by Thomas Incledon, PhD(c), RD, LD/LN, RPT, NSCA-CPT, CSCS
Introduction
Go into any bookstore or search through any book web-site and you’ll find numerous books on herbs and herbal remedies. One herb that has received a significant amount of attention is Saw palmetto. Its use in treating prostatic ailments has also been covered in popular newspapers, on radio programs, and on TV. However, many times consumers are given incomplete or misleading information. Saw palmetto contains numerous active and inactive agents, which may or may not alleviate prostatic ailments, depending on the cause of the problem. Consumers should be aware of these issues before trying this product so they can use it appropriately in conjunction with the approval of their physician.
Saw palmetto
Saw palmetto is scientifically referred to as Serenoa repens. It is a plant that can be found in the United States along the southern coastal regions of South Carolina, Georgia, Florida, and California. The medicinal components of the plant are found in its fruit. The ripened fruit can be consumed dried, partially dried, and/or fresh to obtain the active components [1]. The isolated ingredients include sterols (plant steroids) [1], various fatty acids, sugars, beta carotene, lipase, tannin, vanillic acid, vanillin, and other chemicals [2]. It is believed to relieve symptoms associated with benign prostatic hypertrophy (BPH) in men.
Benign Prostatic Hypertrophy
The prostate is a single doughnut shaped gland about the size of a chestnut [3]. It is located just below the urinary bladder and surrounds the prostatic urethra. The secretions of the gland enter the prostatic urethra through the prostatic ducts and contribute to sperm motility and viability. At birth the gland weighs only a few grams. The increase in androgen concentrations associated with puberty, primarily dihydrotestosterone (DHT), contributes to the enlargement of the prostate. Around the age of 20, the prostate reaches its adult weight of about 20 grams [4]. The weight and size of the prostate is usually stable until about the age of 50, when a second growth spurt can occur. This growth spurt occurs in different regions of the prostate and can lead to urinary tract obstruction and constipation [4].
In men, testosterone (T) can be converted into DHT in prostatic cells by the enzyme 5-alpha-reductase. DHT then stimulates cellular growth and division leading to the prostatic enlargement. Based upon research on dogs, it is thought that the androgen DHT increases prostate size, while the estrogen estradiol enhances the action of DHT [5]. Unfortunately, studies with humans or human cell cultures have not been able to support this evidence [6-9]. This is important because it indicates that the exact mechanisms (the cause and effect of prostatic hypertrophy) have eluded researchers. One way to prevent BPH is for men 50 and over to get an annual prostate-specific antigen (PSA) test. The amount of PSA increases with the size of the prostate and can indicate infection, benign enlargement, or prostate cancer.
Research on Saw palmetto
Studies using cell cultures have indicated that Saw palmetto can block the binding of DHT and T to androgen receptors [10, 11]. By blocking the binding of these hormones, it is thought that prostatic cell growth can be slowed and therefore symptoms of BPH can be reduced. Other research on cell cultures indicates that Saw palmetto can inhibit the actions of the enzyme that converts T into DHT [12-14]. While these types of studies are important because they help researchers understand how Saw palmetto may potentially alleviate BPH, they do not tell us if it actually works in humans.
Studies on humans indicate that Saw palmetto does not affect plasma T concentrations [15] and may work as an antiestrogen [16]. In a recent study, a significant improvement in subjective measures was reported for BPH patients after 2 months of Saw palmetto treatment [17]. However, there were no significant changes in objective measures such as peak urinary flow rate, post-void residual urine volume, or mean serum PSA levels [17]. A recent review published in the Journal of the American Medical Association (JAMA) indicated that many of the studies on Saw palmetto (Serenoa repens) were of short duration and varied in study design and the type of treatment offered. Nonetheless, the evidence did suggest that Serenoa repens improved urologic symptoms and flow measures [18]. The review article goes on to conclude that compared with a commonly prescribed drug, Saw palmetto produced similar improvement in urinary tract symptoms and urinary flow. It also was associated with a fewer number of side effects.
Side Effects and Dosages
As reported in the JAMA article, another recent review on herbal supplements indicated that Saw palmetto is generally considered to be safe [19]. Typical dosages of the plant extract are 160 mg taken twice per day [17, 20]. It should be pointed out that since many of the components of Saw palmetto are fat soluble, common herbal preparations of teas or tinctures would not work well for administering this product since the active ingredients would not dissolve in the water. Capsules should be taken with food containing some fat or oil to allow for absorption of the lipid soluble components.
The Unknown
Exactly what causes BPH is still a matter of debate. Scientific evidence indicates that DHT and estradiol are important factors. Plasma levels of DHT and estradiol don’t always indicate the presence or absence of BPH. It is possible that blood concentrations and/or the actions of these hormones are greater in prostatic tissue than in the blood. Saw palmetto (Serenoa repens) appears to be potentially useful in alleviating subjective measures of BPH. In addition, treatment therapies combining estrogen blockers, androgen blockers, and perhaps alpha receptor blockers may prove useful [21]. Unfortunately, there has been little research on the effects of herbal supplements incorporating this type of multidimensional approach. While Saw palmetto may be safe, consumers need to be cautious of products that contain other agents that may not be considered safe. Many anti-BPH herbal products contain a variety of herbs and other supplements. Most of the studies done to date have been on the Saw palmetto extract by itself and not in conjunction with other agents, such as Pygeum africanum. Pygeum africanum is another herbal extract that may have a potential benefit in the treatment of BPH [22]. However, just because these agents work separately, does not indicate they will work together. Future studies should not only establish the long term safety of Saw palmetto, but also its safety when taken as part of a mixture containing other phytochemicals.
