Prostate problems are more common than many men might think, and they become even more common with age. In fact, benign prostatic hyperplasia is one of the most common medical conditions in older men. It occurs most often after the age of 50 and affects more than half of men by age 60; 90 percent are affected by age 85.¹ Cost for the treatment of BPH in the United States exceeds $2 billion annually and results in more than 300,000 surgical procedures each year to remove the prostate. 2

The prostate is a small gland that is part of the male reproductive system. The urethra—the tube that carries urine and semen—runs through the center of the prostate. When the prostate becomes enlarged (hyperplasia), it gradually squeezes the urethra. This can impede the flow of urine, causing symptoms such as urinary urgency, frequent urination (especially at night), difficulty urinating and sometimes pain. BPH does not lead to or cause cancer.

There are several theories as to what causes BPH, including infection, autoimmune response and pelvic muscle spasm.3 An enlarged prostate that is caused by infection is often treated with antibiotics, anti-inflammatory agents and neuromuscular agents.3 But an enlarged prostate that is not related to infection is sometimes difficult to treat.

Pharmaceutical medications such as finasteride and tamsulosin have been proven to relieve the symptoms of BPH, but are expensive and sometimes cause side effects. A number of herbal preparations, some of which have been carefully studied, also offer the promise of relief from BPH for lower cost and with less risk of adverse effects.

Saw palmetto
Saw palmetto (Serenoa repens) is used by more than 2 million men in the United States for treatment of BPH and is commonly recommended as an alternative to prescription drugs.4 It is widely used in Europe, where half of German urologists prescribe plant-based extracts over synthetic drugs.4 A 1998 review of 18 randomized controlled trials evaluated the effectiveness of saw palmetto extract for the treatment of BPH and compared it with the prescription drug finasteride.2 Trials included in the review lasted an average of nine weeks and involved almost 3,000 men. The studies assessed improvement in symptoms based on urological symptom scale scores and physician reports of improvement or worsening of symptoms. Only three studies reported results using standardized and validated urologic symptom scales. The studies used different doses and preparations of saw palmetto, and in some studies, saw palmetto was given in combination with other plant ingredients. However, the most frequently reported dosage was 160 mg of saw palmetto twice a day.

The researchers concluded that saw palmetto improved urinary flow and other symptoms as much as finasteride, and caused fewer side effects. (Finasteride can cause breast enlargement and tenderness, skin rash, swelling of the lips and erectile dysfunction.) Compared with those receiving placebo, men taking saw palmetto were nearly twice as likely to report improvement in symptoms. The authors later updated their review by adding three new trials involving another 230 men, and came to the same conclusion—that saw palmetto brings about mild to moderate improvements in urinary symptoms. 5

A more recent meta-analysis of 14 studies that ranged from three weeks to two years in duration all used the same standardized extract of saw palmetto. This analysis concluded that saw palmetto had a highly significant effect in improving BPH symptoms compared with placebo, as measured by the International Prostate Symptom Score, a standardized system for rating prostate symptoms.6 The majority of the studies administered a daily dose of 320 mg of the standardized extract.

A single double-blind, randomized study compared a daily dose of 320 mg of standardized extract of saw palmetto with the prescription drug tamsulosin and found that the saw palmetto extract was superior in reducing urinary symptoms of BPH.⁷ In this study, improvements were measured using the I-PSS scale.

Several mechanisms of action for saw palmetto have been suggested, including anti-androgenic (effects on male hormones), anti-inflammatory and antiproliferative effects, but exactly how it works has not yet been determined.8

Still, not all saw palmetto studies have had positive results. In a recent double-blind trial of 225 men over the age of 40 with moderate to severe symptoms of BPH, the men were given either 160 mg of saw palmetto extract twice a day or placebo for one year.4 The researchers found no improvement in signs and symptoms of BPH, including objective parameters such as urinary flow rate and prostate size, compared with placebo. The study used a water-soluble extract, rather than the fat-soluble extract used in most other studies, and applied a different scoring system for assessing the severity of symptoms, so it is difficult to compare these results with those of other studies. Nonetheless, urinary flow rate and prostate size were assessed in this study and no differences from placebo were seen. None of the studies have uncovered any major side effects from taking saw palmetto.

Pumpkin seed
Though extract of pumpkin seed (Cucurbita pepo) is often used for the treatment of BPH and is approved by the German Commission E for urinary problems associated with BPH, few clinical studies have investigated its effects, and even fewer are published in English.

Only one large, controlled, multicenter trial has looked at the effect of pumpkin seed extract alone on the treatment of BPH.9 In the study, 2,245 men with BPH received one or two capsules a day of a standardized preparation of pumpkin seed oil for 12 weeks. The I-PPS ratings decreased by 41 percent during therapy.

One randomized, double-blind, three-month Swedish study of 53 men used a combination formula of pumpkin seed and saw palmetto and concluded that those who received the preparation experienced significant improvement in urinary flow and frequency compared with those receiving a placebo.10 A recent study found that giving pumpkin seed oil with rats with experimentally induced BPH significantly improved prostate size compared with rats given corn oil.11

How pumpkin seed works in BPH is not yet known, but some experts have suggested that sterols in pumpkin seed oil may block testosterone, preventing the proliferation of prostate cells.¹² Animal studies have suggested the benefit may be related to improved function of the bladder and urethra, not a direct effect on the prostate itself.¹³ The average traditional daily dose of pumpkin seed is 10 g per day of ground seeds.¹⁴ No major side effects have been reported in clinical studies.

