While more and more clinical trials support
the beneficial effects of saw palmetto on
prostate enlargement (benign prostatic hyperplasia, BPH), researchers have tried to determine the reason behind
the observed benefits. that is, how would saw palmetto act to relieve the symptoms of BPH?
BPH is caused by the over-growth of cells in the prostate gland. When the gland swells, it presses on the
urethra, which lies nextby, creating a sensation of need to urinate. Prostate cell growth is believed to be
promoted by a male sex hormone called dihydrotestosterone (DHT). DHT is converted from another male sex
hormone testosterone (T) by the action of an enzyme called 5-alpha-reductase. As men age, more DHT
is produced and may thus cause the prostate enlargement.
Here is where saw palmetto may fit in. It was shown some years ago that saw palmetto extract can inhibit the
function of 5-alpha-reductase in prostate cells cultured in dish in laboratories, meaning that saw palmetto can inhibit the
conversion of T into DHT, and thus lower the DHT level. As a result it may diminish prostate cell growth.
If this hypothesis is to hold, one may expect that BPH patients may have reduced
DHT levels after usage of saw palmetto. To test this idea, a group of researchers studied prostate samples
obtained from BPH patients who have taken 320 mg standardized saw palmetto extract for 3 months. They analysed
the concentration of T and DHT in various parts of the prostate gland1. What they saw was striking. In the
so-called periurethral region, whose enlargement causes urinary obstruction, DHT level is at average 2363 pg/g in patients
treated with saw palmetto whereas DHT level is at average 7317 pg/g in untreated patients. The DHT level reduction is statistically
very significant (P‹ 0.001). Meanwhile, The level of T is increased to 1023 pg/g in treated patients
from 615 pg/g in untreated patients. These results provided the key support on the hypothesis that
saw palmetto can inhibit 5-alpha-reductase in patients and indeed reduce the DHT production.
These findings are confirmed by another independent study 2 in which BPH patients were randomized to
receive either saw palmetto or placebo for 6 months. Here the levels of DHT in prostate were determined
before and after trial in both saw palmetto and placebo groups. Again DHT levels were reduced significantly
by 32% from 6.49 ng/g to 4.4 ng/g after saw palmetto treatment (P‹ 0.005) whereas no significant change
in the placebo group.
Therefore, these results strongly suggest that saw palmetto can effectively reduce the level of DHT in
patients with moderate BPH. This in turn may slow down the growth of prostate cells and thus relieve
the symptoms of BPH. Saw palmetto thus may represent an efficient tool to maintain the DHT level in aging
men.
Reference
1.Di Silverio F, Monti S, Sciarra A, Varasano PA, Martini C, Lanzara S, D'Eramo G, Di
Nicola S, Toscano V. Effects of long-term treatment with Serenoa repens (Permixon) on the
concentrations and regional distribution of androgens and epidermal growth
factor in benign prostatic hyperplasia. Prostate. 1998 Oct
1;37(2):77-83.
2. Marks LS, Hess DL, Dorey FJ, Luz Macairan M, Cruz Santos PB, Tyler VE. Tissue effects of saw palmetto and finasteride: use of biopsy cores for in situ
quantification of prostatic androgens. Urology. 2001
May;57(5):999-1005.