Since one current trend in avoiding disease is prevention, it would seem logical for men 50 and older to want to take Saw palmetto to reduce their chances of developing BPH. Keep in mind though that the research to date is limited to men having BPH already, taking Saw palmetto, and then having an alleviation of BPH symptoms (usually pain when urinating). While Saw palmetto does prevent or decrease prostatic cells in cell culture-type studies, this does not mean it will do the same for men. In addition, the longest studies have lasted less than a year. A preventative program of Saw palmetto when there are no signs of BPH could mean years of unnecessary treatment. The wisest approach based upon current scientific information is to obtain regular, annual PSA check-ups. If the PSA count is high according to your doctor, then ask about taking Saw palmetto. At this point, it should be taken alone and not in conjunction with other treatments until there is more data available. Although Saw palmetto will not decrease PSA levels, your doctor can perform the necessary follow-up exams to determine if the treatment is working.
References
1. Medical Economics Company. PDR for herbal medicines. 1998, Montvale, NJ: Medical Economics Company.
2. Duke, J.A., Handbook of phytochemical constituents of GRAS herbs and other economic plants. 1992, Boca Raton: CRC Press.
3. Guyton, A.C. and J.E. Hall. Textbook of medical physiology. 9th ed. 1996, Philadelphia: W.B. Saunders.
4. Wilson, J.D., et al., Williams’ textbook of endocrinology. 9th ed. 1998, Philadelphia: W.B. Saunders Co.
5. Aumuller, G., et al., Phenotypic modulation of the canine prostate after long-term treatment with androgens and estrogens. Prostate, 1982. 3(4): p. 361-373.
6. Meikle, A.W., J.A. Smith, and J.D. Stringham, Estradiol and testosterone metabolism and production in men with prostatic cancer. J Steroid Biochem, 1989. 33(1): p. 19-24.
7. Nakhla, A.M. and W. Rosner, Stimulation of prostate cancer growth by androgens and estrogens through the intermediacy of sex hormone-binding globulin. Endocrinology, 1996. 137(10): p. 4126-4129.
8. Luo, D., et al., Effect of prostatic growth factor, basic fibroblast growth factor, epidermal growth factor, and steroids on the proliferation of human fetal prostatic fibroblasts. Prostate, 1996. 28(6): p. 352-358.
9. Levine, A.C., et al., The effect of androgen, estrogen, and growth factors on the proliferation of cultured fibroblasts derived from human fetal and adult prostates. Endocrinology, 1992. 130(4): p. 2413-2419.
10. Sultan, C., et al., Inhibition of androgen metabolism and binding by a liposterolic extract of “Serenoa repens B” in human foreskin fibroblasts. J Steroid Biochem, 1984. 20(1): p. 515-519.
11. el-Sheikh, M.M., M.R. Dakkak, and A. Saddique, The effect of Permixon on androgen receptors. Acta Obstet Gynecol Scand, 1988. 67(5): p. 397-399.
12. Bayne, C.W., et al., Serenoa repens (Permixon((R))): A 5alpha-reductase types I and II inhibitor-new evidence in a coculture model of BPH. Prostate, 1999. 40(4): p. 232-241.
13. Iehle, C., et al., Human prostatic steroid 5 alpha-reductase isoforms—a comparative study of selective inhibitors. J Steroid Biochem Mol Biol, 1995. 54(5-6): p. 273-279.
14. Delos, S., et al., Testosterone metabolism in primary cultures of human prostate epithelial cells and fibroblasts. J Steroid Biochem Mol Biol, 1995. 55(3-4): p. 375-383.
15. Casarosa, C., M. Cosci di Coscio, and M. Fratta, Lack of effects of a lyposterolic extract of Serenoa repens on plasma levels of testosterone, follicle-stimulating hormone, and luteinizing hormone. Clin Ther, 1988. 10(5): p. 585-588.
16. Di Silverio, F., et al., Evidence that Serenoa repens extract displays an antiestrogenic activity in prostatic tissue of benign prostatic hypertrophy patients. Eur Urol, 1992. 21(4): p. 309-314.
17. Gerber, G.S., et al., Saw palmetto (Serenoa repens) in men with lower urinary tract symptoms: effects on urodynamic parameters and voiding symptoms. Urology, 1998. 51(6): p. 1003-1007.
18. Wilt, T.J., et al., Saw palmetto extracts for treatment of benign prostatic hyperplasia: a systematic review [published erratum appears in JAMA 1999 Feb 10;281(6):515] [see comments]. Jama, 1998. 280(18): p. 1604-1609.
19. Klepser, T.B. and M.E. Klepser, Unsafe and potentially safe herbal therapies. Am J Health Syst Pharm, 1999. 56(2): p. 125-138.
20. Di Silverio, F., et al., 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. 37(2): p. 77-83.
22. Breza, J., et al., Efficacy and acceptability of tadenan (Pygeum africanum extract) in the treatment of benign prostatic hyperplasia (BPH): a multicentre trial in central Europe. Curr Med Res Opin, 1998. 14(3): p. 127-139.
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