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razorcut
10-04-2005, 11:01 AM
Sorry if this has been previously addressed. Search was inconclusive.

I enjoy soy burgers a couple times per week. I've recently read (not in true medical literature) that soy can lower test levels. My questions are:

1. What are your thoughts on soy as a significant source of protein in the diet?
2. Any more info available on the soy & test issue?

Thanks in advance.

muscleup
10-04-2005, 11:45 AM
Sorry if this has been previously addressed. Search was inconclusive.

I enjoy soy burgers a couple times per week. I've recently read (not in true medical literature) that soy can lower test levels. My questions are:

1. What are your thoughts on soy as a significant source of protein in the diet?

Thanks in advance.

I think soy is one of the least significant sources of protein. There was a list posted on this site, or a link to another site that shows the best form of protein to consume, and soy was towards the very bottom.

I eat soy nuts for xtra cals, but not really for the protein.

Anthony
10-04-2005, 12:07 PM
If you google "soy testosterone" you'll get a healthy dose of info.

TheGimp
10-04-2005, 01:10 PM
Here are a few studies on the subject of soy and men:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12094627


Soy milk intake in relation to serum sex hormone levels in British men.

Allen NE, Appleby PN, Davey GK, Key TJ.

Cancer Research UK Epidemiology Unit, University of Oxford, Oxford OX2 6HE, UK. naomi.allen@cancer.org.uk

Soy beans contain high levels of the isoflavones genistein and daidzein and their glycosides and have been implicated in the prevention of prostate cancer, possibly via their effects on sex hormone metabolism. The aim of this study was to assess the relation between dietary soy intake and sex hormone levels in a cross-sectional analysis of 696 men with a wide range of soy intakes. Soy milk intake was measured using a validated semiquantitative food frequency questionnaire, and serum hormone concentrations were measured by immunoassay. Multiple regression was used to investigate the association between soy milk intake, an index of isoflavone intake, and hormone levels after adjustment for pertinent confounders. Soy milk intake was not associated with serum concentrations of testosterone, free testosterone, androstanediol glucuronide, sex hormone-binding globulin, or luteinizing hormone. These results suggest that soy milk intake, as a marker of isoflavone intake, is not associated with serum sex hormone concentrations among free-living Western men.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11880595


Hormonal effects of soy in premenopausal women and men.

Kurzer MS.

Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA. mkurzer@umn.edu

Over the past few years, there has been increasing interest in the possible hormonal effects of soy and soy isoflavone consumption in both women and men. Soy consumption has been suggested to exert potentially cancer-preventive effects in premenopausal women, such as increased menstrual cycle length and sex hormone-binding globulin levels and decreased estrogen levels. There has been some concern that consumption of phytoestrogens might exert adverse effects on men's fertility, such as lowered testosterone levels and semen quality. ... Only three intervention studies reported hormonal effects of soy isoflavones in men. These recent studies in men consuming soyfoods or supplements containing 40--70 mg/d of soy isoflavones showed few effects on plasma hormones or semen quality. These data do not support concerns about effects on reproductive hormones and semen quality.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11767208


Effects of soy protein on levels of remnant-like particles cholesterol and vitamin E in healthy men.

Higashi K, Abata S, Iwamoto N, Ogura M, Yama****a T, Ishikawa O, Ohslzu F, Nakamura H.

First Department of Internal Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan.

We determined the effects of soy protein isolate (SPI) intake on remnant-like particles (RLP), lipolytic enzymes, lipid transfer protein, transaminases, sex hormones, iron, calcium, and vitamin E in healthy men. In the first randomized, crossover experiment, 14 men were given either 20 g per day of SPI or nothing (control) for each 4-week segment. After 3 weeks of SPI intake, TG and RLP cholesterol levels were significantly lower than the baseline by 13.4% (p<0.05) and 9.8% (p<0.05), respectively. However, no significant change was found in total and low-density lipoprotein (LDL) cholesterol levels or the activities of lipoprotein lipase, hepatic lipase, cholesteryl ester transfer protein, and lecithin cholesterol acyltransferase. Although the levels of transaminases. testosterone, iron, and calcium did not change, the vitamin E level was reduced from the baseline by 9.7%, a significant decrease (p<0.01)...


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11303585


Effect of soymilk consumption on serum estrogen and androgen concentrations in Japanese men.

Nagata C, Takatsuka N, Shimizu H, Hayashi H, Akamatsu T, Murase K.

Department of Public Health, Gifu University School of Medicine, Japan.

... We conducted a randomized dietary intervention study to determine the effects of soy consumption on serum levels of steroid hormones in men. Thirty-five men were randomly assigned to either a soymilk-supplemented group or a control group. The men in the soy-supplemented group were asked to consume 400 ml of soymilk daily for 8 weeks. The men in the control group maintained their usual diet. Blood samples were obtained just before the initiation of the dietary period and thereafter every two weeks for 12 weeks. Changes in hormone concentrations were analyzed and compared between the two groups using the mixed linear regression model against weeks from the start of the dietary period. The mean (SD) soymilk intake estimated from dietary records during the dietary study period was 342.9 (SD, 74.2) ml in the soymilk-supplemented group. There was a significant difference between the two groups in terms of changes in serum estrone concentrations, which tended to decrease in the soy-supplemented group and increase in the control group over time. None of the other hormones measured (estradiol, total and free-testosterone, or sex hormone-binding globulin) showed any statistical difference between the two groups in terms of patterns of change. The results of the study indicate that soymilk consumption may modify circulating estrone concentrations in men.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10798211


Inverse association of soy product intake with serum androgen and estrogen concentrations in Japanese men.

