Soy : not for men ?

[anthrax]

Please MS, tell me it is not true


UK researchers report that a diet supplemented with soya could lower the risk of prostate disease and atherosclerosis in healthy men.

Researchers from the University Hospital of Wales in Cardiff and the Royal Victoria Hospital, Belfast examined the effects of soya, consumed through food made with soya flour, on blood levels of sex steroids, lipids and markers of oxidative stress in a small number of men.

They write: “We have shown that soya supplements reduce serum testosterone and improve markers of oxidative stress. These findings provide a putative mechanism by which soya supplements could protect against prostatic disease and atherosclerosis.”

In the study at the University Hospital of Wales, the team carried out a randomised, placebo-controlled trial on 20 healthy volunteers, aged on average 36 years old.

The participants ate three scones every day in addition to their normal diet for a period of six weeks. The scones were made with either wheat or soya flour (containing 120 mg/day of isoflavones). Blood was analysed for sex steroids (including testosterone, dihydro-testosterone, oestradiol, oestrone, sex hormone binding globulin, albumin and the concentration of non-protein bound sex steroids were calculated), lipid profile (total cholesterol, high density lipoprotein cholesterol and triglycerides) and measures of oxidative stress (hydroperoxides, susceptibility of LDL to oxidation with copper and myeloperoxidase).

Results, published in January's European Journal of Clinical Nutrition, show that levels of testosterone fell in volunteers taking the soya scones. No significant changes were seen in the concentrations of the other serum sex steroids throughout the study, but significant improvements in two of the three markers of oxidative stress were seen in volunteers taking soya scones. There were no changes seen in serum triglycerides or cholesterol.

The authors warn that further dietary studies with clinical end points are needed to confirm the findings.

Source: European Journal of Clinical Nutrition (2003) 57, 100-106

 

[nclifter6feet6]

i take mainly soy protien and some whey in a 2 soy to 1 whey ratio of protien

im still gonna eat it!

 

[anthrax]

BUMP fo soy lovers responses

 

[ZKaudio]

lol every 3 days there is a soy club meeting here... SHHH

 

[danielson]

dammit i need mah soya milk, its got so many poly unsaturates

 

[MS]

What a dumb study design! They only measured total serum T, not free T, and given that DHT levels did not go down with the soya supplement, I think that indicates that free-T was not significantly affected (which fits well with the results of Cassidy et al (1998) and Nagata et al (2001). So who cares if your total T goes down as long as the active T and it's metabolites aren't affected????? In this same study the authors also comment (in the discussion section) "oestradiol and oestrone reduced, but not reach significance". The authors also discuss

"We found that two of the three measures of oxidative stress showed benefit
from soya supplementation. Flavonoids influence arachidonic acid
metabolism to a considerable extent (Alcaraz & Ferrandiz, 1987). The
parent compound flavone is a strong inhibitor of cyclo-oxygenase (Mower
et al, 1984) and has free radical scavenging properties (Sweis et al, 1984).
A probable mechanism of flavonoid interaction with prostoglandin
synthetase may be through antioxidant or free radical scavenging (Buck,
1996), the antioxidant activity being related to inhibition of lipo-oxygenase
(Middleton & Drzewiecki, 1982). There is evidence that products of cyclo-
and lipo-oxygenase such as organic peroxides and free radicals are involved
in the aetiology of malignancy (Cerutti, 1985). Reductions in antioxidant
capacity and elevations in peroxidative damage with increasing age are seen
in rat prostates (Ghatak & Ho, 1996). The inhibition of these enzymes by
flavonoids may be a mechanism by which they could be protective against
prostatic malignancy, and may also be relevant to protection against
atherosclerosis."

All in all, soya in moderation still seems like a GOOD thing on balance, with proabaly very little impact on functional testosterone levels in men, and favorable impact on estrogen metabolism in women (and probably men too). I might add that the isoflavone content of 120mg per day they gave these guys is equivalent to the amount of isoflavones you would get from around 180g of soy protein isolate which is a truckload of soy protein everyday!!!!! In this experiment they used soy flour, which is much higher in isoflavones for the amount of protein you get out of it. I would suggest that if you are really worried about isoflavone intake but want a good, cheap protein that you stick to the soy protein isolates.