I4L, here is another view from a controversial BB'er. Seems to be a lack of in depth, hard data on this subject. FWIW

Saw Palmetto:
This substance may be one of the most highly supplemented herbs, and with good reason
-- it does what it's supposed to do in that it reduces the symptoms of benign prostate
hypertrophy. Saw Palmetto works and I've used it and recommended it. The way in
which it works, however, may be deleterious to those who need it the most. Confused?
Stick with me a moment.
Saw Palmetto works by blocking the enzyme 5-alpha reductase, which is what allows for
the production of DHT (Dyhydrotestosterone). That's good, right? We've been hearing for
years how DHT is the bad testosterone and the culprit for everything from prostate
enlargement to baldness. Well, not only may that not be the case, but it looks like
everyone has been barking up the wrong tree. It's true, that reducing DHT will also
reduce inflammation of the prostate, not caused by an infection (prostatitis). But in doing
so there are far worse repercussions. DHT is more anabolic in nature than once believed,
but maybe more importantly is the fact that DHT is essential to achieving an erection!
The majority of consumers of Saw Palmetto have been older men -- those who are most
prone to prostate problems. But it's that very demographic who need what Saw Palmetto
takes away -- DHT - since erectile dysfunction is more prevalent among older men. So in
other words, using Saw Palmetto to cure prostate enlargement is like using decapitation
to cure a headache. It helps one problem but causes a bigger one.
There's something that has never been answered to my satisfaction: If testosterone and
DHT are the cause of all that's bad about being male, i.e., hair loss and prostate
enlargement, it would then be the bane of young men, since that's when levels are at their
highest. So why do older men with lowered testosterone and DHT develop baldness and
prostate hypertrophy? I've discussed this with several authorities in the field and the
usually reply is; "Good question."
I don't claim to have all the answers, but it shows that there's alot about this subject even
the medical world doesn't yet understand. In the meantime, I'd recommend staying away
from Saw Palmetto unless you experience acute symptoms of prostatitis or BPH. (Pain,
swolleness, scant and burning urination) It should not be taken on a regular basis.