Nagata C, Inaba S, Kawakami N, Kakizoe T, Shimizu H.

Department of Public Health, Gifu University School of Medicine, Japan.

The cross-sectional relationships of soy product intake and serum testosterone, estrone, estradiol, sex hormone-binding globulin, and dihydrotestosterone were examined in 69 Japanese men. Soy product intake was estimated from a semiquantitative food frequency questionnaire. Serum estradiol concentration was significantly inversely correlated with soy product intake (r = -0.32, p = 0.009), and serum estrone concentration was nonsignificantly inversely correlated with soy product intake (r = -0.24, p = 0.05) after controlling for age, body mass index, smoking status, and ethanol intake. Total and free testosterone concentrations were inversely correlated with soy product intake after controlling for the covariates, but these correlations were of border line significance (r = -0.25, p = 0.05 and r = -0.25, p = 0.06, respectively). Similar correlations were observed for these hormones with isoflavone intake from soy products. The data suggest that soy product intake may be associated with the endogenous hormone levels in Japanese men.

Summary: Soy will most likely not negatively impact your testosterone levels. The latter two studies even suggest that soy consumption could reduce estrogen levels in men.


I think soy is one of the least significant sources of protein. There was a list posted on this site, or a link to another site that shows the best form of protein to consume, and soy was towards the very bottom.


Depending upon which measure of protein quality you use, soy rates right up there with eggs, milk and better than red meat:

http://en.wikipedia.org/wiki/PDCAAS


Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method of evaluating the protein quality based on the amino acid requirements of humans. The PDCAAS rating is a fairly recent evaluation method (it was adopted by the US Food and Drug Administration in 1993) and emerged due to weaknesses in earlier evaluations of protein quality, such as the Protein Efficiency Ratio (PER) and the Biological Value (BV).

A PDCAAS value of 1 is the highest, and 0 the lowest. Some ratings of commons foods include soy (1.0), egg white (1.0), casein (1.0), milk (1.0), whey (1.0), beef (0.92), kidney beans (0.68), lentils (0.52), peanuts (0.52), wheat (0.25).


I eat soy nuts for xtra cals, but not really for the protein.

An excellent source of healthy fats in addition to the protein.

razorcut
10-04-2005, 01:36 PM
Thanks all.

Special thanks to TheGimp. That's exactly what I was looking for.

Built
10-04-2005, 01:38 PM
Killer post, Gimp. Thanks!

muscleup
10-04-2005, 01:58 PM
HERE (http://www.bodybuildingpro.com/proteinrating.html) are some protein ratings based on Biological Values (BV refers to how well and how quickly your body can actually use the protein you consume.)

I think this is what I was refering to earlier about soy having a low BV. Just didn't have the time to look it up.

TheGimp
10-04-2005, 03:35 PM
Yes, the different measures seem to have wildly differing opinions on the quality of soy.

A couple of points taken from the link I posted above (http://en.wikipedia.org/wiki/PDCAAS):


The PER was based upon the amino acid requirements of growing rats, which are noticeably different to that of humans

Specifically, rats are covered in fur. Soy is low in the amino acid methionine, which is used in the growth of this fur. Thus soy is a poor protein source for rats and it scores poorly using the PER. Taken from Will Brink's "The (Partial) Vindication of Soy" (http://www.mesomorphosis.com/articles/brink/soy-protein.htm):


Rats fed soy protein enriched with methionine grew at a similar rate as those fed casein

Back to the Wikipedia entry:


Similarly, amino acids that are lost due to antinutritional factors present in many foods (such as tannins in soy) are assumed to be digested by the PDCAAS

Which does call into question the high score that soy receives using this method.

One particularly important point to take into account however, is what the soy is being consumed with. In particular, the exact ingredients of the soy burgers. Take Boca Burgers for instance (http://en.wikipedia.org/wiki/Boca_Burger):


WATER, SOY PROTEIN CONCENTRATE, WHEAT GLUTEN, CONTAINS LESS THAN 2% OF METHYLCELLULOSE, SALT, NATURAL AND ARTIFICIAL FLAVOR, DRIED ONIONS, MALTODEXTRIN, YEAST EXTRACT, SESAME OIL, DEFATTED WHEAT GERM, HYDROLYZED PROTEIN (CORN AND SOY) AND HYDROLYZED WHEAT GLUTEN, CARAMEL COLOR, SOY SAUCE (WATER, SOYBEANS, WHEAT, SALT), AUTOLYZED YEAST EXTRACT, DISODIUM GUANYLATE, DISODIUM INOSINATE, SUCCINIC ACID.

Like many veggie burgers, it's made with a blend of soy and wheat proteins (the wheat gluten), which is going to result in a higher quality protein source than one of them alone (http://en.wikipedia.org/wiki/PDCAAS again):


For example, grain protein has a PDCAAS of about 0.4 to 0.5, limited by lysine. On the other hand, it contains more than enough methionine. White bean protein (and that of many other pulses) has a PDCAAS of 0.6 to 0.7, limited by methionine, and contains more than enough lysine. When both are eaten in roughly equal quantities in a diet, the PDCAAS of the combined constituent is 1.0, because each constituent's protein is complemented by the other.

P.S. Thanks Built, that means a lot coming from your fine self ;)

getfit
10-04-2005, 03:36 PM
awesome reads gimp :)