Soy DOES NOT decrease serum testosterone in males

[Mo250]

here is the abstract

''J Int Soc Sports Nutr. 2007 Jul 23;4(1):4.

Effect of protein source and resistance training on body composition and sex hormones.

Kalman D, Feldman S, Martinez M, Krieger DR, Tallon MJ.

Miami Research Associates, Nutrition/Endocrinology Division, Miami, Florida, USA. dkalman@miamiresearch.com.

ABSTRACT: BACKGROUND: Evidence suggests an inverse relationship between soy protein intake and serum concentrations of male sex hormones. Anecdotal evidence indicates that these alterations in serum sex hormones may attenuate changes in lean body mass following resistance training. However, little empirical data exists regarding the effects of soy and milk-based proteins on circulating androgens and exercise induced body composition changes. METHODS: For 12 weeks 20 subjects were supplemented with 50 g per day of one of four different protein sources (Soy concentrate; Soy isolate; Soy isolate and whey blend, and Whey blend only) in combination with a resistance-training program. Body composition, testosterone, estradiol and sex hormone binding globulin (SHBG) were measured at baseline and week 12. RESULTS: Protein supplementation resulted in a significant increase in lean body mass independent of protein source (0.5 +/- 1.1 and 0.9 +/- 1.4 kg, p = 0.006, p = 0.007). No significant differences were observed between groups for total and free testosterone, SHBG, percentage body fat, BMI or body weight. The Testosterone/Estradiol ratio increased across all groups (+13.4, p = 0.005) and estradiol decreased (p = 0.002). Within group analysis showed significant increases in the Testosterone/Estradiol ratio in soy isolate + whey blend group (+16.3, p = 0.030). Estradiol was significantly lower in the whey blend group (-9.1 +/- 8.7 pg/ml, p = 0.033). CONCLUSION: This investigation shows that 12 week supplementation with soy protein does not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.

PMID: 17908338 [PubMed - in process]''

[Pseudonym]

Interesting. I did a bit of searching into this in response to a question here a couple of years back. I found a snippet on EndoJournals that caught my attention...

Well, I've tried to find some studies on the effects of soy in males, but haven't had much luck. All I've been able to find so far is this, and I'm not sure whether it proves anything much anyway. The main paragraph of interest is:

These findings indicated that [male] rats reared on a nominally soy-free diet had significantly larger testes and significantly lower FSH levels in adulthood and also had significantly greater body weights than males maintained on a standard soy-containing diet (Table 3); however, the scale of the differences was only in the range of 6-11%, on average, for the parameters measured.

It's interesting, but really, I'm not much wiser. If you want my completely inexpert opinion though, finish up the soy protein if you've still got some left (hell, don't waste good protein!). After that, I'd steer clear of it, as Flex says.

[Pseudonym]

^ That's perhaps not quite so relevant to your post, but I've just found this study on PubMed...

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. goodin@umdnj.edu

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.

PMID: 17416779 [PubMed - indexed for MEDLINE]

I think the main differences are that the people in your study were training (which is likely to increase the amount of testosterone anyway, sin't it?), and my study used twice the amount of soy. Still, interesting how the two studies can have such totally different findings!

[Mo250]

^ That's perhaps not quite so relevant to your post, but I've just found this study on PubMed...

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. goodin@umdnj.edu

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.

PMID: 17416779 [PubMed - indexed for MEDLINE]

I think the main differences are that the people in your study were training (which is likely to increase the amount of testosterone anyway, sin't it?), and my study used twice the amount of soy. Still, interesting how the two studies can have such totally different findings!

There was obvious flaws in thia study which they ignored on purpose so they could make their paper more interesting and get it published.

I attach the graph here. As you can see. One of the men in the studies had ~200% higher test levels at the start of the study. It sticks out like a bloody sore thumb. This data should definitely have been pulled from the average as it was obviously either experimental error or he was coming of a cycle of gear.

If you look at the graph you see that the soy had no effect on EVERY other person in the study except the one guy. So the 19% was entirely due to this guy crashing of his cycle with no PCT.

the biggest clue even just by reading the abstract that the results may be biased is the (+/-22%) part

This is an example of why you can't get by just reading abstracts.

[Pseudonym]

Bloody hell, that's shocking! In that case, I can't believe they managed to get the study published!

Thanks, mate. I'm happy to stand corrected.