel of truth and then distort it and magnify it until it becomes unrecognizable – all in hope of having a sensational story to tell.
I’ll give you some specific examples in a minute.
Some of these authors have doctor title attached to their name, so it is not easy to identify which sites are providing misleading information and which are not. Your clue would be that most of their articles promote a miracle found or supplement to warn you of some common food or supplement that is sure to kill you. If their articles are always sensational, you can be pretty sure that all of them can’t be accurate.
And once those stories have been repeated on many sites (without anyone bothering to do a fact check)they take on the ring of truth – and become ‘urban myths”.
I’ve covered some of these urban myths about soy in the past but perhaps a brief review would be in order.
For example, one of the oft-repeated urban myths is that soy protein cancers breast cancer and certainly should not be used by any woman who has had breast cancer.
Let’s start with the ‘kernel of truth’
Soy isoflavones bind to the estrogen receptor, and some animal experiments suggested that they might increase the risk of breast cancer. While other animal experiments came to the opposite conclusion it was at least theoretically possible that soy protein might increase the risk of breast cancer and might be contraindicated for women with estrogen sensitive breast cancer. Of course, it is a far cry from saying that this is a theoretical possibility to the dire warnings that appeared on some web sites.
Of course whenever a hypothesis like this surfaces, the best way to resolve the question is through clinical studies. Three major clinical studies have been published in the last few years showing that soy protein consumption reduces – NOT increases – the risk of breast cancer.
The most compelling of these was a recent study reported in the Journal of the American MedicalAssociation (302:2437-2M3,2009). That study looked at women who had already had breast cancerand showed that soy protein consumption significantly decreased the likelihood of breast cancer recurrence – even in those women with estrogen sensitive breast cancer.
That study also showed that soy protein did NOT interfere with the estrogen blocking drug tamoxifen. In fact, it enhanced tamoxifen activity.
Unfortunately, none of the originators of the soy- breast cancer warning have seen fit to alter their websites based on the actual clinical data, so this urban myth persists.
Another urban myth is that soy protein consumption will affect male fertility.
The “kernel of truth” here is that soy isoflavones also resemble testosterone. My first take on this has always been that if soy affects male fertility, someone obviously forgot to tell the Chinese. More to the point, several recent clinical studies have shown that soy protein consumption does not affect testosterone levels, sperm count or any other measure of male fertility.
And, of course, there is always the myth that soy protein consumption affects serum thyroid levels.
The “kernel of truth” here is that when taken simultaneously with thyroid medication soy protein – and many other foods – decreases absorption of the medication. However, numerous clinical studies have shown that soy protein has no effect on endogenors serum thyroid hormone levels and does not interfere with thyroid medication if taken 30-60 minutes later.
By now, many of you are probably wondering when I will get around to talking about soy protein isolate. So let me get off my soapbox and address the topic of the day I received an “urgent” email from someone last week saying that they had read that soy protein isolate was treated with strong acid, strong alkali, heated to very high temperatures and was loaded with MSG. While some of those statements can be true for hydrolyzed soy protein (more about that in a minute), none of them are true for soy protein isolate.
The first step in preparation of soy protein isolate is to remove impurities with either an alcohol or water washing process. The water washing process is preferable because it preserves the important soy isoflavones. (Shaklee Corporation uses a water washing process)
Next the protein is precipitated out of solution by adding just enough dilute acid to bring the pH to 4-5.To put that in perspective, that is 100-fold less acidic than a soft drink 10-fold less acidic than an orange and slightly less acidic than a strawberry. Finally, enough dilute alkali is added to bring the pH back to neutral (pH7). None of this requires high temperatures, and no MSG is released in the process.
Where is the “kernel of truth” here? I’m not sure, but I suspect that the original web site authors or bloggers were confusing soy protein isolate with hydrolyzed soy protein.
The term hydrolyzed soy protein or soy protein hydrolysate simply means that the purified soy protein has been hydrolyzed to the individual amino acids. This can involve treating the soy protein with strong acid at high temperature but it can also involve heating the soy protein with proteases (enzymes that hydrolyze proteins) at low temperatures. In either case, this step will be followed by adding just enough alkali to bring the amino acids back to neutral pH- If you are consuming a food or supplement containing hydrolyzed soy protein you might wish to see if you can find out which process the use.
The hydrolysis process will release MSG (the sodium salt of the amino acid glutanic acid) along with the sodium salt of all the other amino acids. Because the process occurs in our intestines we digest any protein, it is not clear that the MSG contained in a protein hydrolyzed is as harmful as extra MSG added as a flavor enhancer to foods. That remains a theoretical possibility. We’ll just need to wait for clinical studies to see if it is a real concern.
Hopefully, this “Tip From the Professor” will help you separate soy myths from soy facts. Of course, it’s not just the soy opponents that perpetuate urban myths about soy. I’ve seen lots of websites by manufacturers of soy protein and soy isoflavone supplements that make claims which go way beyond what the clinical studies actually show. The internet is truly the “wild west” of the information highway. Anything goes! You just can’t believe everything we hear.