Pollen Extract for BPH (Benign Prostatic Hyperplasia)

Rye grass pollen extract may modestly ease the urinary symptoms of benign prostatic hyperplasia (BPH), especially getting up at night to urinate, but the trials behind it are small, short and old. A systematic review of four controlled trials in 444 men, lasting 12 to 24 weeks, found men taking the extract were more likely than men on placebo to rate their symptoms as satisfactory or improving (risk ratio 2.40) and had less nocturia, or night-time urination (risk ratio 2.05) [1].

The same review found no improvement in urine flow, the urine left in the bladder or prostate size compared with placebo or the comparison products [1]. In the largest randomised trial, of 243 men, the alpha-blocker tamsulosin, alone or with the extract, appeared more effective than the extract alone: symptom scores improved in every group, but flow improved only with tamsulosin [3]. That is why we rate it mixed: a plausible symptom benefit, without the objective changes or modern trials needed to call it likely. Its use for chronic pelvic pain is covered on pollen extract for prostatitis.

In laboratory tests, the fat-soluble fraction of a rye pollen extract inhibited cyclo-oxygenase and 5-lipoxygenase, two enzymes that make inflammatory messengers (prostaglandins and leukotrienes), at concentrations similar to the anti-inflammatory drug diclofenac; the water-soluble fraction had no effect [14]. The authors suggested an anti-congestive, anti-inflammatory action as the best explanation for its use in prostate disease [14].

Other cell studies point to an anti-growth effect. A purified fraction of the extract, identified as a compound called DIBOA, slowed the growth of prostate cancer cells and of cultured prostate stromal and epithelial cells, although the cultured prostate cells needed higher concentrations [15]. In prostate cell lines, the extract reduced androgen receptor and PSA protein levels in stromal cells and slowed cell growth [16].

All of this comes from cells in a dish. In men, the controlled trials found no change in prostate size compared with placebo [1], so these findings explain why the extract was studied, not whether it shrinks the prostate.

Doses varied between trials and products. In a long-term study of 79 men, the extract was taken as 126 mg (two 63 mg tablets) three times a day for more than 12 weeks [4]. A Chinese randomised trial gave 240 men 750 mg or 375 mg twice a day for 4 years: the higher dose improved symptom scores by 3 months (the lower dose by 6 months), improved prostate volume, flow and residual urine more, and was followed by fewer episodes of urinary retention (5 vs 16) and surgery (2 vs 8) [5]. That trial had no placebo group, so it shows the higher dose did better than the lower one, not that either beat no treatment.

The controlled trials in the systematic review lasted 12 to 24 weeks [1], and the placebo-controlled trial by Buck and colleagues ran for 6 months [2]. Products differ: the European Association of Urology (EAU) guideline warns that extracts of the same plant from different makers don't necessarily have the same effects [17], so a standardised rye grass pollen extract is the closest match to the evidence.

The best summary is a 2000 systematic review of four trials in 444 men: two compared the extract with placebo and two with other products (the plant extract Tadenan and Paraprost, an amino-acid mixture), for 12 to 24 weeks [1]. Men on the extract were more likely to report satisfactory or improving symptoms than men on placebo (risk ratio 2.40, 95% CI 1.21 to 4.75), and nocturia improved (risk ratio 2.05, 1.41 to 3.00) [1].

There was no improvement in urine flow rates, residual urine or prostate size compared with placebo or the other products [1]. The reviewers noted short, small trials, unclear concealment of treatment allocation in all of them, gaps in reported outcomes, preparations of unknown quality and comparison products with no proven effect [1].

In a 6-month double-blind trial of 60 men with outflow obstruction, 69% improved subjectively on the extract versus 30% on placebo; residual urine and the front-to-back diameter of the prostate on ultrasound decreased, but flow rate and voided volume didn't differ significantly [2]. A Japanese double-blind trial against Paraprost in 192 men found no significant difference in overall effectiveness (49.1% vs 41.2%) [6], and a 4-month comparison with Tadenan in 89 men reported subjective improvement in 78% versus 55%, with a smaller prostate volume within the extract group [7].

Uncontrolled studies report improvements too. In 79 men, maximum flow rose from 9.3 to 11 mL/s and residual urine fell from 54.2 mL to under 30 mL; prostate volume didn't change overall, though the 28 men treated for over a year had a mean volume of 26.5 cm3, against a starting average of 33.2 cm3 for the whole group [4]. Without a placebo group, changes like these can't be separated from the natural ups and downs of symptoms. After prostate surgery (TURP) in 100 men with inflamed prostate tissue, men given the extract for 3 months had significantly different storage-symptom, quality-of-life and erectile-function scores from placebo at 6 months, with effects varying by symptom severity [13].

The largest randomised trial compared the extract, the alpha-blocker tamsulosin and the two together for 12 weeks in 243 men [3]. Symptom scores improved in every group, but flow rates rose significantly only in the groups taking tamsulosin, and the authors concluded that tamsulosin alone or the combination seemed more effective than the extract alone [3].

Many products mix pollen extract with other ingredients. In a 3-month double-blind trial that randomised 144 men, a blend of rye grass pollen extract, saw palmetto, beta-sitosterol and vitamin E reduced nocturia and daytime frequency and improved the AUA symptom score versus placebo, with no differences in flow, residual urine or PSA [10]; that result can't be credited to the pollen extract alone. Pollen extract with teupolioside has only uncontrolled studies: IPSS fell from 14 to 10 over 3 months in 53 men [11], and improved in a 25-man pilot [12].

We found no large, modern placebo-controlled trial of pollen extract alone for BPH. A 2008 review in the Journal of Urology found rye pollen improved symptoms but not flow rates and had yet to be evaluated in a trial of sound methodology [8]. A 2019 umbrella review concluded that flower pollen extracts may be useful as a complementary remedy for BPH, and that evidence on bee pollen is too limited to draw any conclusion [9]; see bee pollen for that product.

For men with mild or moderate symptoms who are minimally bothered, the EAU guideline recommends watchful waiting, with lifestyle advice and self-care information [17]. For moderate to severe symptoms it recommends alpha-blockers, and 5-alpha-reductase inhibitors for men at higher risk of progression, such as a prostate larger than 40 mL [17]. It offers hexane-extracted saw palmetto, as a weak recommendation, to men who want to avoid side effects, especially sexual ones, and says to tell them the benefit may be modest [17].

Our pages on saw palmetto for BPH, pygeum for BPH and nettle root for BPH cover the other plant options.

Pollen extract was well tolerated in the BPH trials. Adverse events were rare and mild, and 4.8% of men stopped the extract compared with 2.7% on placebo [1]. No adverse reactions were seen in the 79-man long-term study [4] or in the 4-year dose comparison, where PSA did not change significantly in either group [5]. The trial abstracts don't report allergy outcomes, so if you have a pollen allergy, ask a clinician before trying it.

The bigger risk is delay. Urinary symptoms can come from infection, blood in the urine or diabetes as well as the prostate, which is why guidelines call for a urine test, and a PSA test when it would change management [17]. BPH can also progress to urinary retention, being unable to empty the bladder: the 4-year trial recorded 21 episodes among its 240 men [5], and recurrent retention is a reason for surgery [17].

We found no interaction studies for pollen extract in people. In one randomised trial it was taken with tamsulosin for 12 weeks, but the abstract gives no safety results for the combination [3]. In cell studies the extract lowered PSA protein levels [16], while in the 4-year trial PSA in the blood didn't change [5]; tell your doctor you take it before a PSA test.