Stinging nettle root
Stinging nettle root (Urtica dioica) is used in Germany as a component of approved medicines for the treatment of BPH, though clinical trials on this application are lacking. Of those that have been published, few are in English. In a one-year, randomized, double-blind, placebo-controlled, multicenter German study, 246 patients were given either 459 mg a day of a dry extract of stinging nettle root or a placebo.¹⁵ In an English abstract of the study, the researchers concluded that stinging nettle can be considered a safe therapeutic option for reducing irritative symptoms associated with BPH. Specifically, the researchers reported a clinically significant reduction in I-PSS scores.

In a six-month observational study, 67 patients with BPH (age 53 to 87) were given an alcohol extract of stinging nettle combined with dog nettle (Urtica urens).¹⁶ The researchers concluded that symptoms such as frequent nighttime urination were alleviated, particularly in less severe cases of BPH.

Stinging nettle is also used as an ingredient in herbal blends for the treatment of BPH. In one six-month study, a proprietary blend of nettle root extract, saw palmetto extract and pumpkin seed oil was tested against placebo in 44 men age 45 to 80.17 The subjects receiving the herbal blend experienced improvements in clinical symptoms, but the findings were not deemed significant, possibly because of the small number of subjects in the study.

In a 24-week, prospective, double-blind, multicenter study of an herbal blend, 257 patients with BPH were given either two capsules a day containing a combination of 120 mg of stinging nettle root extract and 160 mg of saw palmetto extract, or placebo.18 Those who received the herbal blend experienced a substantial lessening of symptoms—even those with moderate and severe symptoms as measured by the I-PSS—compared with those receiving the placebo.

In another randomized, multicenter study of 431 patients, an herbal blend (120 mg of stinging nettle root extract and 160 mg of saw palmetto taken twice a day) was found to be as effective in relieving prostate symptoms as the prescription drug finasteride.19 The same herbal blend has also been found to be as effective as the drug tamsulosin, according to I-PSS scores.²⁰

Stinging nettle may act by inhibiting the action of testosterone.²¹ It has also been suggested that the polysaccharides it contains may have an anti-inflammatory effect. In addition, nettle contains beta-sitosterol, which itself has been studied as a BPH treatment.¹² No major side effects have been reported in any of the studies.

Pollen extract
Pollen extract is traditionally produced from pollen collected from the flowers of various plants. Anecdotal evidence and references from traditional herbal texts describe pollen extract's potent anti-inflammatory properties and potential in providing BPH symptom relief.22 Clinical investigations have provided some evidence that a rye grass pollen extract may result in improvement of BPH symptoms.23^,24

One systematic review of four BPH trials (two placebo-controlled and two comparative) evaluated the effectiveness of a proprietary preparation of 189 mg of rye grass pollen extract taken once a day.²⁴ Trials included in the review involved a total of 444 men and lasted 12 to 24 weeks. The reviewers concluded that the few studies available were limited by their short duration, small number of subjects, gaps in reported outcomes and unknown quality of pollen extract used. However, the available evidence suggested that the pollen extract modestly improved overall urologic symptoms associated with BPH, including frequent nighttime urination.

The most recently published trial looked at 58 BPH sufferers between the ages of 20 and 55 who took a different pollen extract preparation from the one used in all the trials in the systematic review.25 The results were based on the patients' evaluations of their symptoms, with the help of a questionnaire routinely used in the clinic where the study was conducted. The pollen supplement was found to be superior to placebo in providing relief for men with painful prostate symptoms, although the study had a number of methodological limitations. No major side effects were reported in any of the studies.

Other promising supplements
Other preparations have undergone less research, but have had some promising early findings. In a study of rats, red maca (Lepidium meyenii) was shown to reduce prostate size.26 Perennial pepperweed or peppergrass (Lepidium latifolium) has also been studied in rats and found to reduce prostate hyperplasia.²⁷

One small study found that 500 mg of the bioflavonoid quercetin given twice a day to 15 patients resulted in significant improvement in symptoms, compared with 13 men taking a placebo.28 Beta-sitosterol, a compound that is used to lower cholesterol, has also been studied for the treatment of BPH and found to decrease symptoms when given at doses of 60 to 130 mg per day.¹²

Fat-soluble compounds from the bark of the pygeum tree (Prunus africanum) have anti-inflammatory activity that may help relieve symptoms of BPH. A meta-analysis of 18 studies concluded that doses of 75 mg to 200 mg per day of the pygeum compounds provided significant improvement in urinary symptoms of BPH.29 However, because this African tree is considered endangered, it cannot be recommended as a BPH treatment.

Conclusions
Saw palmetto is the best researched of the herbs commonly recommended for treating BPH, and the evidence for its therapeutic benefit is strongest. The most recent well-controlled clinical trial failed to find benefit, but the previous positive findings of well-controlled trials cannot be ignored. Studies of pumpkin seed extract, stinging nettle root and rye grass pollen extract suggest that with additional research, these preparations may also offer a lower-risk, lower-cost option to prescription drugs for treating the symptoms of BPH.

Densie Webb, Ph.D., R.D., is a freelance writer and industry consultant based in Austin, Texas.

References
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