Soy Phytoestrogens

[Ruthenian]

As the question of soy phytoestrogens has come up a few times, I thought some folks might find this quote from Dr Sears Zone interesting:

<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Significant processing of soy protein generates either soy protein concentrates or soy protein isolates. Most soy imitation meat products use soy protein concentrates as their primary source of protein. With either type of processed soy protein, the phytates that can bind minerals (especially zinc) are removed. Likewise, the protease inhibitors and haemagglutinins are deactivated by the heat treatment that is part of these more advanced processing technologies. The primary difference between the two types of soy protein is that the phytoestrogens have been completely removed from the soy protein concentrates by alcohol extraction, whereas about one-half of the original phytoestrogens remain in the soy protein isolates, which are water extracted. This is why I recommend at least one-third of your soy protein intake be in the form of soy imitation meat products, which are composed of phytoestrogen-free soy protein concentrates so that the daily phytoestrogen intake doesn’t exceed 50 mg per day.</div>

I have actually seen an article (Whey vs Soy) supposedly published originally on Elite Fitness (a heavy steroid-use web site) that maintains soy protein is the best for body building and that the weak phytoestrogens compete with the 1000x stronger natural estrogens for binding sites.  In essence, acting like Nolvadex!  Elsewhere, this is dismissed as only being of some benefit if you are on a specific anti-aromatase routine.  Can't say which is correct, but it is interesting.

I do think that the recommendation to stay below a certain level of soy phytoestrogens per day is prudent.  But, the controversy goes on ...

 

[quadancer]

Are these phytoestrogens like our mortal enemy; estrogen? Or some kind of a precursor? It would be nice to be able to enjoy cheaper shakes during the day, just on a lark, replacing endless bottles of water. And meat. Lots of meat.

 

[Aaron_F]

he is making a blanket assumption on the processing of soy. Not every manufacturer processes this way.

 

[Ruthenian]

Well, if that is the case, I guess that you would have to contact the manufacturer directly to get the answer. The problem is, you can't trust what they tell you either. I contacted the manufacturer of a certain product recently to ask about protein quality. Unfortunately, their readily available nutrition information indicated that their answer was a blantant lie (I can hardly wait to see the return email justifying their answer).

 

[Bryan Haycock]

Here's one to think about:

Cancer Epidemiol Biomarkers Prev. 2007 Apr;16(4):829-33.

Clinical and biological activity of soy protein powder supplementation in healthy male volunteers.

Goodin S, Shen F, Shih WJ, Dave N, Kane MP, Medina P, Lambert GH, Aisner J, Gallo M, DiPaola RS.

Department of Medicine, University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School, New Brunswick, NJ 08903-2681, USA.
[email protected]

PURPOSE: To determine if a commonly used soy protein supplement exhibits biological activity in vivo and in vitro, we evaluated an over-the-counter soy protein powder supplement using blood from healthy male volunteers and in an estrogen receptor in vitro assay.

SUBJECTS AND METHODS: We recruited healthy male volunteers 18 years of age or older that were in good health. Treatment consisted of consuming two scoops (56 g) of pure soy protein powder (Puritan's Pride, Oakdale, NY) daily for 28 days. Serum testosterone and luteinizing hormone (LH) levels were collected on days -7, 0, 14, and 28 of therapy, and day 42. A reporter estrogen receptor (ER) assay was used to determine the effect on ER-beta and ER-alpha in vitro.

RESULTS: Twelve subjects were enrolled with a
mean age of 32.25 years (range 25 to 47). Serum testosterone decreased 19%(+/-22%) during the 4-week use of soy protein powder (P = 0.021) and increased within 2 weeks after we discontinued soy protein powder. Serum LH concentrations decreased during the 4-week use of soy protein powder then increased within 2 weeks after we stopped the soy protein powder, but the changes did not reach statistical significance (P = 0.20). Soy protein powder
was found to induce agonist activity to ER-beta using a reporter estrogen receptor assay in yeast.

CONCLUSION: Soy protein powder decreases serum testosterone levels in healthy men and acts as an ER-beta agonist; the significance of this biological effect with respect to cancer prevention needs further study.

 

[Bulldog]

Yikes!

 

[Fausto]

Raises a question for vegetarians, some of whom relly heavily on soy products as sources of protein.

Is this a safe route or as the good Dr. says should we try to aqcuire sources that manufacture by removing the phytoestrogens?

 

[Ruthenian]

There remain a ton of unanswered questions:

- Why do some studies show no effect, while others do?  
- I've noted a few of the studies showing no effect are on older men -- are any androgen reduction effects less for middle-aged and older men?
- What component of any hormonal effects is due to soy protein itself as opposed to phytoestrogens specifically (studies that look at this seem to point to the phytoestrogens)?
- Related to that, how can we sort out the results of studies looking at &quot;soy protein,&quot; as opposed to isoflavones or phytoestogens specifically?
- How should we view the results of animal studies?
- Assuming such effects are real, what is a reasonably safe level of phytoestrogen consumption?
- Do the varying results imply that some are more sensitive to the effects?

And, do the demonstrated positive effects out weigh any negatives?

I probably get 20-60 gms/day of soy protein, but this is well below my 180-210 gm/day total protein intake.  I've got normal test levels and my PSA levels are quite low.  This would imply to me that I am somewhere near the sweet spot of getting positive influences without too much of the negative, but it would be nice to have something approaching an objective measure.