PygeumPygeum africanum, African cherry bark

What it is

An extract of the bark of Prunus africana, the African cherry tree, used in French and Italian urology since the 1960s and available there as a prescription product rather than a supplement.

That European prescription history is why the trial literature exists at all, and also why most of it is old and published in French and Italian journals.

What the trials found

The systematic review pooled 18 randomised controlled trials covering 1,562 men. In the six placebo-controlled studies that reported data in a form that could be pooled, the combined improvement in symptoms and flow came to an effect size of minus 0.8 standard deviations, with a confidence interval from minus 1.4 to minus 0.3. That is a moderately large effect by the conventions of this kind of analysis.

The individual outcomes: men were more than twice as likely to report an improvement in overall symptoms, a risk ratio of 2.1 with a confidence interval of 1.40 to 3.1. Nocturia fell by 19 percent. Residual urine volume fell by 24 percent. Peak urine flow rose by 23 percent.

Taken at face value those are the best numbers of any ingredient on this site. The question is how much face value they deserve.

The problem with those numbers

Three details from the same review should temper the enthusiasm considerably. The first is that not every trial tested pygeum alone: the review included preparations that combined it with other plant extracts, and its authors called for future trials to use a standardized pygeum preparation.

The mean trial duration was 64 days, with a range of 30 to 122. These are short trials in a condition that fluctuates over months, and the longest of them is still shorter than the point at which saw palmetto's benefit evaporated.

More seriously, only one of the 18 trials reported a method of concealing treatment allocation, although 17 described themselves as double-blinded. Allocation concealment is the thing that stops researchers steering sicker or healthier patients into one arm, and its absence is one of the strongest known predictors of an inflated result. It is exactly the methodological weakness that made saw palmetto look effective for twenty years.

So the honest position is that pygeum has the best effect size in the category and the evidence quality that most often produces effect sizes that later shrink. That is why this page says moderate rather than strong.

The nocturia result

The 19 percent reduction in night-time urination is the finding most likely to matter in practice, because that is the symptom men actually want gone.

It also puts pygeum alongside rye grass pollen as one of the two ingredients here with a specific night-time result, and the two are worth comparing honestly. Rye grass pollen's finding is weaker in size but came from trials running 12 to 24 weeks. Pygeum's is larger but came from trials averaging nine. Neither has been tested properly since.

Dose and what to look for

The trials used varied preparations, most often 100 to 200 mg a day of bark extract, and the reviewers asked for future research to use standardized ones, which is a good reason to choose a product that states its standardization on the label. Powdered bark without a standardization figure is a different material from what was studied.

Once a day is fine. A randomised, double-blind trial in which 209 men completed the comparison set 50 mg twice a day against 100 mg once a day and found them equally effective over two months, with symptom scores improving by 38 and 35 percent and similar side effects. It had no placebo group, so it tells you about dose timing, not about whether pygeum works.

Labels listing thousands of milligrams usually describe something other than the extract. Some state a raw bark equivalent, calculated from the extraction ratio: a 4:1 extract means each milligram of extract came from four milligrams of bark, so a label claiming 4,000 mg of bark equivalent at 4:1 contains 1,000 mg of extract. That is still five to ten times the trial dose. Others list powdered bark, which is not standardized at all. Either way, the number to compare with the trials is the amount of standardized extract, and there is no trial data above 200 mg a day of it. More has not been shown to work better.

Pygeum is also a conservation problem, which most supplement pages do not mention. Prunus africana has been heavily harvested across its range and is listed under CITES Appendix II, meaning international trade is regulated. Sustainably harvested and cultivated sources exist and are worth preferring if a brand says where its bark comes from.

Most trials ran about two months, so give it at least that long. One uncontrolled follow-up reported further improvement out to a year, but there is no placebo-controlled data beyond about four months, and no long-term safety data under placebo control either.

Where it sits against the alternatives

On paper pygeum has the strongest numbers on this site. On evidence quality it sits behind beta-sitosterol, whose trials were double-blind and placebo-controlled with clearer reporting, and behind rye grass pollen, whose trials ran longer.

It sits far ahead of saw palmetto, which has the largest and best-conducted trials in the category and failed them.

If night-time urination is the problem, pygeum and rye grass pollen are the two to consider. If overall symptoms and flow are the problem, beta-sitosterol has the cleaner evidence.